CN109689267B - Method and apparatus for building metal objects by solid freeform fabrication with two welding torches - Google Patents

Abstract

A system and method for manufacturing objects, particularly titanium and titanium alloy objects, by solid freeform fabrication is provided, wherein the deposition rate is increased by using two separate heat sources, one for heating the deposition area on the substrate and one for heating and melting a metallic material, such as a wire or a powdered metallic material.

Description

Method and apparatus for building metal objects by solid freeform fabrication with two welding torches

RELATED APPLICATIONS

Us patent application serial No. 14/008,307 entitled "method and apparatus for building metal objects by solid freeform fabrication" filed 2013, 9, 27, which is the U.S. national phase of international patent application No. PCT/NO2012/000033 entitled "method and apparatus for building metal objects by solid freeform fabrication" filed 2012, 3, 30, 2011, which claims priority to uk patent application No. GB 1105433.5 entitled "method and apparatus for building metal objects by solid freeform fabrication" filed 2011, 3, 31, the subject matter of each of which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a method and apparatus for manufacturing objects, in particular titanium and titanium alloy objects, by solid freeform fabrication.

Background

Structured metal parts made of titanium or titanium alloys are usually made by casting, forging or machining from a billet. The disadvantages of these techniques are the large use of expensive titanium metal materials and the long manufacturing lead times.

Fully dense physical objects can be manufactured by manufacturing techniques known as rapid prototyping, rapid manufacturing, layered manufacturing, Solid Free Form Fabrication (SFFF), additive manufacturing, and 3D printing. The technique uses Computer Aided Design (CAD) software to first build a virtual model of the object to be fabricated, and then convert the virtual model into thin, parallel slices or layers that are generally horizontally oriented. The physical object may then be manufactured by lofting or preforming a continuous layer of raw material in liquid, paste, powder or other layerable, spreadable or fluid form (such as molten metal, e.g. from molten welding wire) into a sheet of material shaped like a virtual layer until the entire object is formed. The layers may be fused together to form a solid dense object.

Solid freeform fabrication is a flexible technique that allows the formation of objects of almost any shape at relatively fast production rates, which typically range from hours to days for each object. Thus, the technique is suitable for prototype formation and small volume production, and can be scaled up for large volume production.

The layered manufacturing technique may be extended to include the deposition of sheets of build material, i.e. each structural layer of the virtual model of the object is divided into a set of sheets which, when placed side by side, form the layers. This allows the metal object to be formed by welding metal wires to the substrate in a continuous strip forming each layer according to a virtual layered model of the object and repeating the process for each layer until the entire physical object is formed. The accuracy of the welding technique is often too rough to directly form an object of acceptable dimensions. Thus, the formed object is generally considered to be a green object or preform that needs to be processed to an acceptable dimensional accuracy.

Electron beam freeform fabrication is known in the art (see, for example, Taminger et al (published on the 13 th solid freeform fabrication workshop held by Austin, Texas, 8.5.7.2002, "characteristics of 2219 aluminum made by Electron Beam freeform fabrication"; proceedings of the division of Austin, Texas university (2002); Taminger et al (published on 9.9.10.2003, third annual meeting of automotive composites conference proceedings of Troy, Mich., 6. "Electron Beam freeform fabrication: Rapid Metal deposition Process" society of Plastic Engineers (2003), and Taminger and Haflger ("Electron Beam freeform fabrication for cost-efficient near-net-shape fabrication", NATO/RTOAVT-139 for a conference of experts on cost-efficient fabrication by Net-shape processing (Naey, Naey) (NATO), pages 9-25)). Taminger and Hafley (2006) describe a method and apparatus for fabricating structural metal parts directly from computer-aided design data in conjunction with electron beam freeform fabrication (EBF). The structural component is built up by welding on successive layers of metal wire which is welded by the thermal energy provided by the electron beam. The EBF process involves feeding a wire into a pre-heating zone or molten pool formed and maintained by a focused electron beam in a high vacuum environment. Positioning of the electron beam and the welding wire is achieved by movably articulating the electron beam gun and the actuator of the support base plate along one or more axes (X, Y, Z and rotation) and adjusting the position of the electron beam gun and the support base plate by a four axis motion control system. The process is said to be nearly 100% efficient in material use and 95% efficient in power consumption. The method can be used for bulk metal deposition and for more detailed deposition, and has a significant impact on the requirements for shorter lead times and reduced material and processing costs compared to conventional metal part processing methods.

It is known to use a plasma arc to provide heat for welding metallic materials. The method can be used at atmospheric pressure or higher and thus allows the use of simpler and cheaper process equipment. One such method is known as gas tungsten arc welding (GTAW, also denoted as Tungsten Inert Gas (TIG) welding), in which a plasma transferred arc is formed between a non-consumable tungsten electrode and the welding area. The plasma arc is typically protected by a gas supplied by a plasma torch that forms a protective cover around the arc. TIG welding may include feeding a wire or metal powder into a molten pool or plasma arc as a filler.

It is known to build objects by Solid Free Form Fabrication (SFFF) using a TIG torch (see, for example, U.S. patent publication No. 2010/0193480 to Adams) in which a continuous layer of metallic feedstock material having low ductility is applied to a substrate. The plasma stream is generated by exciting a flowing gas using an arc electrode having a variable amplitude current supplied thereto. Prior to deposition, a plasma stream is directed to the predetermined target area to preheat the predetermined target area. The current is regulated and feedstock material (such as wire) is introduced into the plasma stream to deposit the molten feedstock material in a predetermined target area. The current is regulated and the molten feedstock is slowly cooled at an elevated temperature, typically above the brittle-to-ductile transition temperature of the feedstock material, during the cooling stage to minimize the possibility of material stress occurring.

Withes et al (U.S. patent publication No. 2006/185473) also describes the use of a TIG torch instead of the expensive laser traditionally used in SFFF processes, which has a relatively low cost titanium feed, by combining the titanium feed and the alloy components in a manner that significantly reduces the cost of the raw materials. Withers et al teach that non-alloyed commercial pure titanium wires (CP titanium wires) can be used that are less costly than alloy wires, and that CP titanium wires can be used in combination with powder alloy components in situ in an SFFF process by combining the CP titanium wires with the powder alloy components in a torch melt or other high power energy beam. Witer et al also teaches that titanium sponge materials can be mixed with alloying elements and formed into wires, which can be used in combination with a plasma torch or other high power energy beam in an SFFF process to produce near net shape titanium parts.

Abbott et al (WO 2006/133034, 2006) describe a direct metal deposition process for fabricating complex three-dimensional shapes using a laser/arc hybrid process, which includes the steps of providing a substrate and depositing a first molten metal layer from a metal feedstock on the substrate using laser radiation and an arc. The arc may be provided by a gas metal arc torch using a metal feedstock as an electrode. Abbott et al teach that the use of laser radiation in combination with gas metal arc welding can stabilize the arc and purportedly provide higher process rates. Abbott et al use a consumable electrode guided by and out of a wire guide. The metal of the consumable electrode melts at the tip and the molten metal is deposited by positioning the tip at a deposition point. The heat required to melt the consumable electrode can be provided by an electric arc expanding between the tip of the electrode and the workpiece/deposition substrate and by laser irradiation of the deposition area. Welding by melting a consumable electrode heated by an arc is known as Gas Metal Arc Welding (GMAW), which is also known as metal inert gas welding (MIG welding) where an inert gas is used to form the arc.

Titanium metal or titanium alloys heated to above 400 c may oxidize when contacted with oxygen. Accordingly, there is a need to protect welds and heated objects formed by layered freeform fabrication from oxygen in the ambient atmosphere.

Guldberg (WO2011/019287) teaches a solution to this problem, which discloses a method of increasing the deposition rate by fabricating objects, particularly titanium and titanium alloy objects, by SFFF in a reactor chamber closed to the ambient atmosphere. By making the deposition chamber sufficiently oxygen-free, it is no longer necessary to take protective measures to avoid oxidation of the new weld area by ambient atmospheric oxygen, so that the welding process can be carried out at a higher speed, since the weld area can be allowed to have a higher temperature without the risk of excessive oxidation of the weld bead. For example, in the production of objects of titanium or titanium alloys, it is no longer necessary to cool the weld zone below 400 ℃ to avoid oxidation.

Another solution to increase the deposition rate is known from Keicher et al (us patent No. 6,268,584), which discloses a deposition head assembly comprising the following features: an array of output powder nozzles for generating converging powder streams to a deposition area; a central aperture that allows focusing of the plurality of beams onto a deposition substrate; and a coaxial gas flow for each powder nozzle that concentrates the powder flow from the nozzles to provide a longer working distance between the nozzle and the deposition head assembly. A longer working distance is critical to ensure that the molten metal particles do not adhere to the deposition equipment during processing. Specifically, Keicher et al describes a manifold system designed into the deposition head assembly that can use more than one laser beam simultaneously for the deposition process. The deposition head assembly also includes means for actively concentrating the powder flow from each orifice to improve material utilization efficiency.

Abbott et al (WO 2006/133034) describe another solution to the problems associated with the reactive nature of molten titanium, which describes the use of a combination of gas metal arc and laser welding. Gas metal arc techniques have several drawbacks that severely limit their application in depositing titanium. These include instability of metal transfer, excessive sputtering and poor control of the deposited layer shape, and high heat input that causes deformation of the thin slices during deposition. Also, it is impossible to improve productivity due to drift of cathode spots occurring during deposition. The solution to these problems according to Abbott et al relates to a direct metal deposition process comprising the steps of providing a substrate and depositing metal from a metal feedstock onto the substrate. An arc is generated between the metal feedstock and the substrate, and the arc is exposed to laser radiation to form a pool of molten metal on the substrate. The molten metal pool is cooled to form a first solid metal layer on the substrate.

The problem to be solved is the speed at which material is deposited on a substrate to form a workpiece. The temperature of the wire may be increased to preheat the wire to melt at a faster rate. However, higher temperatures can result in spray transfer or splashing or uncontrolled addition of molten metal from the molten electrode into the molten metal bath, resulting in poor deposition and inability to control the shape of the deposited layer. Too high a temperature of the preheating zone or of the bath can also lead to deformation of the thin layer during deposition.

Accordingly, there is a need in the art for an economical method of direct metal deposition with increased metal deposition rates. There is also a need in the art for a method of increasing the throughput and yield of direct metal deposition formed products.

Disclosure of Invention

It is an object of the present invention to provide an apparatus for building a metal object by SFFF.

It is another object of the invention to provide a method for rapid layered manufacturing of objects in titanium or titanium alloys.

The present invention addresses the need for an improved, economical method of performing direct metal deposition. The present invention further addresses the need for a method of increasing the throughput and throughput of distortion-free direct metal deposition formed parts having smooth, well-defined deposition boundaries.

The invention is based on the following recognition: the deposition rate may be increased by using a dual torch system, which may include, for example, a first torch for preheating a target deposition area on the substrate and a second torch for heating and melting the wire. Various combinations of first and second torches may be used. The first torch may include a laser device for preheating a target deposition area on the substrate, and the second torch may include a Plasma Arc (PAW) torch, such as a Plasma Transferred Arc (PTA) torch, for heating and melting the wire onto the target deposition area on the substrate. The first welding torch may comprise a PAW welding torch, such as a PTA welding torch, for preheating a target deposition area on the substrate, and the second welding torch may comprise a laser device for heating and melting the wire onto the target deposition area on the substrate. The first torch may include a first laser device for preheating a target deposition area on the substrate, and the second torch may include a second laser device for heating and melting the wire onto the target deposition area on the substrate. The first torch may include a laser device for preheating a target deposition area on the substrate, and the second torch may include a coaxial powder feed nozzle laser system for heating and melting the metal powder onto the target deposition area on the substrate. The first torch may comprise an electron beam device for preheating a target deposition area on the substrate, and the second torch may comprise a laser device for heating and melting the wire onto the target deposition area on the substrate. The first torch may comprise a laser device for preheating a target deposition area on the substrate, and the second torch may comprise an electron beam device for heating and melting the wire onto the target deposition area on the substrate. The first torch may include a first electron beam device for preheating a target deposition area on the substrate, and the second torch may include a second electron beam device for heating and melting the wire onto the target deposition area on the substrate.

The present invention provides a system for building a metal object by solid freeform fabrication, the system comprising: a first welding gun for preheating the substrate at a position where the metal material is to be deposited; a second torch for melting the metal source into droplets of the metallic material deposited on the pre-heating region of the substrate; an actuator tray to move the substrate relative to at least the first torch, or an actuator arm to move the second torch, or any combination of these actuators; and a control system capable of reading a computer-aided design (CAD) model of the object to be formed and employing the CAD model to adjust the position and motion of the system for positioning and moving the substrate and operating the welding torch such that the physical object is built by fusing successive deposits of metallic material to the substrate.

The first torch preheats the substrate to accept a molten metal wire droplet at a location where molten metal material is to be deposited. In some embodiments, at least a portion of the substrate may be melted by the first torch to make the substrate more receptive. In some embodiments, the first torch applies sufficient heat to form a pre-heated region in the substrate at the location where the metallic material is to be deposited. In some embodiments, the second torch applies sufficient heat to form a molten pool in the substrate at the location where the metallic material is to be deposited. It is noted that although the present invention is described in relation to the use of wires, any conductive structure that can be guided and melted to deposit material may be used, for example, consumable electrodes of any suitable size and shape may be used.

The first welding torch may promote fusion between the substrate and the molten metallic material by deepening the melting in the substrate. The first welding torch may help to ensure sufficient melting of the overheated molten metal material, which may not be able to achieve sufficient melting by itself.

The system may include: a PAW torch, such as a PTA torch, as a first torch; and a laser device as a second welding gun. In such a system, the PAW torch may be electrically connected to a dc power supply such that the electrode of the PAW torch becomes the cathode and the wire becomes the anode.

The second torch may also be designed to contribute heat energy in the preheat zone. Also, the first and second torches may be located on opposite sides of the substrate.

There is also provided a method for manufacturing a three-dimensional object of metallic material by solid freeform fabrication, wherein the object is made by fusing together successive deposits of metallic material onto a substrate, the method comprising: preheating at least a portion of a surface of a substrate, such as at a location where a metallic material is to be deposited, using a first torch; heating and melting the metallic material using a second welding torch such that the molten metallic material is deposited onto the preheated region of the substrate; and moving the substrate in a predetermined pattern relative to the position of the first and second welding torches such that the continuous deposit of molten metallic material solidifies and forms a three-dimensional object.

The methods provided herein may use a PAW torch (such as a PTA torch) as the first torch and a laser device as the second torch. The methods provided herein may use a laser device as the first welding gun and a PAW welding torch as the second welding gun. In such a system, the PAW torch may be electrically connected to a dc power supply such that the electrode of the PAW torch becomes the cathode and the wire becomes the anode.

The methods provided herein can use a first laser device as a first welding torch and a second laser device as a second welding torch. The methods provided herein can use a laser device as a first torch and a coaxial powder feed nozzle laser system as a second torch. The methods provided herein can use an electron beam device as the first torch and a laser device as the second torch. The methods provided herein can use a laser device as the first torch and an electron beam device as the second torch. The methods provided herein can use an electron beam device as the first torch and a laser device as the second torch. The methods provided herein can use a first electron beam device as a first torch and a second electron beam device as a second torch.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. For clarity, the drawings are not to scale and some components are omitted.

In the drawings:

FIG. 1 is a reproduction of FIG. 1 of Taminger and Hafley ("Electron Beam free form fabrication for cost-effective near-net shape fabrication", NATO/RTOAVT-139 on an expert conference for cost-effective fabrication by net shape processing (NaTO, pp. 9-25) showing a schematic of the principle of solid free form fabrication.

Fig. 2 is a reproduction of fig. 1 of US 2006/0185473 showing a schematic view of the principle of plasma transferred arc solid freeform fabrication.

Fig. 3 is a schematic diagram showing a cross-sectional view of an apparatus according to a second aspect of the invention.

Fig. 4 is a schematic diagram showing a cross-sectional view of a second embodiment of the present invention including a heat pulse.

Fig. 5 is a schematic side view of an embodiment of a dual torch system provided herein, including a laser apparatus for preheating a target deposition area on a substrate, and a plasma delivery arc for heating and melting a wire onto the target deposition area on the substrate.

Fig. 6 is a schematic side view of an embodiment of a dual torch system provided herein that includes a plasma transferred arc for preheating a target deposition area on a substrate and a laser apparatus for heating and melting a wire onto the target deposition area on the substrate.

Fig. 7 is a schematic side view of an embodiment of a dual torch system provided herein that includes a laser apparatus for preheating a target deposition area on a substrate and a laser apparatus for heating and melting a wire onto the target deposition area on the substrate.

Fig. 8 is a schematic side view of an embodiment of a dual torch system provided herein that includes a laser apparatus for preheating a target deposition area on a substrate and a laser powder blowing system for heating and melting metal onto the target deposition area on the substrate.

Fig. 9 is a schematic side view of an embodiment of a dual torch system provided herein that includes an electron beam device for preheating a target deposition area on a substrate and a laser device for heating and melting a wire onto the target deposition area on the substrate.

Fig. 10 is a schematic side view of an embodiment of a dual torch system provided herein that includes a laser device for preheating a target deposition area on a substrate and an electron beam device for heating and melting a wire onto the target deposition area on the substrate.

Fig. 11 is a schematic side view of an embodiment of a dual torch system provided herein that includes a first electron beam device for preheating a target deposition area on a substrate and a second electron beam device for heating and melting a wire onto the target deposition area on the substrate.

Detailed Description

A. Definition of

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents, patent applications, published applications and publications, websites and other published materials referred to throughout the disclosure herein are incorporated by reference in their entirety unless otherwise indicated. If there are multiple definitions for a term herein, the definition in this section controls. It will be appreciated that where a URL or other such identifier or address is referenced, such identifier may change and particular information on the internet may come, but equivalent information may be found by searching the internet. The references demonstrate the availability and public dissemination of such information.

As used herein, the singular forms "a", "an" and "the" include the plural forms as well, unless the context clearly indicates otherwise.

As used herein, ranges and amounts can be expressed as "about" a particular value or range. "about" also includes the exact amount. Thus, "about 5%" means "about 5%" and also means "5%". "about" means within the error range of typical experiments for the application or intended purpose.

As used herein, the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, but these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

As used herein, "optional" or "optionally" means that the subsequently described event or circumstance occurs or does not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, an optional component in a system means that the component may or may not be present in the system.

As used herein, "combination" refers to any association between two items or between more than two items. The association may be spatial or refer to the use of two or more items for a common purpose.

As used herein, "plasma arc torch" or "PAW torch" refers to a torch that may be used for plasma arc welding. The torch is designed so that the gas can be heated to a high temperature to form a plasma and become conductive, the plasma then transfers the arc to the workpiece, and the intense heat of the arc can melt the metal and/or fuse the two metal pieces together. The PAW torch may include a nozzle for constricting the arc, thereby increasing the power density of the arc. The plasma gas is typically argon. A plasma gas may be supplied along the electrodes and ionized and accelerated near the cathode. The arc may be directed toward the workpiece and is more stable than a free-burn arc (such as in a TIG torch). The PAW torch also typically has an outer nozzle for providing shielding gas. The shielding gas may be argon, helium, or a combination thereof, and helps to minimize oxidation of the molten metal. In a PAW torch, the current may typically be up to about 400A, and the voltage may typically be between about 25V to 35V (but may be up to about 14 kW). The present invention does not relate to any particular option or type of PAW torch. Any known or conceivable device capable of functioning as a PTA torch may be used. An exemplary PAW torch is a Plasma Transferred Arc (PTA) torch.

The term "plasma transferred arc torch" or "PTA torch" used interchangeably herein refers to any device capable of heating and exciting a stream of inert gas into a plasma by an arc discharge and then transferring the stream of plasma gas including the arc through an orifice (such as a nozzle) to form a constricted plume that extends out of the orifice and transfers the intense heat of the arc to a target region. The electrode and the target area may be electrically connected to a dc power supply such that the electrode of the PTA torch becomes a cathode and the target area becomes an anode. This will ensure that the plasma plume including the arc delivers a highly concentrated heat flux to a small surface area of the target area while at the same time providing excellent control over the area extension and magnitude of the heat flux supplied from the PTA torch. Plasma transferred arcs have the advantage of providing a stable and consistent arc with little drift and good tolerance to length deviations between the cathode and anode. Thus, the PTA torch is suitable for both preheating the surface and, in some applications where a preheated region or melt pool is formed in the substrate, heating and melting the wire feed. The PTA torch may advantageously have an electrode made of tungsten and a nozzle made of copper. However, the present invention is not directed to any particular option or type of PTA torch. Any known or conceivable device capable of functioning as a PTA torch may be used.

The term "power density" as used herein refers to the amount of power distributed from a laser beam or electron beam to a unit area.

As used herein, "SFFF" refers to solid freeform fabrication.

The term "metallic material" as used herein refers to any known or conceivable metal or metal alloy that can be formed into a wire and used in a solid freeform fabrication process to form a three-dimensional object. Examples of suitable materials include, but are not limited to, titanium and titanium alloys, such as, for example, Ti-6Al-4V alloy.

The term "similar metallic material" as used herein means that the metallic material has the same metal or metal alloy as the reference metallic material.

The term "holding substrate" as used herein refers to a target substrate on which additional material, the same or different from the holding substrate, is deposited to form a workpiece using SFFF or solid freeform fabrication techniques. In an exemplary embodiment, the holding substrate is a flat plate. In an alternative embodiment, the retention substrate may be a forged component. In an alternative embodiment, the holding substrate may be the object on which the additional material is to be deposited. In an exemplary embodiment, the holding substrate may become a part of the workpiece. The material for holding the substrate may be a metal or a metal alloy. In an exemplary embodiment, the holding substrate is made of the same metal as the wire feed material.

The term "substrate" as used herein refers to a target material for receiving molten metallic material to form a three-dimensional object. The base material will be the holding substrate when the first metallic material layer is deposited. When one or more layers of metallic material are deposited on the holding substrate, the base material will be the upper layer of the deposited metallic material, which will deposit a new layer of metallic material. As used herein, the term "workpiece" refers to a metal body produced using solid freeform fabrication.

The terms "computer-aided design model" or "CAD model" used interchangeably herein refer to any known or conceivable virtual three-dimensional representation of an object to be formed, which may be used in the control system of the device according to the second aspect of the invention: the position and movement of the holding base plate are adjusted and the welding torch is operated with the integrated wire feeder such that the physical object is built by fusing successive deposits of metallic material onto the holding base plate in a pattern that causes the physical object to be built according to the virtual three-dimensional model of the object. This may be obtained, for example, by forming a virtual vectorized layered model of the three-dimensional model by first dividing the virtual three-dimensional model into a set of virtual parallel layers and then dividing each parallel layer into a set of virtual quasi-one-dimensional artifacts. A physical object may then be formed by the joining control system to deposit and fuse a series of quasi-one-dimensional pieces of metallic material onto the support substrate according to the pattern of the first layer of the virtual vectorized layered model of the object. The sequence of second layers of the object is then repeated by depositing and fusing a series of quasi-one-dimensional weldable material pieces onto the previously deposited layers in a pattern according to the second layers of the virtual vectorized layered model of the object. Repeating the successive layer-by-layer deposition and fusion processes for each successive layer of the virtual vectorized layered model of the object until the entire object is formed. However, the invention is not related to any specific CAD model and/or computer software for running the control system of the device according to the invention, nor is the invention related to any specific type of control system. Any known or conceivable control system (CAD model, Computer Aided Manufacturing (CAM) system or software, computer hardware and actuators, etc.) capable of building a metallic three-dimensional object by solid freeform fabrication may be used, provided that the control system is adapted to operate one first PTA torch to form a pre-heat zone or melt pool and to operate a second PTA torch to melt a feed wire of metallic material into the melt pool, respectively.

B. Double-welding gun system

It has been determined that the deposition rate of molten metal onto a formed workpiece can be increased using a dual torch system in which a first torch preheats the substrate to form a preheated region and a second torch is used to heat and melt the metal onto the preheated region of the substrate. As used herein, the term "welding gun" or simply "gun" is used interchangeably and means any heating device or device capable of generating heat or a source of heat. Non-limiting examples of welding guns or guns include a PAW welding torch (including PTA torches), a laser emitting device ("laser device"), and an electron beam emitting device ("electron beam device"). The first gun may ensure fusion between the substrate or workpiece and the molten metal produced by the second gun acting on the metal, such as a wire or metal powder. The first gun may deepen the melting of the molten metal into the preheating zone of the substrate. Superheating from the molten metal droplets may maintain a molten pool near the pre-heating region of the substrate. Preheating of the substrate can result in better wetting, better deposition profile, and increased deposition rate. With respect to the deposition profile, by preheating the substrate, a more rounded and wider deposition profile can be obtained. The improved profile may result in a profile having a favorable angle toward the substrate, which may promote fusion with the substrate and prior metal deposition. The improved fusing results in a finished product with improved integrity.

Each welding torch comprises a heating device. Each torch may be individually controlled and each torch may be adjusted to produce individual temperature effects. The advantage of such an apparatus is that the amount of thermal energy applied to the metal feedstock to be melted onto the pre-heating zone of the substrate can be greater than the amount of thermal energy applied to the substrate, thereby avoiding overheating of the substrate.

In exemplary embodiments, one heating device used as a torch may be used to preheat the substrate and optionally form the molten pool, while another heating device used as another torch may be used alone to melt the wire or consumable electrode. In an alternative embodiment, a heating device used as a torch to melt the wire or consumable electrode may also be used to further heat the substrate at the location where molten metal melted from the wire or consumable electrode is to be deposited. Additional heating of the already preheated region or even the molten bath may allow for better temperature control of the region where metal is to be deposited, thereby further achieving the benefit of having a preheated region or molten bath.

In an exemplary embodiment, the heating device of the torch used as the fusion wire or consumable electrode may be a PAW torch (e.g., PTA torch), wherein the torch is also connected to the same dc power supply as the substrate. Thus, while being used to melt the wire, the torch may also be turned to the cathode while the substrate is turned to the anode, thereby transferring a pulsed heat flux to an area of the substrate in an area that has been preheated by another heating device or gun and on which the wire is melted and thus metal is deposited.

Similarly, other types of heating devices or guns may be used to achieve this additional heating of the pre-heating region or melt pool in the substrate. For example, when a laser device is used as a welding gun to melt the wire, the laser may be directed to the wire and substrate rather than just to the wire. Any known means for redirecting the laser may be used to direct the laser or the separation laser and direct it to the substrate while still melting the wire. In an exemplary embodiment, one or more mirrors may be used to separate or reflect at least a portion of the laser light such that the laser light impinges the wire and substrate rather than just the wire. The use of an electron beam device as a welding gun can also be used for this purpose. For example, an electron beam may be directed toward the wire to melt the wire and also toward the substrate to provide additional heat to the pre-heat zone or melt pool. Any known method of directing an electron beam may be used.

Positioning of the substrate and any one or more of the torches may be accomplished using one or more actuators. In an exemplary embodiment, the substrate may be repositioned or moved using an actuator tray on which the substrate rests. The actuator tray can move the substrate in any direction. In exemplary embodiments, the actuator tray may be disposed on a rail system or a rail system and may be capable of moving the substrate in any desired direction. Alternatively, the actuator tray may be operated using a robot arm or a robotic arm. The actuators may also be operated using a hydraulic system. Similarly, one or more actuators may be used to move one or more welding guns. For example, each of the one or more welding guns may be attached to an independently controlled actuator arm, such as a robotic arm or a robotic arm. The actuators may also be operated using a hydraulic system. It is also possible to implement using other types of mechanisms for the actuator arm, such as a rail system or a track system. In an exemplary embodiment using two or more torches, each torch may be moved independently. In an alternative embodiment using two or more welding guns, the positions of the two or more welding guns may be fixed relative to each other and the one or more actuator arms move the two or more welding guns simultaneously. In an exemplary embodiment, the actuator tray is the only actuator used that holds one or more welding guns in a fixed position during deposition. In an alternative embodiment, the actuator tray moves the substrate in only two directions in one plane, while the one or more actuator arms move the one or more torches in only one direction (e.g., perpendicular to the plane in which the actuator tray moves). The opposite is true, where one or more actuator arms move one or more torches in two directions in a plane, while an actuator tray moves the substrate in a single direction. In an alternative embodiment, the substrate is held in a fixed position during deposition and one or more actuator arms are used to move one or more torches. In yet another alternative embodiment, both the actuator tray and one or more actuator arms are used to move the substrate and one or more torches.

A control system, including, for example, a Computer Aided Manufacturing (CAM) system or software, may be used to operate and regulate engagement of one or more actuators that may constantly position and move any one or a combination of the substrate, one or more welding torches such that the preheat region or weld puddle is located at a predetermined deposition region given by the CAD model of the object to be formed.

The control system may include a computer processor or Central Processing Unit (CPU), a CPU display, one or more power supplies, power connectors, signal modules as inputs and/or outputs, integrated shielding of analog signals, storage devices, circuit boards, memory chips or other storage media, non-transitory computer-readable storage media having computer-readable programs embodied therein, or any combination thereof. The computer readable program may contain suitable software for partially or fully automating any one or combination of the systems. The computer readable program may contain suitable software for monitoring and/or adjusting parameters such as temperature, pressure, workpiece position, deposition rate, or any combination thereof. Exemplary control systems include, but are not limited to, SIMATIC-S7-1500 from Siemens ag (Munich, Germany), the IndraMotion MTX system available from Posth-Leag (Mei-Hepan, Germany), and the SIGMATEK C-IPC compact industrial computer system available from SIGMITEK ag & Bigeneration (Pythitzhason, Austria).

It is noted that although the embodiments described herein are shown according to the illustrative examples in fig. 3-11, where both torches are located on the same side of the substrate, the invention is not limited thereto. In an exemplary embodiment, the welding torch used to achieve the pre-heated area in the substrate may instead be located on the opposite side of the substrate from the welding torch used to melt the wire.

System comprising two PTA torches

In an exemplary embodiment, the present invention relates to a method of manufacturing a three-dimensional object of metallic material by solid freeform fabrication, wherein the object is made by fusing together successive deposits of metallic material on a holding substrate, the method being characterized by comprising:

using a holding substrate made of a metal material similar to the object to be made, and

-each successive deposit is obtained by:

i) using a first Plasma Transferred Arc (PTA) to preheat and optionally form a molten pool in the substrate at a location where the metallic material is to be deposited,

ii) feeding the metallic material to be deposited in the form of a wire to a position above the preheating zone or bath,

iii) heating and melting the wire using a second Plasma Transferred Arc (PTA) such that the molten metallic material is dripped onto the pre-heating zone or molten pool, and iv) moving the position of the holding substrate relative to the first and second PTAs in a predetermined pattern such that the continuous deposit of molten metallic material solidifies and forms a three-dimensional object. In a second aspect, the present invention relates to an apparatus for manufacturing a three-dimensional object of metallic material by solid freeform fabrication, wherein the apparatus comprises:

a welding torch having an integrated wire feeder feeding a wire of metallic material,

-an actuator tray for moving the substrate relative to at least the first heating means, or an actuator arm for moving the second heating means, or any combination of these actuators, and

a control system capable of reading a Computer Aided Design (CAD) model of the object to be formed and using the CAD model to adjust the position and movement of the system for positioning and moving the holding baseplate, and operating the welding torch with the integrated wire feeder such that the physical object is built by fusing successive deposits of metallic material onto the holding baseplate, characterized in that,

the holding substrate is made of a metal material similar to the object to be made,

-the welding torch comprises:

i) a first Plasma Transferred Arc (PTA) torch electrically connected to the substrate, an

ii) a second Plasma Transferred Arc (PTA) torch electrically connected to a supply wire of metallic material,

-the control system is capable of operating and adjusting the first PTA torch individually to form and maintain a pre-heating zone or a melt pool in the substrate at the location where the metallic material is to be deposited, and

the control system is capable of operating and adjusting the wire feeder and the second PTA torch individually to melt the supplied metallic material at a location such that molten metallic material drips onto the preheating zone or the melt pool.

Using a separately controlled first PTA torch to preheat the substrate or form the molten bath and a separate second PTA torch to melt the feed wire of the metallic material provides the advantage of being able to increase the heat supplied to the feeder of wires regardless of the heat supplied to the substrate, so that the heat flux into the feed material can be increased without the risk of forming a "spray arc" that creates spatter. Thus, the deposition rate of the molten metal feed can be increased without simultaneously overheating the substrate, and without the risk of splashing or forming excessive pre-heat zones or pools and thus loosely controlling consolidation of the deposited material. This feature is obtained by connecting a direct current power supply such that the electrode of the first PTA torch becomes negative polarity and the substrate becomes positive polarity to define a circuit for transferring charge by arc discharge between the electrode of the first PTA torch and the substrate, and by connecting the electrode of the second PTA torch to the negative electrode of the direct current power supply and connecting a supply wire of metallic material to the positive electrode to form a circuit for transferring charge by arc discharge between the electrode of the second PTA torch and the supply wire of metallic material.

The first PTA torch and the second PTA torch can advantageously have separate power supplies and means for regulating the power supplied to the respective torches. The means for adjusting the power may advantageously comprise means for monitoring the temperature of the deposition area of the substrate and means for adjusting the width and positioning of the arc, such as magnetic arc deflection means. Furthermore, the first PTA torch used to preheat the substrate and optionally form a puddle in the substrate can advantageously form a wide arc, such as by a gas tungsten arc torch (GTAW torch, also denoted as TIG torch in the literature) to simply preheat or form a puddle in a wider region of the substrate surface.

The feed rate (wire speed) and positioning of the feed wire of metallic material may be controlled and adjusted as a function of the effect of the power supplied to the second PTA torch to ensure that the wire is continuously heated and melted when it reaches a pre-heating region in the substrate or a predetermined position above the molten bath. This can be achieved by using a conventional gas metal arc torch (GMAW torch, also known as MIG torch) as a wire feeder without forming an arc in the MIG torch. This embodiment of the wire feeder has the advantage of being able to electrically connect the wire to the dc power supply of the second PTA torch and also position the wire very accurately. The supply wire of metallic material may have any practically realizable size, such as 1.0mm, 1.6mm, 2.4mm, etc.

The effectiveness of the supply to the first PTA torch and the second PTA torch will depend on the metal material applied, the diameter of the feed wire, the heat resistance of the substrate, the deposition rate, etc. Thus, the present invention is not dependent on any particular power window, but may apply any practical functional potential difference and current that results in functional operation of the first PTA torch and the second PTA torch. The skilled person will be able to find these parameters by trial and error tests. Experiments conducted by the applicant have shown that by using a 1.6mm diameter wire made of a grade 5 titanium alloy, a three-dimensional object with similar mechanical properties to a conventional titanium object can be manufactured at a deposition rate of 3.7 to 3.8kg/h when supplying about 150A for the first PTA torch and about 250A for the second PTA torch. It is believed that deposition rates of up to 10kg/h can be achieved by performing SFFF deposition according to the first and second aspects of the invention in an effectively protected atmosphere, such as the reaction chamber disclosed in WO 2011/0198287. Another experiment conducted by the applicant confirmed this, where the wire diameter was 2.4mm, grade 5 titanium, and the deposition rate was 9.7kg/h when the first PTA torch was supplied with a current of about 250A and the second PTA torch was supplied with a current of about 300A.

Alternatively, the invention may also include means for generating a heat pulse in the pre-heating zone or the molten bath in order to break up the growth tendency of the crystalline dendrites at that location. This feature allows the formation of metal objects with enhanced mechanical properties due to the improved grain structure. The heat pulse may be obtained by using a third dc generator that delivers a pulsed dc potential and connects the negative pole of the dc generator to the electrode of the second PTA torch and the positive pole to the substrate to form an electrical circuit that transfers charge by a pulsed arc discharge between the electrode of the second PTA torch and the substrate. The arc discharge between the electrode of the second PTA torch and the substrate will turn on and off according to the applied pulsed dc potential and thereby create a pulsed heat flux into the pre-heating zone or molten pool in the substrate. The frequency of the pulses may be in the range of 1Hz up to several kHz or more, i.e. 10 kHz.

A first exemplary embodiment of a device according to the second aspect of the present invention is schematically illustrated in fig. 3. The figure shows a holding substrate 1 made of a Ti-6Al-4V alloy in the shape of a rectangular cuboid, on which holding substrate 1 a three-dimensional object made of the same Ti-6Al-4V alloy is to be formed by solid freeform fabrication. The figure shows the initial part of the deposition process in which a first electrode 2 of Ti-6Al-4V alloy is being deposited.

The wire 3 made of Ti-6Al-4V alloy is continuously supplied by a wire feeder 4 which positions the wire 3 so that its distal end is above a preheating zone or melt pool 5 at a deposition zone on the holding substrate 1. The wire 3 is given a speed indicated by the upper arrow in the figure, which corresponds to the heating and melting rate of the distal end, so that a droplet 6 of molten wire is continuously supplied to the preheating zone or molten pool 5.

The first plasma transferred arc 7 is formed by a PTA torch 8 which is electrically connected to a dc power supply 9 such that the electrode 10 of the PTA torch becomes the cathode and the retaining substrate 1 becomes the anode. The plasma transferred arc 7 is continuous and directed to heat and optionally melt the substrate at the deposition area (the substrate is the holding substrate at this stage of the SFFF process) so that a pre-heating zone or melt pool 5 is obtained. The effect of the dc power supply 9 is adjusted to maintain a preheating zone or bath 5 of constant size and extent by a control system (not shown). The PTA torch 8 is a Gas Tungsten Arc Welding (GTAW) torch equipped with a magnetic arc deflector (not shown) to control the size and position of the arc 8. The second plasma transferred arc 11 is formed by a PTA torch 12 electrically connected to a dc power supply 13 such that electrode 14 of the PTA torch 12 becomes the cathode and the feed wire 3 becomes the anode. The plasma transferred arc 11 is continuous and directed to heat and melt the distal end of the wire 3. The effect of the dc power supply 13 is adjusted to maintain the heating and melting rates in accordance with the feed rate of the wire so that the formation of the droplets 6 is timed to maintain a continuous drop of molten wire onto the pre-heating zone or molten bath 5. The effect supplied by the dc power supply 13 and the feed rate of the wire 3 out of the wire feeder 4 are constantly regulated and controlled by the control system so that molten wire is supplied to the preheating zone or molten bath 5 at a rate that provides a predetermined deposition rate of Ti-6Al-4V alloy. The control system engages simultaneously to operate and adjust the engagement of actuators (not shown) which constantly position and move the holding substrate 1 so that the pre-heating zone or melt pool is located at a predetermined deposition point given by the CAD model of the object to be formed. At this stage of the SFFF process, the holding substrate 1 is moved as indicated by the arrow below.

A second exemplary embodiment of the invention is the first exemplary embodiment given above comprising additional means for forming a heat pulse in the preheating zone or melt pool 5. The means for forming the thermal pulse is a dc power supply 15 that is electrically connected to the second PTA torch 12 so that the electrode 14 becomes the cathode and the holding substrate 1 becomes the anode. In addition, there is a device 16 for pulsing the power delivered by the direct current power supply 15, so that the arc 11, in addition to heating and melting the wire 3, also enters the preheating zone or the melt pool 5 at the same frequency as the pulsed power supply and thus delivers a pulsed heat flux to the melt pool. The device 16 may be regulated by a control system and provides pulsed arc discharges into the preheat zone or the melt pool at a frequency of 1 kHz.

System comprising a laser device and a PAW torch

In an alternative embodiment of the dual torch system provided herein, the system may include a laser device as a heating device for the torch and a PAW torch, such as a PTA torch, as a heating device for the other torch. In some configurations, a laser apparatus preheats a target deposition area on a substrate to form a preheated area, and a PAW torch heats and melts a wire, producing a molten metal droplet that falls into the preheated area of the target deposition area. In some configurations, the PAW torch preheats a target deposition area on the substrate to form a preheated area, and the laser device heats and melts the wire, producing a droplet of molten metal that falls into the preheated area of the target deposition area.

In a first configuration, the laser device may be arranged to direct laser energy to a target area of the substrate to form a pre-heat zone, and the PAW torch may be arranged to direct a plasma transferred arc onto an end of the wire located above the pre-heat zone of the substrate. The thermal energy of the PAW torch melts the tip of the wire, forming a molten metal droplet of wire that falls onto a pre-heated region of the substrate below the wire tip. The laser device may promote fusion between the substrate and the molten metal material deposited thereon by deepening the melting of the molten metal droplets into the substrate. The arc of the PAW torch may also contribute thermal energy near the pre-heating region of the target deposition area, thereby contributing to the thermal energy provided by the laser beam. For example, a PAW torch may be connected to the same dc power supply as the substrate, thereby becoming the cathode, while the substrate becomes the anode, and thereby delivering a pulsed heat flux to the substrate. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may include a wire supply to supply wire. The wire supply may be positioned between the laser and the PAW torch or may be positioned such that it is closer to the PAW torch than the laser.

The system can also include a positioning device that can position the wire over a pre-heat region formed in the substrate by the laser. The positioning device can also suitably place the end of the wire in a plasma transferred arc, suitably melt it and cause the droplets formed by said plasma transferred arc melting to fall onto the pre-heated area of the substrate underneath it.

The wire may be or contain aluminum, chromium, copper, iron, hafnium, tin, manganese, molybdenum, nickel, niobium, silicon, tantalum, titanium, vanadium, tungsten or zirconium or composites or alloys thereof. In some embodiments, the wire comprises titanium or a titanium alloy. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. When the wire is in the form of a wire, the wire may have a cross-section of any desired shape. A typical cross-section is a circular cross-section. The wire diameter may be up to about 10mm, and may range from about 0.8mm to about 5 mm. The wire may be of any practical realizable size, e.g., 1.0mm, 1.6mm, 2.4mm, etc. The feed rate and positioning of the wire can be controlled and adjusted based on the effect of the power supply to the torch to ensure that the wire is continuously heated and melted as it reaches a predetermined location above the pre-heat zone or molten pool in the substrate.

The laser device can generate a laser beam of sufficient energy to transfer thermal energy to the substrate to preheat a region of the substrate. Preheating the substrate via energy from the laser beam promotes radicals by deepening melting in the substrateFusion between the material and the molten metal material. In some embodiments, at least a portion of the substrate may be melted by the energy of the laser beam from the laser device. In some embodiments, the laser beam of the laser apparatus applies sufficient heat to form a pre-heated region or melt pool in the substrate at the location where the metallic material is to be deposited. Examples of suitable laser devices may include ytterbium (Yb) lasers, Yb fiber-coupled diode lasers, Yb: glass lasers, diode-pumped Yb: YAG lasers, neodymium-doped ytterbium aluminum garnet (Nd: YAG) lasers, CO lasers, and the like₂Lasers, CO lasers, Nd: glass lasers, neodymium-doped ytterbium orthovanadate (Nd: YVO) lasers, Cr: ruby lasers, diode-pumped lasers, excimer lasers, gas lasers, semiconductor lasers, solid-state lasers, dye lasers, X-ray lasers, free electron lasers, ion lasers, gas mixture lasers, chemical lasers and combinations thereof. Preferred lasers include Yb lasers, particularly Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers may be less reflective than other laser wavelengths.

The PAW torch may be any configuration capable of generating an arc to heat and melt the wire, such as a PTA torch, Gas Metal Arc Welding (GMAW), in particular using an inert gas to generate the arc (metal inert gas welding or MIG welding). The wire is melted in a plasma generated by a torch using an electric arc and the melted wire is deposited on a pre-heated area or molten pool on the workpiece to add and form a near net-shape metal body.

Titanium metal or titanium alloys heated to above 400 c may oxidize when contacted with oxygen. Accordingly, there is a need to protect welds and heated objects formed by layered manufacturing from oxygen in the ambient atmosphere. One solution to this problem is to enclose the deposition system within a chamber that is closed to the ambient atmosphere and can be made substantially oxygen free. An exemplary chamber is described in international patent application publication WO2011/019287 (Guldberg). Weld purge chambers for welding under inert gas are also commercially available (e.g., Soltzbury LC technology solutions, Mass.) and can be easily designed or engineered to accommodate systems of any size or configuration. By using a deposition chamber that is substantially oxygen free, such as argon or other inert gas instead of ambient gas, the speed of the welding process may be increased, as the welding zone may be allowed to reach higher temperatures without risk of excessive oxidation of the weld. For example, in the production of objects of titanium or titanium alloys, it is no longer necessary to cool the weld zone below 400 ℃ to avoid oxidation.

In an alternative configuration that does not use a deposition chamber without oxygen, the dual torch system may use a shielding gas instead of a chamber to avoid oxidation. In such a system, a nozzle directs a shielding gas (such as Ar) to the area around the wire and PTA torch. For example, an inert gas may be directed through a nozzle disposed about an electrode of the torch. The nozzle may direct an inert gas proximate the molten weld pool. The gas isolates the preheat zone or bath from the atmosphere to prevent oxidation. In Ireland et al (U.S. patent No. 7,220,935); comon et al (U.S. Pat. No. 9,145,832); and Cooper et al (U.S. patent application publication No. US 2010/0276396).

An exemplary embodiment of one configuration is shown in fig. 9, where a laser apparatus preheats a target deposition area on the substrate to form a preheated area, and a PTA torch heats and melts the wire. In the illustrated embodiment, a substrate 200 shaped as a rectangular cuboid is produced from SFFF. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 9 includes: a laser device 410 positioned such that a laser beam 420 generated by the optical device is directed to a target area to preheat the substrate 200 at the target area; and a PTA torch 110 positioned above the target area to melt the wire to form a molten metal droplet that falls into the preheating zone 210.

A wire 150 made of a material that forms a workpiece with SFFF is continuously supplied to the plasma transferred arc 130 generated by the PTA torch 110. The wire 150 is supplied by the wire feeder 140 and is positioned such that the end of the wire 150 is located above a preheating zone or melt pool 210 at a deposition zone on the substrate 200. The wire 150 may be given a velocity (as indicated by arrow 170) towards the plasma transferred arc 130. The speed of the wire 150 may be selected such that the heating and melting rate of the distal end of the wire 150 is such that the molten metal droplets 160 of the molten wire 150 are continuously supplied to the pre-heat zone or molten pool 210. The wire 150 may be fed into the plasma transferred arc 130 generated by the PTA torch 110 at any angle and is not limited to the angle shown in fig. 9.

The plasma transferred arc 130 is formed by the PTA torch 110. As shown, the PTA torch 110 is electrically connected to the power supply 310 such that the torch electrode 120 becomes a cathode and the wire 150 becomes an anode. The power supply may be an ac power supply or a dc power supply. The plasma transferred arc 130 is continuous and directed to heat and melt the distal end of the wire 150. The effect of the dc power supply 310 is adjusted to maintain the heating and melting rates in accordance with the feed rate of the wire 150 so that the formation of the molten metal droplets 160 is timed to maintain a continuous drop of molten wire into the pre-heating zone or molten pool 210. The effect supplied by the dc power source 310 and the feed rate of the wire 150 out of the wire feeder 140 are constantly adjusted and controlled by the control system so that molten wire 150 is supplied to the preheating zone or molten pool 210 at a rate that provides a predetermined deposition rate of metal or metal alloy onto the substrate 200. The control system may be engaged simultaneously to operate and adjust the engagement of actuators (not shown) that constantly position and move the substrate 200 so that the preheat region or melt pool 210 is located at a predetermined deposition point given by the CAD model of the object to be formed. At this stage of the SFFF process, the substrate 200 is moved as indicated by arrow 240.

Fig. 9 also depicts an alternative electrical configuration that may generate a heat pulse in the preheat region or melt pool 210. In the illustrated embodiment, the dc power supply 320 is electrically connected to the PTA torch 110 such that the torch electrode 120 becomes a cathode and the substrate 200 becomes an anode. In addition, a pulse frequency generator 330 for pulsing the power delivered by the dc power source 330 is positioned in the circuit so that the plasma transferred arc 130 will enter the preheat zone or melt pool 210 at the same frequency as the pulsed power source in addition to heating and melting the wire 150 and thus deliver a pulsed heat flux to the preheat zone or melt pool 210. The pulse frequency generator 330 may be regulated by the control system. In some embodiments, an alternative electrical configuration provides pulsed arc discharge into the preheat zone or melt pool 210 at a frequency of 1 to about 200Hz, although frequencies up to about 1kHz may be used. Both power supplies 310 and 320 may be pulsed, or only one power supply 310 or 320 may be pulsed. For example, the wire melting current may be pulsed, or the current to the workpiece may be pulsed, or the wire melting current and the current to the workpiece may be pulsed. When both power supplies 310 and 320 are pulsed, the pulse frequencies may be the same or different. The pulse frequency can be individually chosen up to 1 kHz. The pulse frequency may be individually selected in the range of about 1 to 200Hz or in the range of about 1 to 100Hz or in the range of about 10 to 100Hz or in the range of about 5 to 50 Hz.

Using a laser device to preheat the substrate and form the preheating zone and using the PTA torch to melt the feed wire of the metallic material provides the advantages of: the heat supplied to the supply of wire can be increased independently of the heat supplied to the substrate, so that the heat flux into the supply material can be increased without the risk of forming a "spray arc" that generates spatter. The melting power applied to the wire may be selected to match the mass input (amount of molten metal droplets to be added to the wire of the workpiece) to ensure stable melting and/or burnout of the wire. The laser device may allow for the directed placement of thermal energy to the target area. Thus, the deposition rate of the molten metal feed can be increased without simultaneously overheating the substrate, and without the risk of splashing or forming excessive pre-heat zones or pools and thus losing control over consolidation of the deposited material.

The laser device may also be configured such that the laser beam may be scanned in the X or Y direction to cover an area only wider than the focal point of the laser beam. The scan interval may be about 0.001 to about 0.1 inches. The melting behavior of the target region heated by the laser device can be changed by adjusting the laser beam. For example, the power of the laser beam may be adjusted, or the laser beam apparatus may be configured such that the laser beam may be moved relative to the workpiece surface, or the approach direction and angle of the laser beam may be adjusted, or any combination of these may be modified to adjust the preheating of the target area. Any loss of efficiency due to reflection of the laser beam by the workpiece surface can also be compensated for by adjusting the approach direction and angle of the laser beam.

By moving the laser beam along a predetermined path relative to the workpiece surface, the area heated by the laser beam layer can be defined in two dimensions on the substrate, the width of the layer being determined by the diameter at which the laser beam impinges on the substrate. The movement of the laser beam along the predetermined path may be under computer control. Adjusting the pulse shape and/or duration provides a way to control the specific power of the laser provided during the movement of the laser beam. The laser beam may also be delivered in pulses. Conventional focusing optics may also be used to adjust the focus of the laser beam on the surface of the workpiece.

The laser device 410 may be mounted to be movable under computer control in an X-Y plane parallel to the substrate surface and vertically in a Z direction orthogonal thereto. Thus, the laser beam 420 may be directed to any point in the X-Y plane and directed vertically to accommodate workpieces of different heights and regions of different heights within the workpiece. As shown in fig. 9, the lateral direction is the direction of arrow 240, and the apparatus is in the process of manufacturing layer 220. When using a laser device as a torch to form the pre-heat zone or melt pool, mirrors may also be used to direct the laser to define the area on the substrate for pre-heating or melting.

In various configurations, the PAW torch can be arranged to direct a plasma transferred arc to a target area of the substrate to form a pre-heat zone, and the laser device can be positioned to direct a laser beam onto an end of the wire located above the substrate pre-heat zone. The thermal energy of the laser beam melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. The PAW torch preheats the target area and may promote fusion between the substrate and the molten metal material by deepening the molten metal droplet to melt into the substrate. The laser beam of the laser apparatus may also be used to contribute thermal energy in a pre-heated region or melt pool in the substrate at the target deposition area, thereby contributing to the thermal energy provided by the PAW torch. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may comprise a wire supply for supplying a wire to a desired position under the laser beam. The wire supply may be positioned between the laser and the PAW torch or it may be positioned such that it is closer to the laser device than the PAW torch.

The system can also include a positioning device that can position the wire over a pre-heating region formed in the substrate by the PAW torch. The positioning device may also suitably place the end of the wire in the laser beam so that the wire is suitably melted and so that a droplet of molten metal formed by melting the wire falls onto the preheated area of the substrate therebelow.

The wire may be or contain aluminum, chromium, copper, iron, hafnium, tin, manganese, molybdenum, nickel, niobium, silicon, tantalum, titanium, vanadium, tungsten or zirconium or composites or alloys thereof. In some embodiments, the wire comprises titanium or a titanium alloy. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. The wires may be of any configuration and have a cross-section of any desired shape. The wire may have a circular cross-section. The diameter of the wire may be in the range of about 0.8mm to about 5 mm. The wire may have any practically realizable cross-sectional dimension, such as 1.0mm, 1.6mm, 2.4mm, etc. The feed rate and positioning of the wire can be computer controlled to ensure that the wire melts when it reaches a predetermined position above the pre-heat zone or melt pool in the substrate.

The laser device may generate a laser beam of sufficient energy to transfer thermal energy to the wire to melt the wire to form a molten metal droplet. Examples of suitable laser devices may include ytterbium (Yb) lasers, Yb fiber-coupled diode lasers, Yb: glass lasers, diode-pumped Yb: YAG lasers, neodymium-doped ytterbium aluminum garnet (Nd: YAG) lasers, CO2 lasers, CO lasers, Nd: glass lasers, neodymium-doped ytterbium orthovanadate (Nd: YVO) lasers, Cr: ruby lasers, diode-pumped lasers, excimer lasers, gas lasers, semiconductor lasers, solid state lasers, dye lasers, X-ray lasers, free electron lasers, ion lasers, gas mixture lasers, chemical lasers, and combinations thereof. Preferred lasers include Yb lasers, particularly Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers may be less reflective than other laser wavelengths.

The PAW torch used to preheat the target area of the workpiece may be of any configuration capable of generating an arc to heat at least a portion of the workpiece surface and enable it to accept a droplet of molten metal from the molten wire. Exemplary PAW torches may include PTA torches or torches for Gas Metal Arc Welding (GMAW), particularly using an inert gas to generate an arc (metal inert gas welding or MIG welding). The target area of the workpiece is preheated by the torch using the arc generated plasma. The molten wire is deposited as a molten metal droplet into a pre-heated zone or puddle on the workpiece to add and form a near net-shape workpiece.

When a PAW torch is used (such as a PTA torch), the arc of the plasma transferred arc can be controlled to define a region of preheating or melting. The magnetic field may be used to regulate the arc. Moreover, the area in the substrate to be preheated or melted may also be defined by moving the PAW torch using mechanical and/or hydraulic actuators or any of the actuators as described herein.

As mentioned above, titanium metal or titanium alloys heated to above 400 ℃ may oxidize when contacted with oxygen. In order to protect the weld seam formed by layered manufacturing and the heated object from oxygen in the ambient atmosphere, a chamber may be used that is closed to the ambient atmosphere and may be made substantially oxygen-free. An exemplary chamber is described in international patent application publication WO2011/019287 (Guldberg). Weld purge chambers for welding under inert gas are also commercially available (e.g., Soltzbury LC technology solutions, Mass.) and can be easily designed or engineered to accommodate systems of any size or configuration. By using a deposition chamber that is substantially oxygen free, such as argon or other inert gas instead of ambient gas, the speed of the welding process may be increased, as the welding zone may be allowed to reach higher temperatures without risk of excessive oxidation of the weld.

Alternatively, the dual spray gun system may use a shielding gas instead of a chamber to avoid oxidation. In such a system, the nozzle directs a shielding gas (such as Ar) to the target area and the area around the PTA torch. For example, an inert gas may be directed through a nozzle disposed about an electrode of the torch. The nozzle may direct an inert gas to the target area and adjacent the molten weld pool. The gas isolates the preheat zone or bath from the atmosphere to prevent oxidation. In Ireland et al (U.S. patent No. 7,220,935); comon et al (U.S. Pat. No. 9,145,832); and Cooper et al (U.S. patent application publication No. US 2010/0276396).

An exemplary embodiment of one configuration is shown in fig. 10, in which a PTA torch preheats a target deposition area on a substrate to form a preheated area, and a laser beam from a laser device heats and melts a wire. In the illustrated embodiment, a substrate 200 shaped as a rectangular cuboid is produced from SFFF. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 10 includes: a PTA torch 110 positioned such that a plasma transferred arc 130 generated thereby is directed to a target area to preheat the substrate 200 at the target area; and a laser device 410 positioned above the target area to melt the wire to form a molten metal droplet that falls onto the pre-heat zone or molten pool 210.

A wire 155 made of a material forming a workpiece by SFFF is continuously supplied to a laser beam 420 generated by a laser device 410. The wire 155 is supplied by a wire feeder 145 and is positioned such that the end of the wire 155 is above the preheat zone or melt pool 210 at the deposition zone on the substrate 200. The wire 155 may be given a velocity (as indicated by arrow 170) towards the laser beam 420. The speed of the wire 155 may be selected such that the heating and melting rate of the distal end of the wire 155 is such that the molten metal droplets 165 of the molten wire 155 are continuously supplied to the pre-heat zone or molten pool 210.

A laser beam 420 of laser device 410 is directed at the distal end of wire 155 to melt the wire and form molten metal droplet 165. The amount of thermal energy provided by the laser beam 420 can be adjusted to maintain the heating and melting rates according to the feed rate of the wire 155 such that the formation of the molten metal droplets 165 is timed to maintain a continuous drip of molten wire 155 onto the pre-heating zone or molten pool 210. The feed speed of the laser beam 420 and the wire 155 from the wire feeder 145 may be constantly adjusted and controlled by a control system (e.g., a computer) such that the molten wire 155 is supplied to the preheat region or melt pool 210 at a rate that provides a predetermined deposition rate of the metal or metal alloy onto the substrate 200. The wire may be fed into the laser beam at any angle and is not limited to the angle shown in fig. 10. The control system simultaneously engages to operate and adjust the engagement of actuators (not shown) that constantly position and move the substrate 200 so that the pre-heat zone or melt pool 210 is located at a predetermined deposition point given by the CAD model of the object to be formed.

As previously described, in exemplary embodiments, the laser beam may also be manipulated so as to be directed not only to the wire 155, but also to an area in the substrate that is below the dripping molten wire. In this manner, the laser beam may be used to further heat the already preheated region or melt pool produced by the PTA torch 110.

The plasma transferred arc 130 is formed by the PTA torch 110. As shown, the PTA torch 110 can be electrically connected to the power supply 320 such that the torch electrode 120 becomes a cathode and the workpiece 200 becomes an anode. The power supply may be an ac power supply or a dc power supply. The plasma transferred arc 130 can be continuous and directed to heat at least a portion of a target area on the workpiece surface. The preheating of the target surface may make it more receptive to molten metal droplets 165 from the molten wire 155. The preheating of the target surface may melt a portion of the workpiece surface at the target area. The effect of the dc power supply 310 can be adjusted to maintain the heating and/or melting rate according to the target speed of the wire 155 so that the target area is preheated and receives the molten metal droplets 165. The effect supplied by the dc power source 310 and the feed rate of the wire 155 from the wire feeder 145 may be constantly adjusted and controlled by the control system so that the molten wire 150 is supplied to the preheating zone or molten pool 210 at a rate that provides a predetermined deposition rate of the metal or metal alloy onto the substrate 200. At this stage of the SFFF process, the substrate 200 is moved as indicated by arrow 240.

Fig. 10 also depicts an alternative electrical configuration that may generate a heat pulse in the preheat region or melt pool 210. In the illustrated embodiment, the dc power supply 320 may be electrically connected to the PTA torch 110 such that the torch electrode 120 becomes a cathode and the substrate 200 becomes an anode. In addition, a pulse frequency generator 330 for pulsing the power delivered by the dc power supply 330 is positioned in the circuit such that the plasma transferred arc 130 delivers a pulsed heat flux to the target area in addition to heating and optionally melting a portion of the target area on the workpiece surface. The pulse frequency generator 330 may be regulated by the control system. In some embodiments, alternative electrical configurations provide pulsed arc discharge at a frequency of 1 to about 200Hz, but frequencies up to about 1kHz may be used. In some applications, the pulse frequency may be in the range of about 1 to 100Hz, or in the range of about 10 to 100Hz, or in the range of about 5 to 50 Hz.

Using the PTA torch to preheat the substrate and form a preheated region and using a laser beam to melt the feed wire of the metallic material provides the following advantages: the amount of heat supplied to the feeder of the wire can be increased regardless of the amount of heat supplied to the substrate. The melting power applied to the wire may be selected to match the mass input (amount of molten metal droplets to be added to the wire of the workpiece) to ensure stable melting and/or burnout of the wire. Thus, the deposition rate of the molten metal feed can be increased without simultaneously overheating the substrate, and without the risk of splashing or forming excessive pre-heat zones or pools and thus losing control over consolidation of the deposited material.

System comprising two laser devices

In some configurations of the dual torch system provided herein, the system may include two laser devices as heating devices for the two torches. In one configuration, a laser device preheats a target deposition area on the substrate and another laser system heats and melts the wire, forming droplets that drip onto the preheated area or molten pool on the target deposition layer. In another configuration, the laser apparatus preheats a target deposition area on the substrate and the laser torch system heats and melts the powdered metal onto the preheated area or molten pool on the target deposition layer.

In one configuration, the first laser device may be arranged to direct a first laser beam onto a target area of the substrate to form a pre-heat zone, and the second laser device may be positioned to direct a second laser beam onto an end of the wire that is located above the pre-heat zone of the substrate. The thermal energy of the laser beam of the second laser device melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. As discussed in connection with other embodiments, the laser beam of the second laser device used to melt the wire may also be used to contribute thermal energy in a pre-heated region or melt pool in the substrate at the target deposition region, thereby contributing to the thermal energy provided by the laser beam of the first laser device. The laser beam of the first laser device preheats the target area and may promote fusion between the substrate and the molten metal material by deepening the melting of the molten metal droplets into the substrate. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may comprise a wire supply for supplying a wire to a desired position under the laser beam of the second laser device. The wire supply may be located between the first laser device and the second laser device or may be positioned such that it is closer to the second laser device than the first laser device.

The system can also include a positioning device that can position the wire over a pre-heat region formed in the substrate by the first laser device. The positioning device may also suitably place the end of the wire in the laser beam of the second laser device so that the wire suitably melts and so that a droplet of molten metal formed by melting the wire falls onto the preheated area of the substrate therebelow.

The wire may be or contain aluminum, chromium, copper, iron, hafnium, tin, manganese, molybdenum, nickel, niobium, silicon, tantalum, titanium, vanadium, tungsten or zirconium or composites or alloys thereof. In some embodiments, the wire comprises titanium or a titanium alloy. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. The wires may be in any configuration. The wire may have a circular cross-section. The diameter of the wire may be in the range of about 0.8mm to about 5 mm. The wire may have any practically realizable cross-sectional dimension, such as 1.0mm, 1.6mm, 2.4mm, etc. The feed rate and positioning of the wire can be computer controlled to ensure that the wire melts when it reaches a predetermined position above the pre-heat zone or melt pool in the substrate.

The first laser device may generate a laser beam of sufficient energy to deliver thermal energy to a target area of the workpiece to heat and optionally melt at least a portion of the surface such that the target area can receive a molten metal droplet of metal from the molten wire. The second laser device may generate a laser beam of sufficient energy to transfer thermal energy to the wire to melt the wire to form a molten metal droplet. Examples of suitable laser devices may include ytterbium (Yb) lasers, Yb fiber-coupled diode lasers, Yb: glass lasers, diode-pumped Yb: YAG lasers, neodymium-doped ytterbium aluminum garnet (Nd: YAG) lasers, CO2 lasers, CO lasers, Nd: glass lasers, neodymium-doped ytterbium orthovanadate (Nd: YVO) lasers, Cr: ruby lasers, diode-pumped lasers, excimer lasers, gas lasers, semiconductor lasers, solid state lasers, dye lasers, X-ray lasers, free electron lasers, ion lasers, gas mixture lasers, chemical lasers, and combinations thereof. Preferred lasers include Yb lasers, particularly Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers may be less reflective than other laser wavelengths. In some configurations, the first laser device includes a laser of the same material as the second laser device. For example, both laser devices may comprise Yb lasers. In some configurations, the laser of the first laser device is of a different material than the laser of the second laser device.

The first laser device may be configured such that the laser beam it generates may be scanned over the surface of the workpiece in the X or Y direction to cover an area only wider than the focal point of the laser beam. The scan interval may be about 0.001 to about 0.1 inches. The melting behavior of the target region heated by the laser beam of the first laser device can be changed by adjusting the laser device. For example, the power of the laser beam may be adjusted, or the laser beam apparatus may be configured such that the laser beam may be moved relative to the workpiece surface, or the approach direction and angle of the laser beam may be adjusted, or any combination of these may be modified to adjust the preheating of the target area. Any loss of efficiency due to reflection of the laser by the workpiece surface can also be compensated by adjusting the approach direction and angle of the laser beam.

By moving the laser beam of the first laser device along a predetermined path relative to the surface of the workpiece, the area heated by the laser beam layer can be defined in two dimensions on the substrate, the width of the layer being determined by the diameter of the laser beam where it impinges on the substrate. The movement of the laser beam along the predetermined path may be under computer control. Adjusting the pulse shape and/or duration provides a method of controlling the specific power of the laser provided by the first laser device during movement of the laser beam across the surface of the workpiece. The laser beam of the first laser device can also be delivered in pulses. Conventional focusing optics may also be used to adjust the focus of the laser beam on the surface of the workpiece.

The first laser device may be mounted for movement in an X-Y plane parallel to the substrate surface under computer control and for vertical movement in a Z direction orthogonal thereto. Thus, the laser beam of the first laser device may be directed to any point in the X-Y plane and directed vertically to accommodate workpieces of different heights and regions of different heights within the workpiece.

An exemplary embodiment of one configuration is shown in fig. 11, where a laser beam from a laser device preheats a target deposition area on a substrate to form a preheated area, and a laser beam from another laser device heats and melts a wire. In the illustrated embodiment, the substrate 200 shaped as a rectangular cuboid is produced by solid freeform fabrication. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 11 includes: a first laser device 410 positioned such that a laser beam 420 generated by the first laser device is directed to a target area to preheat the substrate 200 at the target area; and a second laser device 430 positioned above the target area to melt the wire 155 to form a molten metal droplet 165 that falls onto the pre-heat zone or molten pool 210.

A wire 155 made of a material forming a workpiece by the free-form fabrication is continuously supplied to a laser beam 435 generated by a second laser device 430. The wire 155 is supplied by a wire feeder 145 and is positioned such that the end of the wire 155 is above the preheat zone or melt pool 210 at the deposition zone on the substrate 200. The wire 155 is given a velocity (as indicated by arrow 170) towards the laser beam 435. The speed of the wire 155 may be selected such that the heating and melting rate of the distal end of the wire 155 is such that the molten metal droplets 165 of the molten wire 155 are continuously supplied to the pre-heat zone or molten pool 210.

The laser beam 435 of the second laser device 430 is directed at the distal end of the wire 155 to melt the wire and form a molten metal droplet 165. The amount of thermal energy provided by the laser beam 435 of the second laser device 430 may be adjusted to maintain the heating and melting rates according to the feed rate of the wire 155 such that the formation of the molten metal droplet 165 is timed to maintain a continuous drop of molten wire 155 into the pre-heating region or molten pool 210. The feed rate of the laser beam 420 and wire 155 from the wire feeder 145 is constantly adjusted and controlled by a control system (e.g., a computer) so that the molten wire 155 is supplied to the preheat region or melt pool 210 at a rate that provides a predetermined deposition rate of the metal or metal alloy onto the substrate 200. The wire may be fed into the laser beam at any angle and is not limited to the angle shown in fig. 11. The control system may be engaged simultaneously to operate and adjust the engagement of actuators (not shown) that constantly position and move the substrate 200 so that the preheat region or melt pool 210 is located at a predetermined deposition point given by the CAD model of the object to be formed.

The first laser device 410 may be mounted to be movable under computer control in an X-Y plane parallel to the substrate surface and vertically in a Z direction orthogonal thereto. Thus, the laser beam 420 of the first laser device 410 may be directed to any point in the X-Y plane on the surface of the workpiece and directed vertically to accommodate workpieces of different heights and regions of different heights within the workpiece. As shown in fig. 11, the lateral direction is the direction of arrow 240, and the apparatus is in the process of manufacturing layer 220.

In a different configuration, the laser device is used as a first welding gun and the laser powder blowing system is used as a second welding gun. The laser device may be arranged to direct a laser beam at a target area of the substrate to form a pre-heat zone, and the laser blowing system heats and melts the powdered metal onto the pre-heat zone or molten pool on the target deposit. The laser beam of the laser apparatus preheats the target area and can promote fusion between the substrate and the molten metal material by deepening the melting of the molten metal droplets into the substrate. The thermal energy of the laser blowing system melts the metal particles, forming molten metal droplets that fall onto a pre-heating region of the substrate below the laser blowing system. The laser soot blowing system may also be used to contribute thermal energy in a pre-heated region or melt pool in the substrate at the target deposition region, thereby contributing to the thermal energy provided by the laser beam of the laser device. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate.

In a laser powder blowing system, metal powder is blown into an interaction region between a laser beam and a workpiece. The powder is typically carried into the laser path by a carrier gas. In some embodiments, a coaxial powder feed nozzle is used. In U.S. patent No. 6,774,338 (Baker et al); 6,608,281 (Ishide et al); 5,486,676 (Aleshin); and U.S. patent application publication No. US2015/0328718 (Iwatani et al); US2005/0056628 (Hu); and US2006/0065650 (Guo) describes an example of a coaxial powder supply nozzle that may be used or modified for use in the system.

The coaxial feed nozzle feeds a stream of metal powder into the nozzle, is directed to the focal point of the laser, heats the powder to a temperature near melting or to a temperature that melts the powder particles into metal droplets that are deposited onto a pre-heated area or melt pool on the workpiece. The laser of the laser apparatus forming the pre-heat zone or melt pool may be pulsed during cooling to alter the microstructure of the added layers to relieve any stress imparted by the added delamination process.

An exemplary embodiment is shown in fig. 8. In the illustrated embodiment, the substrate 200 shaped as a rectangular cuboid is produced by solid freeform fabrication. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 8 includes: a laser device 410 positioned such that a laser beam 420 generated by the laser device is directed to a target area to preheat a portion of the surface of the substrate 200 at the target area; and a coaxial powder feed nozzle laser system 510 positioned above the preheat target zone to form molten metal particles 520 that fall onto the preheat zone or melt pool 210.

A powder delivery system (not shown in the drawings) delivers powdered metal to the coaxial powder feed nozzle laser system 510. The powdered metal is or contains a composition of metals that when melted form the material that forms the workpiece by free-form fabrication. The powdered metal may be titanium or may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The powdered metal may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof.

The powder may be continuously delivered to a laser focus produced by the blow laser system 510 where it is heated to its melting point or completely melted into droplets of molten metal 520 deposited onto the pre-heated region or melt pool 210 on the substrate 200. The speed of the powdered metal provided to the blow laser system 510 is selected such that the heating and melting rates are such that droplets of heated powder or molten metal 520 are continuously supplied to the preheat region or melt pool 210. During cooling, the laser apparatus 410 may be pulsed to adjust the microstructure of the transport layer of molten metal. The two welding guns may be fixed to a single frame so as to always maintain the proper distance.

A dual torch system comprising two laser systems as heating devices may comprise a control system that may operate and adjust the engagement of an actuator (not shown) that may constantly position and move the substrate 200 such that the pre-heated area or melt pool is located at a predetermined deposition point given by a CAD model of the object to be formed. At this stage of the SFFF process, the substrate 200 is moved as indicated by arrow 240. The actuator is movable in an X-Y plane parallel to the dual torch system under control of the control system and is vertically movable in a Z direction orthogonal thereto. The laser focus of laser device 410 is also movable and can be directed to any point in the X-Y plane on the workpiece surface, and directed vertically to accommodate two workpieces of different heights and also to accommodate regions of different heights within the workpiece. An exemplary laser 410 is a Yb fiber laser.

A dual torch system including two laser devices as heating devices may be enclosed in a chamber that is sealed from the ambient atmosphere and may be made substantially oxygen free. An exemplary chamber is described in international patent application publication WO2011/019287 (Guldberg). Weld purge chambers for welding under inert gas are also commercially available (e.g., Soltzbury LC technology solutions, Mass.) and can be easily designed or engineered to accommodate systems of any size or configuration. By using a deposition chamber that is substantially oxygen free, such as argon or other inert gas instead of ambient gas, the speed of the welding process may be increased, as the welding zone may be allowed to reach higher temperatures without risk of excessive oxidation of the weld.

Alternatively, a dual torch system including two laser devices may be configured such that the envelope of shielding gas surrounds the deposition process area to avoid oxidation. In such a system, the nozzle directs a shielding gas (such as argon) to a region surrounding the coaxial powder feed nozzle laser system 510 and the preheat region or melt pool 210. For example, an inert gas may be directed through one or more nozzles located on support 530 to direct the inert gas around the vicinity of the molten weld pool. The gas isolates the preheat zone or bath from the atmosphere to prevent oxidation. Ireland et al (U.S. Pat. No. 7,220,935); comon et al (U.S. Pat. No. 9,145,832); and Cooper et al (U.S. patent application publication No. US 2010/0276396) describe a system that may be used or adapted for use with a dual torch system.

Using a laser device to preheat the substrate and form a preheated area and using another laser device to melt the metal wire or metal particles provides the following advantages: the heat supplied to the metal wires or the metal particles can be increased regardless of the heat supplied to the substrate. The melting power applied to the wire or metal particles may be selected to match the mass input (amount of molten metal droplets to be added to the workpiece) to ensure stable melting and/or burnout of the wire or to ensure complete melting of the metal particles. Thus, the deposition rate of the molten metal feed can be increased without simultaneously overheating the substrate, and without the risk of forming excessive pre-heat zones or melt pools and thus losing control over consolidation of the deposited material.

System comprising a laser device and an electron beam device

In some configurations of the dual torch system provided herein, the system may include a laser device as one torch and an electron beam device as another torch. In some configurations, the electron beam device preheats a target deposition area on the substrate to form a preheated area, and the laser device heats and melts the wire, thereby producing a droplet of molten metal that falls into the preheated area of the target deposition area. In some configurations, a laser device preheats a target deposition area on the substrate to form a preheated area, and an electron beam device heats and melts the wire, thereby producing a droplet of molten metal that falls into the preheated area of the target deposition area.

In one configuration, the electron beam device serves as a first welding torch and may be arranged to direct an electron beam to a target area of the substrate to form a pre-heat zone, and the laser device serves as a second welding torch and may be positioned to direct a laser beam onto the end of the wire located above the pre-heat zone of the substrate. The thermal energy of the laser beam melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. The electron beam of the electron beam device preheats the target area and can promote fusion between the base material and the molten metal material by deepening the molten metal droplet to be melted into the base material. As discussed in connection with other embodiments, the laser beam of the first laser device may also be used to contribute thermal energy in a pre-heat zone or melt pool in the substrate at the target deposition area, thereby contributing to the thermal energy provided by the electron beam. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may comprise a wire supply for supplying a wire to a desired position under the laser beam. The wire supply means may be located between the laser means and the electron beam means or may be located such that it is closer to the laser means than the electron beam means.

The electron beam device may be arranged to direct an electron beam to a target area of the substrate to form a pre-heated area. The electron beam device may generate an electron beam of sufficient energy to transfer thermal energy to a target area of the workpiece to heat and optionally melt at least a portion of the surface so that the target area can accept molten metal droplets of metal from the molten wire. Electron beam devices are commercially available and described in the art (see, for example, U.S. Pat. No. 3,136,882 (Radtke, 1964); No. 3,187,216 (Sciaky, 1965); No. 3,535,489 (Hinriches, 1970); No. 3,592,995 (Hinriches, 1971); No. 3,766,355 (Kottkamp, 1973); No. 4,058,697 (Sokolov et al, 1977); No. 4,327,273 (theta et al, 1982); No. 4,677,273 (Colegrove et al, 1987); No. 4,698,546 (Maitland et al, 1987); No. 6,882,095 (Avnery, 2005); and Taminey and Hafley's "Electron Beam free form fabrication for cost-efficient near-net shape fabrication", NATO, 2006).

The electron beam device may be configured such that the electron beam it generates may be scanned over the surface of the workpiece in the X or Y direction to cover an area only wider than the focal point of the electron beam. The scan interval may be about 0.001 to about 0.1 inches. The melting characteristics of the target area heated by the electron beam can be changed by adjusting the electron beam device. The electron beam device may be selected such that it contains electromagnetic coils to condition the electron beam. The electron beam device may provide energy in the form of a focused stream of electrons that is accelerated toward the workpiece. High voltage potentials (e.g., greater than about 15kV, such as in the range of about 15kV to about 150 kV) can be used to accelerate the electrons. One or more heating wires may be used to generate electrons within the electron beam device. The power output of the electron beam gun can generally be controlled by limiting or adjusting the electron flow to the workpiece. For example, beam power of up to about 30kW may be used, but typically ranges from about 2.5kW to about 10kW or from about 3kW to about 6 kW. The beam current is typically greater than about 100 milliamps and may range from about 100 milliamps to about 600 milliamps. The beam power is variable and is generated by using an input voltage in the range of about 100V to about 500V. An exemplary input voltage of about 110V may be derived by using an input voltage of about 100V to about 600V (e.g., 110V).

By moving the electron beam along a predetermined path relative to the workpiece surface, the area heated by the electron beam layer can be defined in two dimensions on the substrate, the width of the layer being determined by the diameter of the electron beam where it impinges on the substrate. The movement of the electron beam along the predetermined path may be under computer control. Adjusting the beam shape and/or duration provides a method of controlling the specific power provided by the electron beam device during movement of the electron beam across the surface of the workpiece. The electron beam may also be pulsed. As discussed in further detail below, the electron beam device may be moved using mechanical and/or hydraulic actuators to define a pre-heat zone or melt pool in the substrate. Furthermore, the preheating zone or melt pool can also be defined by modulating the electron beam using electromagnetic coils.

The thermal energy of the laser beam of the laser apparatus melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. The laser beam of the laser device may also contribute thermal energy in the vicinity of a pre-heating region of the target deposition area, thereby contributing to the thermal energy provided by the electron beam of the electron beam device. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may comprise a wire supply for supplying a wire to a desired position under the laser beam of the laser device. The wire feed means may be located between the laser means and the electron beam means or may be located such that it is closer to the laser means than the electron beam means.

The system may further include a positioning device that can position the wire over a pre-heat region formed in the substrate by the electron beam device. The positioning device may also suitably place the end of the wire in the laser beam of the laser device so that the wire is suitably melted and so that a droplet of molten metal formed by melting the wire falls onto the preheated area of the substrate therebelow.

The wire may be or contain aluminum, chromium, copper, iron, hafnium, tin, manganese, molybdenum, nickel, niobium, silicon, tantalum, titanium, vanadium, tungsten or zirconium or composites or alloys thereof. In some embodiments, the wire comprises titanium or a titanium alloy. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. In some applications, the wire is free of aluminum. The wire may have any cross-sectional shape. The wire may have a circular cross-section. The wire may have a diameter of up to about 10 mm. The diameter of the wire may be in the range of about 0.8mm to about 5 mm. The wire may have any practically realizable cross-sectional dimension, such as 1.0mm, 1.6mm, 2.4mm, etc. The feed rate and positioning of the wire can be computer controlled to ensure that the wire melts when it reaches a predetermined position above the pre-heat zone or melt pool in the substrate.

The laser device may generate a laser beam of sufficient energy to transfer thermal energy to the wire to melt the wire to form a molten metal droplet. Examples of suitable laser devices may include ytterbium (Yb) lasers, Yb fiber-coupled diode lasers, Yb: glass lasers, diode-pumped Yb: YAG lasers, neodymium-doped ytterbium aluminum garnet (Nd: YAG) lasers, CO2 lasers, CO lasers, Nd: glass lasers, neodymium-doped ytterbium orthovanadate (Nd: YVO) lasers, Cr: ruby lasers, diode-pumped lasers, excimer lasers, gas lasers, semiconductor lasers, solid state lasers, dye lasers, X-ray lasers, free electron lasers, ion lasers, gas mixture lasers, chemical lasers, and combinations thereof. Preferred lasers include Yb lasers, particularly Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers may be less reflective than other laser wavelengths.

An exemplary configuration is shown in fig. 9. In the configuration shown, the substrate 200 shaped as a rectangular cuboid is produced by solid freeform fabrication. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 9 includes: an electron beam device 610 positioned such that an electron beam 620 generated by the electron beam device is directed to a target area to preheat a portion of the surface of the substrate 200 at the target area; and a laser device 410 that generates a laser beam 420 that can heat and melt the wire 155.

A laser beam 420 of laser device 410 may be directed at the distal end of wire 155 to melt the wire and form molten metal droplet 165. The amount of thermal energy provided by the laser beam 420 of the laser apparatus 410 can be adjusted to maintain the heating and melting rates according to the feed rate of the wire 155 such that the formation of the molten metal droplet 165 is timed to maintain a continuous drop of molten wire 155 onto the pre-heating region or molten pool 210. The feed speed of the laser beam 420 and the wire 155 from the wire feeder 145 may be constantly adjusted and controlled by a control system (e.g., a computer) such that the molten wire 155 is supplied to the preheat region or melt pool 210 at a rate that provides a predetermined deposition rate of the metal or metal alloy onto the substrate 200. The wire may be fed into the laser beam at any angle and is not limited to the angle shown in fig. 9. The control system simultaneously engages to operate and adjust the engagement of actuators (not shown) that constantly position and move the substrate 200 so that the pre-heat zone or melt pool 210 is located at a predetermined deposition point given by the CAD model of the object to be formed.

The electron beam device 610 may be mounted to be movable under computer control in an X-Y plane parallel to the substrate surface and vertically in a Z direction orthogonal thereto. Thus, the electron beam 620 of the electron beam device 610 may be directed to any point in the X-Y plane on the surface of the workpiece and directed vertically to accommodate workpieces of different heights and regions of different heights within the workpiece. As shown in fig. 9, the lateral direction is the direction of arrow 240, and the apparatus is in the process of manufacturing layer 220.

In an alternative arrangement, the laser device acts as a first welding torch and may be arranged to direct a laser beam onto a target area of the substrate to form a pre-heat zone, and the electron beam device acts as a second welding torch and may be positioned to direct an electron beam onto the end of the wire located above the pre-heat zone of the substrate. The thermal energy of the electron beam melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. The laser beam of the laser apparatus preheats the target area and can promote fusion between the substrate and the molten metal material by deepening the melting of the molten metal droplets into the substrate. In this embodiment, as discussed with respect to other embodiments, the electron beam of the electron beam device may also be used to contribute thermal energy in a pre-heat zone or melt pool in the substrate at the target deposition area, thereby contributing to the thermal energy provided by the laser beam. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate. The system may comprise a wire supply for supplying a wire to a desired position below the electron beam. The wire supply means may be located between the electron beam means and the laser means or may be located such that it is closer to the electron beam means than the laser means.

An exemplary embodiment is shown in fig. 10. In the illustrated embodiment, the substrate 200 shaped as a rectangular cuboid is produced by solid freeform fabrication. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 10 includes: a laser device 410 generating a laser beam 420 directed to a target area to preheat a portion of the surface of the substrate 200 at the target area; and an electron beam device 710 positioned such that an electron beam 720 it generates can heat and melt the wire 155.

An electron beam 720 of electron beam device 710 may be directed at the distal end of wire 155 to melt the wire and form molten metal droplet 165. The amount of thermal energy provided by the electron beam 720 of the electron beam device 710 can be adjusted to maintain the heating and melting rates according to the feed rate of the wire 155 such that the formation of the molten metal droplet 165 is timed to maintain a continuous drop of molten metal wire 155 onto the pre-heating region or molten puddle 210. The feed rate of the electron beam 720 and the wire 155 from the wire feeder 145 is constantly adjusted and controlled by a control system (e.g., a computer) so that the molten wire 155 is supplied to the preheat region or melt pool 210 at a rate that provides a predetermined deposition rate of the metal or metal alloy onto the substrate 200. The wire may be fed into the electron beam at any angle and is not limited to the angle shown in fig. 10. The control system simultaneously engages to operate and adjust the engagement of actuators (not shown) that constantly position and move the substrate 200 so that the pre-heat zone or melt pool 210 is located at a predetermined deposition point given by the CAD model of the object to be formed.

The laser device 410 may be mounted for movement in an X-Y plane parallel to the substrate surface under computer control and vertically in a Z direction orthogonal thereto. Thus, the laser beam 420 of the laser device 410 may be directed to any point in the X-Y plane on the surface of the workpiece and directed vertically to accommodate workpieces of different heights and regions of different heights within the workpiece. As shown in fig. 10, the lateral direction is in the direction of arrow 240, and the apparatus is in the process of manufacturing layer 220.

In the dual torch system provided herein, including the laser device and the electron beam device, the wire may be or include aluminum, chromium, copper, iron, hafnium, tin, manganese, molybdenum, nickel, niobium, silicon, tantalum, titanium, vanadium, tungsten, or zirconium, or a composite or alloy thereof. In some embodiments, the wire comprises titanium or a titanium alloy. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. The metal may be free of aluminum. The wire may have a circular cross-section. The diameter of the wire may be in the range of about 0.8mm to about 5 mm. The wire may have any practically realizable cross-sectional dimension, such as 1.0mm, 1.6mm, 2.4mm, etc.

In the dual torch system including the electron beam device provided herein, the system includes a housing defining a sealable chamber that may be evacuated, and some or all of the components may be located within the sealable chamber. At least a portion of one or more components (e.g., a control system, a power supply, or a computer) may be located outside of the chamber. The sealable chamber may be configured to enclose a wire feeder, an electron beam device, a laser device, a workpiece, and an actuator tray that moves the substrate relative to at least the first heating device, or an actuator arm that moves the second heating device, or any combination thereof. The chamber may be evacuated as needed for processing. The chamber may be evacuated, for example using a suitable vacuum pump or pumping system, such that the pressure within the chamber is about 1 x 10^-1To about 1X 10^-7Torr or lower. During the deposition process, it may be desirable to reduce the pressure within the chamber to less than about 0.1 torr or less than about 1 x 10^-2Torr or less than about 1 x 10^-6The pressure of the tray.

System comprising two electron beam devices

In some configurations of the dual torch system provided herein, the system comprises: an electron beam device as a first torch for preheating a target deposition area on a substrate; and a further electron beam device as a second welding gun for heating and melting the wire onto the preheating zone or the melt bath. The first electron beam device may be arranged to direct energy to a target region of the substrate to form a melt pool. The first electron beam preheats the substrate to accept a molten metal filament droplet at the location where the molten metal material is to be deposited. In some embodiments, at least a portion of the substrate is melted by the first electron beam device to make the substrate more receptive. In some embodiments, sufficient heat is applied by the first electron beam device to form a pre-heated region or melt pool in the substrate at the location where the metallic material is to be deposited. The first electron beam device may promote fusion between the substrate and the molten metal material by deepening melting in the substrate. The first electron beam device may help to ensure sufficient melting of the overheated molten metal material, which may not be able to achieve sufficient melting by itself. The pre-heating zone or the melt pool, e.g. temperature and size, may be monitored and based on the obtained information, the power of the electron beam device may be adjusted in order to keep the pre-heating zone or the melt pool within desired parameters, such as within predetermined dimensions.

The first electron beam device may be configured such that the electron beam it generates may be scanned over the surface of the workpiece in the X or Y direction to cover an area only wider than the focal point of the electron beam. The scan interval may be about 0.001 to about 0.1 inches. The melting characteristics of the target area heated by the electron beam of the first electron beam device can be changed by adjusting the electron beam device. The electron beam device may be selected such that it contains electromagnetic coils to condition the electron beam. The electron beam device may provide energy in the form of a focused stream of electrons that is accelerated toward the workpiece. High voltage potentials (e.g., greater than about 15kV, such as in the range of about 15kV to about 150 kV) can be used to accelerate the electrons. One or more heating wires may be used to generate electrons within the electron beam device. The power output of an electron beam device can generally be controlled by limiting or adjusting the electron flow to the workpiece. For example, electron beam power of up to about 30kW may be used, but is typically in the range of about 2.5kW to about 10kW or about 3kW to about 6 kW. The beam current is typically greater than about 100 milliamps and may range from about 100 milliamps to about 600 milliamps. The beam power is variable and can be generated by using an input voltage in the range of about 100V to about 500V. An exemplary input voltage is about 110V.

The electron beam device may also be moved using mechanical and/or hydraulic actuators to define a pre-heat zone or melt pool in the substrate.

By moving the electron beam of the first electron beam device along a predetermined path relative to the surface of the workpiece, the area heated by the electron beam of the first electron beam device may be defined in two dimensions on the substrate, the width being determined by the diameter at which the electron beam impinges on the substrate. The movement of the electron beam along the predetermined path may be under computer control. Adjusting the pulse shape and/or duration provides a method of controlling the specific power provided by the electron beam device during movement of the electron beam across the surface of the workpiece. The electron beam may also be pulsed.

The second electron beam device may be arranged to direct an electron beam at the end of the wire located above the molten bath such that thermal energy generated by the electron beam of the second electron beam device melts the end of the wire to form a droplet of molten metal which falls onto a pre-heated region below the end of the wire or onto the molten bath. As discussed in connection with other embodiments, the electron beam of the second electron beam device may also be used to contribute thermal energy in a pre-heat zone or melt pool in the substrate at the target deposition area, thereby contributing to the thermal energy provided by the first electron beam device. The system may comprise a wire supply for supplying wire to the second electron beam device.

The second electron beam device may have a variable power output that is adjustable to provide a substantially constant power or energy to the wire in an amount that provides a substantially constant melting rate of the wire. The power or energy delivered by the second electron beam device may be adjusted according to the composition of the wire so that the wire may be fed and melted at a constant rate onto a preheated region or molten pool on the substrate. The first and second electron beam devices may each independently comprise a single electron beam gun, or each electron beam device may comprise a plurality of electron beam guns. The dual torch system may include one or more detectors, for example, for detecting electrons generated by the electron beam gun or for monitoring the weld puddle, such as a temperature sensor or camera or a detector including a camera, an electronic phenomenon detection mechanism, or a combination thereof.

Electron beam devices are commercially available and described in the art (see, for example, U.S. Pat. No. 3,136,882 (Radtke, 1964); No. 3,187,216 (Sciaky, 1965); No. 3,535,489 (Hinriches, 1970); No. 3,592,995 (Hinriches, 1971); No. 3,766,355 (Kottkamp, 1973); No. 4,058,697 (Sokolov et al, 1977); No. 4,327,273 (theta et al, 1982); No. 4,677,273 (Colegrove et al, 1987); No. 4,698,546 (Maitland et al, 1987); No. 6,882,095 (Avnery, 2005); and Taminey and Hafley, "free-form fabrication of electron beams for cost-efficient near-net-shape fabrication", NATO, 2006). The electron beam device may be selected such that it contains electromagnetic coils to condition the electron beam. The electron beam gun may provide energy in the form of a focused stream of electrons that are accelerated toward the workpiece or wire. High voltage potentials (e.g., greater than about 15kV, such as in the range of about 15kV to about 150 kV) can be used to accelerate the electrons. One or more heating wires may be used to generate electrons within the electron beam device. The power output of an electron beam device can generally be controlled by limiting or adjusting the electron flow to the workpiece or wire. For example, beam power of up to about 30kW may be used, but typically ranges from about 2.5kW to about 10kW or from about 3kW to about 6 kW. The beam current is typically greater than about 100 milliamps and may range from about 100 milliamps to about 600 milliamps. The beam power is variable and is generated by using an input voltage in the range of about 100V to about 500V. An exemplary input voltage is about 110V.

The system may also include a positioning device that can position the wire over a pre-heat zone or melt pool formed in the substrate by the laser. The positioning device can also suitably place the end of the wire in the plasma transferred arc, suitably melting it and causing the formed droplets to fall onto a preheating zone or bath below it.

The wire may be or contain titanium. The wire may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. The wire may be free of aluminum. The wire may have any desired cross-sectional shape. The wire may have a circular cross-section. The diameter of the wire may be in the range of about 0.8mm to about 5 mm. The wire may be of any practical realizable size, e.g., 1.0mm, 1.6mm, 2.4mm, etc. The feed rate and positioning of the wire can be controlled and adjusted according to the effect of the thermal energy provided by the electron beam device to ensure that the wire is continuously heated and melted as it reaches a predetermined location above the pre-heating zone or molten pool in the substrate.

The system may include a housing defining a sealable chamber that may be evacuated, and some or all of the components may be located within the sealable chamber. At least a portion of one or more components (e.g., a control system, a power supply, or a computer) may be located outside the chamber. The sealable chamber may be configured to enclose the wire feeder, the first electron beam device, the second electron beam device, the workpiece, and an actuator tray to move the substrate relative to at least the first heating device or an actuator arm to move the second heating device, or any combination thereof. The chamber may be evacuated as needed for processing. The chamber may be evacuated, for example using a suitable vacuum pump or pumping system, such that the pressure within the chamber is about 1 x 10^-1To about 1X 10^-7Torr or lower. During the deposition process, it may be desirable to reduce the pressure within the chamber to less than about 0.1 torr or less than about 1 x 10^-2Torr or less than about 1 x 10^-6The pressure of the tray.

An exemplary embodiment is shown in fig. 11. In the illustrated embodiment, the substrate 200 shaped as a rectangular cuboid is produced by solid freeform fabrication. The figure shows an initial part of the deposition process during which the first electrode 220 is being deposited. The dual torch system shown in fig. 11 includes a first electron beam device 610 positioned such that an electron beam 620 generated by it is directed to a target area and heats at least a portion of the surface of the target area. In some applications, the electron beam 620 may heat and optionally at least partially melt a portion of the surface of the target region and may help create a pre-heated region or melt pool 210 on the substrate 200 at the target region. The second electron beam device 710 generates an electron beam 720 that is directed onto the end of the wire that is above the pre-heat region of the substrate. The thermal energy of the electron beam 720 melts the end of the wire, forming a molten metal droplet of the wire that falls onto a pre-heating region of the substrate below the wire end. The electron beam 620 of the first electron beam device 610 may promote fusion between the substrate and the molten metal material by deepening the melting of the molten metal droplet into the substrate. The electron beam 720 of the second electron beam device 710 may also contribute thermal energy near the pre-heating region of the target deposition area, thereby contributing to the thermal energy provided by the electron beam 620 of the first electron beam device 610. Superheating from the molten metal droplets may help maintain a molten pool near the pre-heating region of the substrate.

The wire 155 may be supplied by a wire feeder 145 and may be positioned such that the end of the wire 155 is located above the preheat region or melt pool 210 at the deposition region on the substrate 200. The wire 155 may be given a velocity towards the electron beam 720. The speed of the wire 155 may be selected such that the heating and melting rate of the distal end of the wire 155 is such that the molten metal droplets 165 of the molten wire 155 are continuously supplied to the pre-heat zone or molten pool 210.

The wire 155 is a combination of metals or a combination containing metals that when melted form the material forming the workpiece by free-form fabrication. The wire 155 may be titanium or may be or comprise a titanium alloy comprising titanium in combination with one or a combination of aluminum, vanadium, tin, zirconium, molybdenum, niobium, chromium, tungsten, silicon and manganese. For example, exemplary titanium alloys include Ti-6A1-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3 Si. The wire may comprise aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. In some applications, the wire does not include aluminum.

The wire 150 may be continuously fed to an electron beam 720 generated by a second electron beam system 710 where it is heated to its melting point or completely melted into droplets of molten metal 165 deposited into a pre-heated region or molten pool 210 on the substrate 200. The wire may be fed into the electron beam at any angle and is not limited to the angle shown in fig. 11.

The dual torch system may include a control system that may operate and adjust the engagement of an actuator (not shown) that constantly positions and moves the substrate 200 so that the pre-heat zone or melt pool is at a predetermined deposition point given by the CAD model of the object to be formed. At this stage of the SFFF process, the substrate 200 is moved as indicated by arrow 240. The actuator is movable in an X-Y plane parallel to the dual torch system under control of the control system and is vertically movable in a Z direction orthogonal thereto. The focal point of each of the electron beam device 710 and the electron beam device 610 is also movable. For example, changing the focus of the electron beam device 610 may allow the electron beam 620 to be directed to any point in the X-Y plane, as well as vertically adjusted to accommodate two workpieces of different heights and also to accommodate regions of different heights within the workpieces. Changing the focus of the electron beam device 710 may allow the electron beam 720 to be focused on a wire that may be repositioned closer to or further from the surface of the workpiece. During cooling, the electron beam device 610 may be directed onto the cooled molten layer to adjust the microstructure of the transported layer of molten metal.

The first and second electron beam devices may advantageously have separate power supplies and means for regulating the power supplied to the respective devices. The system may include sensors for monitoring the temperature of the deposition area of the substrate, and the width and positioning of the electron beam may be varied over the surface of the molten pool and/or wire or the preheating area.

In the dual torch system provided herein, using a first torch containing a heating device to preheat the substrate and form the preheating zone and using a second torch containing a heating device to melt the wire or metal particles provides the following advantages: the heat supply to the metal wires or metal particles can be increased regardless of the heat supplied to the substrate. The melting power applied to the wire or metal particles may be selected to match the mass input (amount of molten metal droplets to be added to the workpiece) to ensure stable melting and/or burnout of the wire or to ensure complete melting of the metal particles. Thus, the deposition rate of the molten metal feed can be increased without simultaneously overheating the substrate, and without the risk of forming excessive pre-heat zones or melt pools and thus losing control over consolidation of the deposited material.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

List of reference numerals

The following is a list of reference numerals used in the specification and drawings.

110 PTA welding torch

120 welding torch electrode

130 plasma transferred arc

140 wire feeder

145 wire feeder

150 wire

155 wire

160 molten metal droplets

165 molten metal droplet

170 speed arrow

200 base material

210 preheating zone or bath

220 welding rod

240 direction arrow

310 power supply

320 power supply

330 pulse frequency generator

410 laser device

420 laser beam

430 second laser device

440 laser beam

510 powder blowing laser device

520 fused particles

530 support

610 first electron beam device

620 electron beam

710 second electron beam device

720 electron beam

Claims (16)

1. A system for building a metal object by solid freeform fabrication, comprising:

a first torch for preheating a portion of a surface of a substrate;

a wire feeder that supplies wire and positions the wire such that a distal end of the wire is located above the preheated portion of the surface of the substrate;

a second welding gun comprising a laser device or an electron beam device designed to separate or reflect a portion of a laser or electron beam such that the laser or electron beam impinges on the wire for melting the wire into droplets of metallic material deposited onto the preheated surface of the substrate and the laser or electron beam impinges on the substrate to contribute thermal energy to the substrate;

an actuator tray to move the substrate relative to at least the first torch;

a deposition profile of an object to be formed such that the object is built up by fusing successive deposits of the metallic material onto the substrate according to the deposition profile; and

a computer-aided manufacturing system or software that directs movement of the actuator tray in response to the deposition profile,

wherein the first welding gun comprises one of a PTA welding torch, a laser, or an electron beam device.

2. The system of claim 1, further comprising:

an actuator arm to move the first welding gun; or

An actuator arm to move the second welding gun; or

An actuator arm to move the first weld gun and an actuator arm to move the second weld gun.

3. The system of claim 1 or 2,

the first welding torch comprises a PTA welding torch, and the second welding torch comprises a laser device; or

The first welding torch comprises a first laser device and the second welding torch comprises a second laser device; or

The first welding torch comprises an electron beam device and the second welding torch comprises a laser device; or

The first welding torch comprises a laser device and the second welding torch comprises an electron beam device; or

The first torch includes a first electron beam device and the second torch includes a second electron beam device.

4. A system for building a metal object by solid freeform fabrication, comprising:

a first torch for preheating a portion of a surface of a substrate;

a second welding gun comprising a laser device or an electron beam device designed to separate or reflect a portion of a laser or electron beam such that the laser or electron beam impinges a metal source for melting the metal source into droplets of a metallic material deposited onto a preheated surface of the substrate and the laser or electron beam impinges the substrate to contribute thermal energy to the substrate;

a first actuator arm that moves the first torch relative to the substrate or the second torch, or both; or

A second actuator arm that moves the second torch relative to the substrate or the first torch, or both; or

A first actuator arm that moves the first torch relative to the substrate or the second torch, or both, and a second actuator arm that moves the second torch relative to the substrate or the first torch, or both;

an actuator tray to move the substrate relative to at least the first torch;

a deposition profile of an object to be formed such that the object is built up by fusing successive deposits of the metallic material onto the substrate according to the deposition profile;

a computer-aided manufacturing system or software that directs movement of the actuator tray, the first actuator arm, the second actuator arm, or any combination thereof, in response to the deposition profile.

5. The system of claim 4, wherein,

the first welding gun comprises an electron beam device and the second welding gun comprises a PAW welding torch, wherein the PAW welding torch is a PTA welding torch that is electrically connected to a direct current power supply such that an electrode of the PTA welding torch becomes a cathode and the metal source is a wire that becomes an anode; or

The first welding torch comprises a PAW welding torch and the second welding torch comprises an electron beam device; or

The first torch comprises a first electron beam device and the second torch comprises a second electron beam device; or

The first torch includes an electron beam device and the second torch includes a coaxial powder feed nozzle laser system.

6. The system of claim 4 or 5, wherein the second welding gun is designed to contribute thermal energy in the pre-heated surface.

7. The system of any of claims 1, 2, 4, and 5, wherein the first and second welding torches are located on opposite sides of the substrate.

8. A method for manufacturing a three-dimensional object of metallic material by solid freeform fabrication, wherein the object is made by fusing together successive deposits of the metallic material onto a substrate, the method comprising:

defining a deposition profile of the object;

preheating at least a portion of a surface of the substrate using a first torch to form a preheated surface; and

heating and melting a wire using a second welding gun such that molten metallic material is deposited onto the pre-heated surface to form the object by fusing successive deposits of the molten metallic material,

moving a first actuator arm to move the first weld gun relative to the substrate or the second weld gun or both; or

Moving a second actuator arm to move the second torch relative to the substrate or the first torch or both; or

Moving a first actuator arm to move the first weld gun relative to the substrate or the second weld gun or both and moving a second actuator arm to move the second weld gun relative to the substrate or the first weld gun or both,

wherein the second welding gun comprises a laser device or an electron beam device designed to split or reflect a portion of a laser or electron beam such that the laser or electron beam impinges on the wire for melting the wire into droplets of metallic material deposited onto the preheated surface of the substrate and such that the laser or electron beam impinges on the substrate to contribute thermal energy to the substrate.

9. The method of claim 8, further comprising:

moving an actuator tray to move the substrate relative to the first torch or the second torch or both.

10. The method of claim 9, wherein movement of either the actuator tray or the first or second actuator arms is controlled by a computer-aided manufacturing system or software and is responsive to the deposition profile such that the successive deposits of molten metallic material form the three-dimensional object upon solidification.

11. The method of any of claims 8-10, wherein the first welding gun comprises a laser device and the second welding gun is a PTA welding torch electrically connected to a dc power supply such that an electrode of the PTA welding torch becomes a cathode and the wire becomes an anode.

12. The method of any of claims 8 to 10, wherein:

the first welding torch comprises a PTA welding torch, and the second welding torch comprises a laser device; or

The first welding torch comprises a first laser device and the second welding torch comprises a second laser device; or

The first welding torch comprises a first electron beam device and the second welding torch comprises a laser device; or

The first welding torch comprises a laser device and the second welding torch comprises an electron beam device; or

The first torch includes an electron beam device and the second torch includes a coaxial powder feed nozzle laser system.

13. A method for manufacturing a three-dimensional object of metallic material by solid freeform fabrication, wherein the object is made by fusing together successive deposits of the metallic material onto a substrate, the method comprising:

defining a deposition profile of the object;

preheating at least a portion of a surface of the substrate using a first torch to form a preheated surface; and

heating and melting a metallic material using a second welding torch comprising a laser device or an electron beam device such that the molten metallic material is deposited onto the pre-heated surface to form the object by fusing successive deposits of the molten metallic material; and

separating or reflecting a portion of the laser or electron beam of the second torch such that the laser or electron beam impinges upon the wire and the substrate to contribute thermal energy to the substrate,

wherein the first welding gun comprises a PTA welding torch, a laser, or an electron beam device.

14. The method of claim 13, further comprising:

a) moving an actuator tray to move the substrate relative to the first weld gun or the second weld gun or both; or

b) Moving a first actuator arm to move the first weld gun relative to the substrate or the second weld gun or both; or

c) Moving a second actuator arm to move the second torch relative to the substrate or the first torch or both; or

d) any combination of a), b), and c).

15. The method of claim 14, wherein movement of either the actuator tray or the first or second actuator arms is controlled by a computer-aided manufacturing system or software and is responsive to the deposition profile such that the successive deposits of molten metallic material form the three-dimensional object upon solidification.

16. The method of any one of claims 13 to 15, wherein:

the first welding torch comprises a PAW welding torch and the second welding torch comprises an electron beam device; or

The first welding torch comprises a PAW welding torch and the second welding torch comprises a laser device; or

The first torch comprises a first electron beam device and the second torch comprises a second electron beam device; or

The first welding torch comprises an electron beam device and the second welding torch comprises a laser device; or

The first welding torch comprises a laser device and the second welding torch comprises an electron beam device; or

The first welding torch includes a first laser device and the second welding torch includes a second laser device.

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