WO2002034465A1

WO2002034465A1 - Method and apparatus for rapidly manufacturing 3-dimensional shaped products using machining and filling process

Info

Publication number: WO2002034465A1
Application number: PCT/KR2001/001527
Authority: WO
Inventors: Bo-Sung Shin; Dong-Yol Yang; Doo-Sun Choi; Eung-Sook Lee; Kyung-Hyun Whang
Original assignee: Korea Institute Of Machinery & Materials
Priority date: 2000-10-25
Filing date: 2001-09-10
Publication date: 2002-05-02
Also published as: AU2001294279A1; KR100383880B1; KR20020032008A

Abstract

It is provided a method for making an article by using cutting tool. A workpiece is mounted. A part of the workpiece is cut by the cutting tool. The space formed by the cutting are filled with filler. The other part of the workpiece is cut by using the cutting tool to form a 3-dimensional shape of the workpiece. The filler is removed so that the article with 3-dimensional shape is obtained.

Description

METHOD AND APPARATUS FOR RAPIDLY MANUFACTURING 3- DIMENSIONAL SHAPED PRODUCTS USING MACHINING AND FILLING

PROCESS

Technical Field

The present invention relates to a method and apparatus for manufacturing 3- dimensional shaped products using a machining process.

Background Art

Rapid manufacturing of a 3-dimensional shaped product refers to the rapid manufacture of a 3-dimensional shaped prototype product, using the same material as that of the actual product. A product manufactured according to this process is called a rapidly manufactured product, in which a prototype, a mock-up, or the like manufactured before its mass-production is primarily included. If the product to be mass-produced requires a complex geometrical shape and a high degree of precision, the rapidly manufactured product as the prototype should have the complex geometrical shape, and the degree of precision thereof should also be very stringent. According to the conventional method of manufacturing such a rapidly manufactured product, a process is performed using RP (Rapid Prototyping; its meaning is to rapidly manufacture a prototype) equipment. This method is largely classified into two types: a method of curing liquid photo-sensitive material by irradiating a laser beam thereon to manufacture a 3-dimensional shaped product; and a method of forming a desired shape by bonding granular or layer solid material. For reference, the rapid manufacturing process refers to a process of manufacturing a 3-dimensional shaped prototype or mold directly from 3-dimensional CAD data using various nonmetallic material such as paper, wax, ABS and plastic, or metallic material. Recently, various processes using metal powder and metal wires as the material, have been developed. In a Stereolithography (SLA) method used in 3D system, Inc., each layer is sequentially laminated by selectively irradiating a laser beam onto liquid photo polymer and then solidifying the photo polymer. This method includes two types: locally irradiating a laser beam (for example, this type is performed in 3D system, Inc., Quadrax corporation, Sony, Inc., Du pont, Inc., etc.); and irradiating a laser beam one layer at a time using an ultraviolet lamp (for example, this type is performed in Cubital,

Inc., Light Sculpting, Inc., etc.), which are the most universally used commercial methods. However, since the photo polymer resin having been solidified during a process is contracted when cured, a twist phenomenon may be generated. Further, in a case where a product having a protrusion(s) is manufactured, a support is required for preventing cured resin from dropping downward since the manufacturing process is performed within a liquid resin barrel. Furthermore, since the used material is resin, it is unsuitable as the functional material due to its low strength.

A method of manufacturing a desired shape using powder material includes a Selective Laser Sintering (SLS) method used in DTM Corp., etc. and a 3-dimensional printing (3DP) method used in Solingen, GmbH, Z, Corp., etc. and developed by MIT.

In the selective laser sintering method, a product is manufactured in a manner of coating powder material of plastic resin and then binding the powder material by irradiating a laser beam. A metal part or mold may be manufactured by using iron powder which is coated with plastic resin. However, in manufacturing the metal part or mold, a post- process such as sintering or Cu infiltration is required. Since a contraction phenomenon due to heat deformation may be generated during the post-process, it is difficult to obtain a desired degree of dimensional precision. In the 3DP method, a product is manufactured in a manner of selectively sprinkling liquid binder over coated powder. Nowadays, a ceramic shell for investment casting can be manufactured directly from ceramic powder, or a part can be manufactured by using starch based powder material. During this process, since a post-process is essential to increase the density and strength of the product, a contraction phenomenon due to heat deformation may be generated.

In a Laminated Object Manufacturing (LOM) method used in Helisys, Inc., a product is manufactured by repeating a process of bonding a sheet of thin paper by using a heated roller and then cutting a predetermined portion of the paper with a laser beam. In this method, there is an advantage in that the material costs are reduced since the material is paper. However, there is a disadvantage in that it takes much time to extract the manufactured product. Since plastic sheet material has been currently developed, a plastic part can be manufactured. However, similarly to the case where the paper is used, there is a disadvantage in that it is difficult to extract the manufactured part.

In a Fused Deposition Manufacturing (FDM) method used in Stratasys, Inc., a part is manufactured in a manner of melting plastic resin material in the form of a filament by passing the material between heated nozzles having a shape similar to that of an extruding metal mold and then attaching the material. There is a disadvantage in that the surfaces of the manufactured part become rough since the material in the form of the filament is used.

Rapid manufacturing processes for directly manufacturing a part or mold of functional material such as metal will be described below. In a Laser Engineered Net

Shaping (LENSTM) method developed by Sandia National Lab., used in Optomec, Inc., and recently commercialized, a part is manufactured in a manner of forming a small melt pool by locally heating a metal substrate using a laser beam and then dropping metal powder using a gas. In this case, there is a disadvantage in that the part is severely deformed upon solidification and the degree of dimensional precision thereof is consequently decreased since the part is manufactured by completely melting the metal substrate. Further, it is impossible to manufacture a part having a protrusion(s) or cantilever(s).

In a Shape Deposition Manufacturing (SDM) method performed in Stanford Univ. and Carnegie Mellon Univ., a metal deposition process is combined with a CNC machining process. According to this method, metal is deposited to form a layer. Subsequently, a portion of the layer is machined to have a desired thickness and boundary shape using multi-axis CNC machining, while the remaining portion of the layer is filled with different metal material. Then, the layer is machined again by the CNC machining to complete one layer. After the one layer is completed, a shot peening process is performed to remove any residual stress. By repeating these procedures, a desired part is manufactured. In this method, there is a disadvantage in that it takes much time to manufacture the part since various processes are included therein. Such manufacturing methods have complex processes. In order to manufacture a precise final product, the product should undergo several processes through expensive equipment. There is a limitation on perfect machining of a 3- dimensional shaped product. In such a machining method, a post-process should be involved upon manufacture of a prototype. There is a further disadvantage in that environmental problems may be induced from a limitation on the used material.

Summary of the Invention

Considering the above matters, an object of the present invention is to provide a method and apparatus for rapidly manufacturing 3-dimensional shaped products, wherein prototypes can be manufactured or job shop type production can be made.

Another object of the present invention is to provide a method of manufacturing 3-dimensional shaped products of plastic or metal using machining and filling processes, wherein its processes are simple and any post-processes may not be required. In order to achieve the above objects, according to an aspect of the present invention, there is provided a method of manufacturing a 3-dimensional shaped product comprising the steps of (1) mounting a workpiece on a workpiece set-up unit with a portion thereof to be machined directed toward a cutting tool, (2) machining the portion to be machined with the cutting tool, (3) filling a space formed by the machining step with filler, (4) moving the workpiece so that another portion thereof to be machined is directed toward the cutting tool, (5) machining another portion with the cutting tool, and (6) removing the filler, wherein the steps of (2), (3) and (4) are performed once, or repeated two or more times.

According to another aspect of the present invention, there is provided an apparatus for manufacturing a rapidly manufactured product using a cutting tool comprising a machining unit provided with the cutting tool, a feed table, a workpiece set-up unit mounted on the feed table, and a control unit for controlling relative motion between the feed table and the cutting tool. In this way, the feed table feeds the workpiece in synchronization with the cutting tool, and the workpiece set-up unit mounted on the feed table includes a rotation shaft portion engaged with the feed table and a workpiece-securing portion for holding the workpiece.

In general machining process, force is large, machining time is short and a machined surface of a product is uniform. Accordingly, nonmetal such as styrofoam, wood and plastic, and metal can be machined. Although phenomena generated upon the machining of a workpiece in the machining process are different depending on the kind of used tools, heat-affected zones hardly appear at positions around a boundary portion of the machined surface by using cutting oil in any case. Therefore, in machining a 3-dimensional shaped product, its machined depth and direction can be controlled by controlling the cutting speed and feed speed of the tool or workpiece. Further, as a high speed machining technique has been widely used, it is preferable to use the machining process. However, in a conventional working method using a machining process, a tool may approach and machine only an arbitrary side surface such as a surface of a metal mold. Accordingly, a 3-dimensional shaped prototype could not be perfectly machined. Therefore, in order to overcome such a limitation, according to the present invention, after one side surface of the workpiece is machined by allowing the tool to approach it, the machined side surface is filled with filler (for example, phase-changeable filler). Then, another side surface is repeatedly machined by using binding force of the filler. By repeating such procedures and then removing the filler, a complex and complete 3-dimensional shaped prototype can be machined with a high degree of precision in a short period of time.

Brief Description of the Drawings

The above and other objects and features of the present invention will be apparent to the skilled in the art from the descriptions of various embodiments of the present invention given in conjunction with the accompanying drawings, in which:

FIG. 1 is a process flowchart for explaining the principle of rapid manufacture of a 3-dimensional shaped product; FIG. 2 is a perspective view of a rapid manufacturing apparatus according to an embodiment of the present invention;

FIG. 3 is a view showing the constitution of a filling unit for the rapid manufacturing apparatus according to the embodiment of the present invention;

FIG. 4 is a perspective view of a workpiece set-up unit for the rapid manufacturing apparatus according to the embodiment of the present invention;

FIGS. 5a, 5b and 5c are conceptual views for illustrating several workpiece setup units;

FIG. 6a is a flowchart of a method of rapidly manufacturing a 3-dimensional shaped product according to an embodiment of the present invention; FIG. 6b is a flowchart of a method of rapidly manufacturing a 3-dimensional shaped product according to another embodiment of the present invention; and

FIGS. 7 (a) to (f) are sequential views for illustrating each process of a method of rapidly manufacturing a 3-dimensional shaped product (fan) according to a further embodiment of the present invention.

Detailed Description of the Embodiments

A representative example of a manufacturing method of the present invention will be briefly explained with reference to FIG. 1. That is, CD a stock is fixed to a workpiece set-up unit; (2) a first surface of the stock is first machined (roughened and finished); the machined first surface is filled with filler; ® a second surface of the stock is positioned by turning the stock in a machining direction (opposite to a cutting tool); © the second surface of the stock is machined (roughened and finished), and then filled with the filler; and © the filler is removed, and a final prototype is then completed. Referring to FIG. 2, an apparatus 10 for manufacturing a rapid manufactured product includes a machining unit 12 and a workpiece set-up unit 14. The machining unit 12 of the rapid manufacturing apparatus 10 includes a cutting tool 16. The cutting tool 16 can be moved in up and down, fore and aft, and left and right directions. The movement of the cutting tool 16 is controlled by a control unit 18. The manufacturing apparatus 10 is provided with a workpiece feed table 20 for allowing the workpiece to be fed. The workpiece set-up unit is mounted on the table 20.

A general NC machine may be used as the machining unit 12. The NC machine uses a CAM program, which is created by using CAD data for NC machining. There are also various tools provided with varying tool diameters used in general light machining, heavy machining, and the like depending on the material to be machined and machining conditions. Various commercial spindles for low-speed, medium-speed and high-speed are also used. In particular, in the case of high-speed machining, a tool (for example, an end mill) with a diameter of 0.1 to 6.0 mm is commonly used, and spindle speed is generally in a range of about 8,000 to 40,000 rpm. However, some spindles which have been developed to achieve 150,000 rpm may also be used.

Although typical control units available from Fanuc, Corp. in Japan and Heidenhein, Corp. in Germany may be used as the control unit 18, any other control units may be used depending on the machining unit. Preferably, a control unit operable directly from a PC is used. Although the degree of control thereof is dependant on machining conditions or the required degree of precision, a PC based control system is uniform and simple to a certain extent.

A general feed table capable of allowing the workpiece to be linearly moved or rotated may be used as the workpiece feed table 20. The workpiece set-up unit 14 is mounted on the workpiece feed table 20.

Referring to FIG. 3, a filling unit 22 is mounted on the workpiece set-up unit 14 for filling a machined portion of the workpiece with filler. The filling unit 22 melts the filler and supplies the molten filler to the workpiece. The filling unit 22 includes a filler tank 24, a supply tube 26 and a hot wire 28 as a heating element. An injection device 30 is further included therein for injecting the filler to fill the machined surface of the workpiece. The injection device 30 is provided with a cylinder 32 and a piston 34. A reservoir 36 is mounted at a distal end of the tube 26. The reservoir 36 is formed to provide a substantially large space between the tube and a gate plate to be described below for allowing the filler to be supplied through the gate plate. An outlet area of the reservoir 36 is preferably constructed so as to generally correspond to that of the gate plate. Furthermore, the gate plate 38 is provided for ensuring a uniform flow of the filler injected from the reservoir 36. The gate plate 38 is a flat plate and provided with a plurality of holes through which the filler is supplied. The hot wire 28 to be used as a heater is disposed around the filler tank 24, the tube 26 and the reservoir 36 to supply heat to the filler therein and improve the flowability or fluidity of the filler.

The workpiece set-up unit 14 shown in FIGS. 2 and 3 is illustrated in detail in

FIG. 4. Referring to FIGS. 2 and 3, the shown feed table 20 includes a left and right mounting device 40 and a fore and aft mounting device 44. An up and down feed device 42 may be further provided below them. The workpiece W is centrally positioned.

FIGS. 5a to 5c are conceptual views for illustrating the workpiece set-up unit (also referred to as a set-up jig or mounting jig). Referring to FIG. 5a, there is shown a set-up jig 128. The jig 128 includes a rotation shaft portion 130 and a workpiece- securing portion 132. The workpiece W is fixed to the workpiece-securing portion 132. In FIG. 5a, a top surface Wa and a bottom surface Wb of the workpiece W are machined. First, the workpiece W is secured to the feed table 20 in the fore and aft, left and right, and up and down directions, and the one surface Wa of the workpiece is then machined. After the machining of the said surface is completed, the said machined surface is filled with filler, and then rotated by 180° about the rotation shaft portion 130. Subsequently, the other surface Wb of the workpiece is machined.

Referring to FIG. 5b, in which there is shown a set-up jig 138. The jig 138 includes a rotation shaft portion 140 and a workpiece-securing portion 142. A workpiece W is fixed to the workpiece-securing portion 142. In FIG. 5b, four surfaces Wa, Wb, Wc and Wd of the workpiece W, which are disposed at 90° from adjacent surfaces, are machined. First, the workpiece W is secured to the feed table 20 in the fore and aft, left and right, and up and down directions, and one surface Wa of the workpiece W is then moved along x- and y- axes. After processing (machining and filling) of the one surface is completed, the workpiece is rotated by 90° about the rotation shaft portion 140. By repeating these procedures of the processing and rotation, the other surfaces Wb, Wc and Wd of the workpiece are sequentially machined.

Referring to FIG. 5c, there is shown a set-up jig 148. The jig 148 includes a rotation shaft portion 150 and a workpiece-securing portion 152. The workpiece- securing portion 152 is provided with jaws 152a. A cylindrical workpiece W is secured to the jaws 152a. In FIG. 5c, after the workpiece W is processed (machined and filled) at a position, the workpiece is rotated by a predetermined angle and then stopped. At that position, the workpiece is processed (machined and filled) again. By repeating these procedures, the workpiece W is processed as a whole.

FIGS. 6a and 6b are flowcharts for illustrating a method of manufacturing a product by fixing the workpiece to the set-up jig, which is formed based on the concept shown in FIG. 5a, and machining and filling the top and bottom surfaces of the workpiece according to an embodiment of the present invention.

FIG. 6a shows a flowchart of a method of manufacturing a product by supplying the filler F from above using the filling unit shown in FIG. 3. Referring to FIG. 6a, the workpiece W is first placed (step 601). The workpiece W is fixed in the fore and aft direction (step 603) and fixed in the left and right direction (step 605).

Then, a first surface of the workpiece is machined (step 607). Force is applied to cause the gate plate 38 to be pushed on the workpiece W and to prevent any leakage of the filler (step 609). The filler F is filled through the gate plate 38 (step 611). After the filler is cured, the gate plate 38 is separated. The workpiece fixed to the workpiece set-up unit is released in the fore and aft direction (step 615), and the workpiece is rotated 180° about a left and right axis (step 617). The workpiece is fixed in the fore and aft direction again (step 619). At this time, a second surface of the workpiece is in a state where it can be machined. After machining of the second surface (step 621), the fixed workpiece W is released in all the directions so that it is separated from the apparatus (step 623). Thereafter, the filler is removed in an appropriate method (step 625), and a prototype is then completed (step 627).

FIG. 6b shows a flowchart of an embodiment including the processes of machining the first surface of the workpiece, rotating the workpiece, and filling the filler from below, differently to the method according to the embodiment shown in FIG. 6a. Referring to FIG. 6b, the gate plate 38 is first placed at a lower position (step 649).

The workpiece W is placed on the gate plate, and mounted on the workpiece set-up unit (step 651). The workpiece W is fixed in the fore and aft direction (step 653) and fixed in the left and right direction (step 655). Subsequently, the first surface of the workpiece is machined (step 657). Then, in order to allow the workpiece W to be rotated, the gate plate 38 which has supported the workpiece is moved downward and separated from the workpiece (step 659). The workpiece fixed to the workpiece set-up unit is released in the fore and aft direction (step 661), and the workpiece is then rotated by 180° about the left and right axis (step 663). The workpiece is fixed in the fore and aft direction again (step 665). Then, the gate plate 38 is pushed upward (step 667). Subsequently, the filler F is applied through the gate plate (step 669), and is then cured.

The filler is supplied upwardly to a space previously formed when machining the first surface of the workpiece. After the rotated and thus upward-facing second surface of the workpiece is machined (step 671), the fixed workpiece W is released in all the directions so that it is separated from the apparatus (step 673). Thereafter, the filler is removed in an appropriate method (step 675), and a prototype is then completed (step

677).

FIG. 7 shows a fan, as an example of the rapidly manufactured product to be processed. Both sides of the fan are complex and 3-dimensionally shaped. Coordinate data for use in the 3-dimensional processing of such a fan can be obtained upon 3-dimensional design of the fan. In order to understand the present invention, the fan is introduced as an example of the rapidly manufactured product. Accordingly, the present invention is not limited only to the processing of fans. It is apparent that rapidly manufactured products of different shapes can be manufactured according to the method of the present invention. Referring to FIG. 7, where there is shown a fan manufacturing method according to an embodiment of the present invention. As shown in FIG. 7 (a), the workpiece W is fixed to the workpiece set-up unit. The workpiece is made of plastic resin such as acrylic resin, which is used for injection molding in practice. As previously illustrated in FIG. 2, the cutting tool attached to the NC machine can perform machining of the workpiece in response to commands from a processing program. A position control unit controls the workpiece, that is, the feed table on which the workpiece is mounted. At this time, the workpiece is synchronized with the tool according to control of the control unit for controlling the feed (that is, position) of the workpiece. Herein, "synchronization" means that the workpiece can be automatically machined simply by rotating the cutting tool since the table to which the workpiece is fixed is simultaneously moved along x- and y-axes in machining tools (for example, NC milling machine). On the contrary, it is possible to perform the different format of synchronization so that the workpiece can be machined by controllably rotating the cutting tool and simultaneously moving it along x- and y-axes. Then, the machining system is operated as shown in FIG 7 (b). The machining depth and feed speed of the workpiece can be optimized by selecting the cutting tool depending on material to be machined and precisely controlling its position. As shown in FIG. 7 (b), all the relevant areas on the first surface of the workpiece are machined while controlling the position of the workpiece. At this time, the workpiece is machined in synchronization with its position. Accordingly, 3-dimensional processing can be accomplished perfectly. As shown in FIG. 7 (c), a machined space in the machine surface of the workpiece is filled with the filler F. At this time, thermoplastic resin which has a melting point lower than that of the plastic resin used for the workpiece W, wax, or water-soluble resin, for example, soluble support resin which is soluble in water at room temperature is used as the filler F. In case of a metal workpiece, material with excellent adhesion force and a melting point lower than that of the workpiece is used as the filler. For example, in the case of Al workpiece, a Bi alloy is used as the filler.

As shown in FIG. 5 (d), the workpiece mounted on the workpiece set-up unit is rotated by 180° once again. That is, in order to locate a second surface to be machined in place, the workpiece is rotated by and fixed to the workpiece set-up unit. Next, as shown in FIG. 5 (e), the second surface is machined. Thus, all the intended surfaces have been machined. At this time, the workpiece is machined so as to have a perfectly 3-dimensional shaped fan. Then, the filler is removed, so that the fan as a final product is completed. In a case where the soluble support resin is used as the filler, the completed fan can be separated by solving the resin in the water. In the above embodiment, the filler serves as a general fixture for allowing the workpiece to be maintained in shape until the process is completed.

In the meantime, in addition to the above melting method, the filler and the workpiece can be easily separated using the other methods. For example, in the above embodiment, parting chemicals may be coated, before the application of the filler between the filler and the surfaces remaining as portions of the fan. Then, the filler and the final fan can be easily separated at a later date.

Thus, according to the constitution of the present invention, the 3-dimensional shaped product as the rapidly manufactured product can be manufactured using the machining and filling processes. In particular, the present invention is suitable for manufacturing a plastic or metallic prototype, or facilitating fast job shop type production. The process for rapidly manufacturing the 3-dimensional shaped product becomes simple, and the 3-dimensional shaped prototype of plastic resin or metal can be manufactured without any separate metal mold. Furthermore, the 3-dimensional shaped prototype can be easily manufactured by processing each surface of the rapidly manufactured product using the workpiece set-up unit of the present invention.

Although the present invention has been described in connection with the various embodiments, the present invention is not limited thereto. It is understood by those skilled in the art that various modifications and changes to the present invention may be made without departing from the spirit and scope of the invention, and these modifications and changes also fall within the scope of the present invention.

Claims

1. A method of manufacturing a 3-dimensional shaped product, comprising the steps of: (1) mounting a workpiece on a workpiece set-up unit with a portion thereof to be machined directed toward a cutting tool;

(2) machining the portion to be machined with the cutting tool;

(3) filling a space formed by the machining with filler;

(4) moving the workpiece so that another portion thereof to be machined is directed toward the cutting tool;

(5) machining the another portion with the cutting tool; and

(6) removing the filler, wherein the steps of (2), (3) and (4) are performed once, or repeated two or more times.

2. The method as claimed in claim 1, wherein the workpiece is fed to be machined in synchronization with the cutting tool.

3. The method as claimed in claim 1, wherein in the filling step, the filler is supplied from above to the machined space existing in the machined portion.

4. The method as claimed in claim 1, wherein in the filling step, the filler is supplied from an unmachined portion to the machined space.

5. The method as claimed in any one of claims 1 to 4, wherein the workpiece is a plastic stock, and the filler is thermoplastic resin, wax, or resin which is easily soluble in water.

6. The method as claimed in any one of claims 1 to 4, wherein the workpiece is an Al or Al alloy stock, and the filler is a Bi alloy.

7. An apparatus for manufacturing a rapidly manufactured product using a cutting tool, comprising: a machining unit provided with the cutting tool; a feed table; a workpiece set-up unit mounted on the feed table; and a control unit for controlling relative motion between the feed table and the cutting tool, wherein the feed table feeds the workpiece in synchronization with the cutting tool, and the workpiece set-up unit mounted on the feed table includes a rotation shaft portion engaged with the feed table and a workpiece-securing portion for holding the workpiece.

8. The apparatus as claimed in claim 7, further comprising a filler supply unit for supplying the filler to the workpiece fixed to the workpiece set-up unit, wherein the filler supply unit comprises a filler container, a supply tube connected with the filler container to form a filler supply path, an injection unit provided on the filler supply path, and a gate member mounted at a position close to the workpiece for ensuring a uniform flow of the filler supplied to the workpiece through the tube.