WO2018118697A1

WO2018118697A1 - Plumeless recoater for three-dimensional printing

Info

Publication number: WO2018118697A1
Application number: PCT/US2017/066743
Authority: WO
Inventors: Thomas Lizzi
Original assignee: The Exone Company
Priority date: 2016-12-23
Filing date: 2017-12-15
Publication date: 2018-06-28

Abstract

A recoater for a powder-layer three-dimensional printer is disclosed. The recoater comprises a powder reservoir, a confinement chamber having a controllable ramp having a distal end, and a pusher, wherein the powder reservoir is adapted to dose a predetermined amount of powder onto the ramp when the confinement chamber is closed so as to contain any pluming that might occur during the dosing of the powder. The ramp is adapted to be rotated so that its distal end engages or nearly engages a surface of a build bed, and the pusher is adapted to push the dosed powder along the ramp and off of the ramp's distal end onto the build bed surface without causing pluming.

Description

Title: Plumeless Recoater for Three-Dimensional Printing

Inventor: Thomas Lizzi

Background

[0001] The present invention relates to powder recoaters adapted for use in three- dimensional printing and three-dimensional printers having such recoaters.

[0002] Background of the Art: There are today various types of three-dimensional printers, i.e. devices that convert electronic representations of three-dimensional articles into the articles themselves by the systematic building-up of one or more materials. The device of the present invention finds particular utility with the types of three-dimensional printers which create three-dimensional articles by selectively binding together preselected areas of successively deposited layers of powder. These types of three-dimensional printers are referred to herein as "powder-layer three-dimensional printers" because the construction of the three- dimensional article by such printers utilizes layers of powders as a build material. Examples of such types of powder-layer three-dimensional printers include, without limitation, the binder-jet three-dimensional printers, the selective sintering three-dimensional printers, and the electron beam melting three-dimensional printers.

[0003] It is to be understood that the term "powder" is also sometimes referred to in the art as "particulate material" or "particles" and the term "powder" is to be construed herein as meaning any such material, by whatever name, that is used in such three-dimensional printers as a layer-forming material. Powder may comprise any type of material capable of taking on the powder form, e.g. metal, plastics, ceramics, carbon, graphite, composite materials, minerals, etc., and combinations thereof. The term "build powder" is used herein to refer to a powder which is used to form the powder layers and from which the article is built in a powder-layer three-dimensional printer.

[0004] During the operation of a powder-layer three-dimensional printer, a first layer of a build powder is deposited upon a vertically indexible build platform and then successive powder layers are deposited one at a time upon the first powder layer. Selected portions of selected powder layers are treated to bind the powders in those portions together as one or more three-dimensional articles are formed. Collectively, the portions of the deposited powder layers which are not bound together are referred to herein as a "powder bed." [0005] The process of forming a powder layer is sometimes referred to in the art, and is referred to herein, as "recoating". The device or combination of devices of a particular powder-layer three-dimensional printer that accomplishes the recoating is sometimes referred to in the art, and is referred to herein, as a "powder recoater" or more simply as a "recoater."

[0006] In some powder-layer three-dimensional printers, each powder layer is formed by transferring a predetermined quantity of build powder from an open-top stationary powder reservoir by first indexing upward a platform which supports the powder within the reservoir a predetermined amount to raise the predetermined quantity above the reservoir walls and then pushing that quantity of powder across the top of the build platform or the powder bed, e.g. by a doctor blade or a counter-rotating roller, to form a powder layer. Examples of such recoaters are described in U.S. Patent 5,387,380 to Cima et al. Such recoaters are generally limited for use with relatively small size powder beds, i.e. those which having recoating direction lengths of under a few tens of centimeters.

[0007] In some powder-layer three-dimensional printers, each powder layer is deposited upon the build platform or upon an extant powder bed by a recoater comprising a traveling powder dispenser which dispenses a build powder through an open slit as it traverses across the build platform or powder bed. Examples of such recoaters are described in U.S. Patent 7,799,253 B2 to Hochsmann et al. Such recoaters may or may not include some device which is adapted to smoothen the top of the powder layer. As used herein, the term "smoothen" is to be interpreted as meaning operating on a quantity of powder so as to do at least one of (a) form at least a portion of the quantity of powder into a layer, (b) make at least a portion of the surface of a layer comprising the quantity of powder less rough, and (c) compress at least a portion of a layer comprising the quantity of powder. A mechanism which smoothens a quantity of powder is referred to herein as a "smoothing device."

[0008] Some powder-layer three-dimensional printers benefit from generally applying radiant energy to the powder bed, e.g. to adjust the temperature the powder bed, to assist in the volatilization of fugitive materials, e.g. the carrier or solvent portion of applied binder systems, from the powder bed, and/or to aid in curing one or more materials present within the powder bed. Accordingly, some makers of such powder-layer three-dimensional printers have found it expedient to mount the radiant energy source on the recoater. Doing so provides the radiant energy source with a controllable carriage for moving the radiant heat source across the powder bed, thus eliminating any need for a separate carriage system. In such arrangements, the radiant energy source can be operated at the same, overlapping, or different times from the operation of the recoater' s powder dispensing mechanisms. [0009] A problem with prior art recoaters which include traveling powder dispensers is that they are not well adapted for use with fine powders. Fine powders, as that term is used herein, are those build powders which are prone to flow problems and/or to agglomeration problems due to the fact that for them surface-related forces are no longer negligible in relation to gravitational forces. In general, fine powders have an average effective diameter of under 20 microns, although for some powder materials having high levels of surface-related forces, the average effective diameter at which they fall within this definition of fine powders is larger than 20 microns. It is to be understood that the surface-related forces do not only include forces by which one particle is inherently attracted to another, but also include the forces arising from materials which at least partially coat a particle's surface, e.g. adsorbed moisture.

[0010] One of the problems encountered with the use of fine powders as build powders is that during the dispensing plumes of the very fine particles arise. These fine powder plumes get caught up in drafts within the three-dimensional printer and eventually deposit their load of fine powders throughout the three-dimensional recoater. In the cases that the three-dimensional printer is not enclosed, these plumes can also escape into the atmosphere around the three- dimensional printer giving rise to safety problems for the operator and contaminating nearby surfaces.

Summary of the Invention

[0010] The present invention provides powder-layer three-dimensional printer recoaters which are adapted for use with fine powders in a manner that substantially decreases or eliminates the plumes that are due to the deposition of the fine build powder onto the build bed. The recoater avoids the dropping of the powder as even a drop of a few millimeters is enough to cause fine powder to plume due to air being entrained or trapped by the falling powder and then escaping in small currents that carry along with them entrained fine powder. In these recoaters, an amount of powder that is sufficient to cover the powder bed one layer deep is first dosed within a closed container onto a ramp (which is the width of the powder bed) that is in the closed position within the closed container to form a dosed powder pile that is the width of the powder bed. Once the dosed powder pile has been formed, the ramp is lowered so that its bottom edge is in contact with a preselected location on the surface of the powder bed. A pusher then pushes the powder onto the powder bed to form a deposited powder pile. In some embodiments, the recoater is moved a preselected distance across the powder bed surface as the powder is being deposited onto the bed surface so that the width of the deposited powder pile is substantially the same as was the width of the dosed powder pile. The pusher is then withdrawn and the ramp raised back to its closed position. In some embodiments, the ramp is segmented along its length so as to have an end section that is articulatable. In such embodiments, after the deposited powder pile has been formed, the ramp is raised and the recoater is repositioned. The end section is rotated downward to form a scraper that engages an edge of the deposited powder pile. The recoater is then moved so that the end section spreads the powder across the powder bed to form a layer. In some embodiments, this layer is then further smoothened and/or compacted using a conventional counter-rotating roller or a tamping foot that is moved across the powder bed.

[0011] The present invention also includes powder-layer three-dimensional printers of which such inventive recoaters are a component.

[0012] The present invention also includes using such inventive recoaters and such inventive powder-layer three-dimensional printers for making articles.

Brief Description of the Drawings

[0015] The criticality of the features and merits of the present invention will be better understood by reference to the attached drawings. It is to be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the present invention.

[0016] FIG. 1A-1F are schematic cross-sectional side views of an embodiment of an inventive recoater above a build bed.

[0017] FIG. 1A depicts the recoater situated above a powder bed in position for applying a new powder layer to the build bed.

[0018] FIG. IB depicts the recoater of FIG. 1A after powder has been dosed from the powder reservoir onto the ramp to form a dosed powder pile within the closed confinement chamber.

[0019] FIG. 1C depicts the recoater of FIG. IB. after the ramp has been lowered and the dosed powder pile has been pushed down the ramp onto the surface of the build bed to form a deposited powder pile.

[0020] FIG. ID depicts the recoater of FIG. 1C after the ramp has been raised back up to close the confinement chamber.

[0021] FIG. IE depicts the recoater of FIG. ID after the recoater has been moved to the right and the end section of the ramp has been lowered to engage the right-hand edge of the deposited powder pile. [0022] FIG. IF depicts the recoater of FIG. IE after the recoater has been moved to the left so that the end section of the ramp has spread the deposited powder pile into a new layer.

[0023] FIG. 2 shows a closer schematic view of the bottom portion of the recoater of FIG. 1A.

[0024] FIGS. 3A and 3B are schematic cross-sectional side views of embodiments similar to those shown in FIGS. IB and 1C, respectively, which include filtered optional exhaust and inlet vents.

Description of Preferred Embodiments

[0025] Some preferred embodiments of the present invention are described in this section in detail sufficient for one skilled in the art to practice the present invention without undue experimentation. It is to be understood, however, that the fact that a limited number of preferred embodiments are described in this section does not in any way limit the scope of the present invention as set forth in the claims.

[0026] It is to be understood that whenever a range of values is described herein, i.e. whether in this section or any other part of this patent document, the range includes its end points and every point therebetween as if each and every such point had been expressly described. Unless otherwise stated, the words "about" and "substantially" as used herein are to be construed as meaning the normal measuring and/or fabrication limitations related to the value or condition which the word "about" or "substantially" modifies. Unless expressly stated otherwise, the term "embodiment" is used herein to mean an embodiment of the present invention.

[0027] FIGS. 1 A- IF are schematic cross-sectional side views of an embodiment of an inventive recoater above a build bed. In FIG. 1 A, the recoater 10 is positioned above a build bed 12. The width of the recoater 10 is in the plane that is perpendicular to the drawing page and is as wide as the build bed 12. The recoater 10 is mounted on a controllable trolley (not depicted) that permits the recoater 10 to be moved across the entire length of the build bed 12.

[0028] FIG. 2 shows a closer view of the recoater 10. The recoater 10 includes a powder reservoir 14 that is full of a build powder 16. A confinement chamber 18 is situated below the powder reservoir 14. A selectively positionable ramp 20 defines and closes off the bottom of the confinement chamber 18. At the bottom of the powder reservoir 14 and situated within the confinement chamber 18 is a selectively controllable valve 22. A vibrator 24 is operably connected to the side of the powder reservoir 14. The vibrator 24 and the valve 22 are operated in conjunction with one another to dose a predetermined amount of the build powder 16 from the powder reservoir 14 onto the ramp 20.

[0029] The ramp 20 is rotatably connected to the wall of the confinement chamber 18 by a first hinge 26. The ramp 20 is adapted to be raised to seal off the bottom of the confinement chamber 18 or lowered to engage a build bed by way of a selectively controllable raising mechanism (not depicted) such as a hydraulic cylinder or electric motor. The ramp 20 includes a fore section 28 and an end section 30 which are rotatably interconnected by a second hinge 32. A selectively controllable hydraulic cylinder 34 is hingedly connected to the end section 30 to allow the end section to be selectively raised and lowered.

[0030] The recoater also comprises a pusher 36 comprising a pusher blade 38 connected to a telescoping arm 40 of a hydraulic cylinder 42.

[0031] Referring now to FIG. IB, a portion of the build powder 16 has been dosed from the powder reservoir 14 by operation of the vibrator 24 through the valve 22 onto the ramp 20 to form a dosed powder pile 44 within the closed confinement chamber 18. Any pluming that may have occurred during the dosing of the build powder 16 is captured within the confinement chamber 18. It is to be understood that the recoater 10 in some embodiments is equipped with one or more sensors (not shown) to detect the amount of powder that has been dispensed onto the ramp 20. For examples, such sensors may detect the weight and/or the volume of the powder that has been dispensed.

[0032] After the plume has settled, as shown in FIG. 1C, the ramp 20 is lowered to engage or nearly engage the surface 46 of the build bed 12 and the pusher is operated to push the dosed powder pile 44 (refer to FIG. IB) onto the surface 46 to form a deposited powder pile 48. No pluming occurs during this operation as no air is either entrained or entrapped within the dosed powder pile 44 as it is moved onto the surface 46 to form the deposited powder pile 48.

[0033] FIG. ID depicts the recoater 10 after the ramp 20 has been raised back up to close the confinement chamber 18.

[0034] FIG. IE depicts the recoater 10 after the recoater 10 has been moved to the right and the end section 30 of the ramp 20 has been lowered to engage the right-hand edge of the deposited powder pile 48.

[0035] FIG. IF depicts the recoater 10 after the recoater 10 has been moved to the left across the build bed 12 so that the end section 30 of the ramp 20 has spread the deposited powder pile 48 to form a new layer 50. This new layer 50 can then be acted upon by the printing mechanism (not depicted) of the three-dimensional printer or it can be further conditioned by a smoothing device. At this point in time, the end section 30 can be raised back into place to seal off the containment chamber 18 and the recoater moved out of the way of the printing mechanism (not depicted).

[0036] Some embodiments include one or more optional exhaust vents for the confinement chamber which are in operable communication with a low pressure source. Such vents make it possible to clear the interior space of the closed confinement chamber of any powder particles which may have become suspended during the dosing of the powder onto the ramp in a much shorter time than may be possible by settling. The filters may be added to the exhaust vents to collect the powder. Preferably, one or more filtered inlets are used in conjunction with the one or more exhaust vents to control the flow of air (or other selected gas) through the confinement chamber. Some embodiments which include one or more optional exhaust vents also include side covers attached to the sides of the ramp which drop down when the ramp is lowered so as to prevent powder from spilling off of the edges of the ramp while it is being pushed and also to prevent air (or other selected gas) from coming in from the sides while the ramp is lowered and the exhaust vent is in an exhausting mode.

[0037] FIGS. 3A and 3B are schematic cross-sectional side views of embodiments similar to those shown in FIGS. IB and 1C, respectively, which include filtered optional exhaust and inlet vents. Referring to FIG. 3A, a recoater 60 is shown just after powder has been dosed to form dosed powder pile 62. A filtered exhaust vent 64 is connected to a low pressure source (not depicted) and is in fluid communication with the interior of the confinement chamber 66. A filtered inlet vent 68 is in fluid communication with the interior of the confinement chamber 66 to permit a controlled amount of air (or other selected gas) to enter into the closed confinement chamber 66. The arrows, e.g. arrow 70, depict the gas flow across the confinement chamber 66 from the inlet vent 68 to the exhaust vent 64.

[0038] Referring now to FIG. 3B, the arrows, e.g. the arrow 72, indicate the gas flow that enters the confinement chamber when the ramp 74 is in the lowered position. Such gas flow sweeps across the dosed powder to the exhaust vent 64 as the powder powder pile 62 is being pushed down the ramp 74 and onto the powder bed surface 76 so as to collect any small amount of pluming that may arise during the pushing process.

[0039] While only a few embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as described in the claims. All United States patents and patent applications, all foreign patents and patent applications, and all other documents identified herein are incorporated herein by reference as if set forth in full herein to the full extent permitted under the law.

Claims

Claims What is claimed is:

1. A recoater for a powder-layer three-dimensional printer comprising a powder reservoir and a selectively closable confinement chamber having a selectively positionable receiving surface, wherein the confinement chamber is adapted to receive upon the receiving surface a powder selectively dispensed from the powder dispenser and to confine within the interior of the confinement chamber pluming of the dispensed powder caused by the act of dispensing.

2. The recoater of claim 1 wherein the receiving surface is a portion of a selectively positionable ramp having a fore section which is pivotably connected to the confinement chamber and an aft section.

3. The recoater of claim 2 further comprising a pusher blade adapted to push a pile of powder dispensed from the powder reservoir onto the receiving surface across the receiving surface.

4. The recoater of claim 2 wherein the aft section is selectively rotatable in relation to the fore section.

5. The recoater of claim 2 further comprising at least one side cover operably connected to the ramp and adapted to cover at least a portion of the area between the ramp and the confinement chamber when the aft section of the ramp is rotated away from the confinement chamber.

6. The recoater of claim 1 further comprising a sensor adapted to detect at least one of the weight and volume of an amount of powder dispensed from the powder reservoir onto the receiving surface.

7. The recoater of claim 1 further comprising an exhaust vent which is in fluid communication with the confinement chamber.

8. The recoater of claim 7 further comprising an inlet vent which is in fluid communication with the confinement chamber.

9. The recoater of claim 8 wherein at least one of the exhaust vent and inlet vent includes a filter.

10. The recoater of claim 1 wherein the recoater is mounted upon a controllable trolley.

11. A method of dispensing a powder during the operation of a powder-layer three-dimensional printer comprising a step of dispensing an amount of powder from a powder reservoir onto a selectively positionable receiving surface of a selectively closable confinement chamber.

12. The method of claim 11 further comprising a step of allowing a portion of the dispensed powder which was caused to be gas-suspended within the confinement chamber during the dispensing step to become unsuspended prior to opening the confinement chamber to a surrounding environment.

13. The method of claim 11 further comprising a step of flowing a gas through the interior of the confinement chamber to remove from the interior of the confinement chamber a portion of the dispensed powder which was caused to be gas-suspended within the confinement chamber during the dispensing step.

14. The method of claim 13 further comprising a step of collecting at least some of the gas- suspended powder with a filter.

15. The method of claim 11 further comprising a step of pushing the dispensed powder across the receiving surface onto a powder bed of the powder-layer three dimensional printer.

16. The method of claim 15 wherein the receiving surface is a portion of a selectively positionable ramp having a fore section which is pivotably connected to the confinement chamber and an aft section, the method further comprising a step of rotating the aft section of the ramp away from the confinement chamber.

17. The method of claim 16 wherein the recoater is mounted upon a controllable trolley, the method further comprising a step of forming a new powder layer on the build bed by spreading across the build bed the dispensed powder that was pushed from the receiving surface onto the build bed.

18. The method of claim 17 wherein the step of forming a new powder layer includes pushing the powder as it is being spread with the aft section of the ramp.

19. The method of claim 18, further including a step of rotating the aft end of the ramp in relation to the fore end of the ramp.

20. The method of claim 16 further comprising a step of using a side shield along the side of the ramp to restrict gas from flowing from the sides of the ramp into the interior of the confinement chamber.