Apparatus and method for manufacturing three dimensional structure

Abstract

To obtain a technique capable of confirming a printing pattern of a binder in a binder jet method.SOLUTION: The 3D printer 100 includes a stage 10, a hopper 12 constituting a means for forming a raw material powder layer PL on the stage 10, an inkjet dispenser 14 for supplying a liquid binder B to the raw material powder layer PL, and a camera 16 for photographing a portion of the raw material powder layer PL to which the binder B is supplied, wherein the liquid binder B contains a coloring material for identifying a portion of the raw material powder layer PL to which the binder B is supplied and a portion of the raw material powder layer PL to which the binder B is not supplied in a photographed image photographed by the camera 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technology for manufacturing a three-dimensional structure using powder as a raw material. [Background technology]

[0002] There is a binder jet method in which a binder is printed on layered raw material powder to form a powder compact in which the raw material powder and binder are bonded together, and the powder compact is sintered to obtain a three-dimensional structure.

[0003] The binder jet method can be carried out efficiently and at low cost, and has been particularly well developed and put into practical use in recent years (see Patent Documents 1 and 2, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-120475 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-522331 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a technique that enables confirmation of a binder print pattern in a binder jet method. [Means for solving the problem]

[0006] The present invention is a three-dimensional structure manufacturing device comprising a stage, a means for forming a raw material powder layer on the stage, a means for supplying a liquid binder to the raw material powder layer, and an imaging means for photographing the portion of the raw material powder layer to which the binder has been supplied, wherein the liquid binder contains a coloring material for distinguishing, in an image taken by the imaging means, between the portion of the raw material powder layer to which the binder has been supplied and the portion to which the binder has not been supplied.

[0007] In one embodiment of the present invention, the coloring material is a pigment or a dye. In another embodiment of the present invention, the coloring material is selected so that the color of the portion of the raw material powder layer to which the binder has been supplied is complementary or opposite to the color of the portion of the raw material powder layer to which the binder has not been supplied. In another embodiment of the present invention, the present invention further includes a control unit that supplies the binder again to the raw material powder layer based on the captured image.

[0008] In the present invention, the formation of the raw material powder layer, the supply of the binder to the raw material powder layer, and the photographing are repeated N times, where N is a natural number not including 0, and an embodiment includes an image analysis unit that analyzes the photographed image obtained by the Nth photographing, and a control unit that adjusts the conditions for the (N+1)th supply of the binder to the raw material powder layer based on the analysis of the photographed image.

[0009] In the present invention, the raw material powder layers are stacked in multiple layers to form a laminate, and the photographing means may include a three-dimensional model creation means that photographs the pattern of the portion of each of the raw material powder layers stacked in multiple layers to which the binder has been supplied, and creates a three-dimensional model of the portion of the laminate to which the binder has been supplied based on the photographed image of the pattern.

[0010] The present invention can also be understood as a method for manufacturing a three-dimensional structure, which includes steps of forming a raw material powder layer on a stage, supplying a liquid binder to the raw material powder layer, and photographing the portion of the raw material powder layer to which the binder has been supplied, wherein the liquid binder contains a coloring material for distinguishing, in a photographed image obtained by photographing, between the portion of the raw material powder layer to which the binder has been supplied and the portion to which the binder has not been supplied. [Effects of the Invention]

[0011] According to the present invention, a technique is provided that allows the printing pattern of the binder to be confirmed in the binder jet method. [Brief explanation of the drawings]

[0012] [Figure 1] Conceptual diagram of a binder jet 3D printer using the invention [Figure 2] 10 is a flowchart illustrating an example of a procedure for 3D printing processing. [Figure 3] 1A to 1C are diagrams illustrating a manufacturing process for a three-dimensional structure using powder raw materials. [Figure 4] 1A to 1C are diagrams illustrating a manufacturing process for a three-dimensional structure using powder raw materials. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1. First embodiment (overview) The 3D printer 100 shown in Figure 1 comprises a stage 10, a hopper 12 that constitutes a means for forming a raw powder layer PL on the stage 10, an inkjet dispenser 14 that supplies a liquid binder B to the raw powder layer PL, and a camera 16 that photographs the portion of the raw powder layer PL to which the binder B has been supplied, and the liquid binder B contains a coloring material that allows the portions of the raw powder layer PL to be distinguished from the portions to which the binder B has not been supplied in the image captured by the camera 16.

[0014] (Hardware configuration) Figure 1 shows a binder jet type 3D printer 100 utilizing the present invention. The 3D printer 100 includes a stage 10 that can be electrically moved up and down. The stage 10 includes a printing stage 11 that functions as a surface on which a three-dimensional structure made from powder is formed.

[0015] In the space above the printing stage 11, a hopper 12 that can move horizontally relative to the printing stage 11 and an inkjet dispenser 14 are arranged. The hopper 12 is a supply means for the raw material powder P. As the hopper 12 moves horizontally relative to the printing stage 11, the raw material powder P is dispersed from the hopper 12 onto the printing stage 11 by gravity fall.

[0016] The layer of raw material powder scattered on the printing stage 11 is spread on the printing stage 11 to a predetermined specific thickness by a roller 13 moving in the horizontal direction, thereby forming a raw material powder layer PL having a specific thickness.

[0017] Liquid binder B is sprayed from an inkjet dispenser 14 onto the raw powder layer PL in a specific, predetermined printing pattern. This state is shown in Figure 1(B). Binder B is an aqueous solution containing an organic binder and a coloring material, and corresponds to the ink liquid of a printer. In this example, a dye or pigment is used as the coloring material. The inkjet dispenser 14 corresponds to the ink supply head of a printer, has an XY stage movement mechanism in the horizontal direction, and can be electrically moved left and right and in the depth direction of the figure.

[0018] While moving the inkjet dispenser 14 in the left-right direction in the figure, the binder B is sprayed from the inkjet dispenser 14 onto the raw powder layer PL in a specific spray pattern (see FIG. 1(B)). This forms a specific print pattern of the binder B in a linear region of the raw powder layer PL. By repeating the above process while shifting the inkjet dispenser 14 in the depth direction in the figure, a specific print pattern PLa of the binder B is formed on the raw powder layer PL.

[0019] The 3D printer 100 is equipped with a camera 16. After printing the binder B described above, the camera 16 photographs the surface of the raw material powder layer PL, which is the printing surface, from above. The camera 16 captures a color image (RGB image). As described above, the liquid binder B contains a coloring material, and this coloring material makes it possible to distinguish the printing pattern PLa of the binder B from the raw material powder layer PL in the photographed image.

[0020] The coloring material is selected so that the color tone of the print pattern PLa of the binder B can be distinguished from the raw material powder layer PL in the captured image. That is, the coloring material is selected so that the color of the portion of the raw material powder layer PL to which the binder B has been supplied (the portion of the print pattern PLa) can be distinguished from the color of the portion of the raw material powder layer PL to which the binder B has not been supplied (the portion not of the print pattern PLa) in the captured image. For example, a coloring material is selected so that the color of the print pattern PLa is a complementary or opposite color to the color of the raw material powder P. Image data of the image captured by the camera 16 is sent to the control system 20, which will be described later.

[0021] The 3D printer 100 is equipped with a heater 15, which is a heating means. By moving the heater 15 horizontally above the raw material powder layer PL onto which the binder B has been selectively sprayed, the print pattern PLa is subjected to a heat treatment, and the print pattern PLa is hardened by the function of the binder B.

[0022] The 3D printer 100 is equipped with a light-emitting unit 17, which is an illumination means. The light-emitting unit 17 is configured, for example, with an LED light-emitting element. The light-emitting unit 17 is selected to emit light of a wavelength that enhances the distinguishability of the print pattern PLa.

[0023] The 3D printer 100 includes a control system 20. The control system 20 is a computer equipped with a CPU, a data storage unit, and various interfaces. As shown in FIG. 1(C), the control system 20 includes a control unit 21 and an image analysis unit 22 as functional units. These functional units are realized when the CPU of the computer executes programs for realizing the corresponding functions.

[0024] The control unit 21 controls the operations of the hopper 12, the inkjet dispenser 14, the heater 15, the camera 16, and the light emitter 17. The image analysis unit 22 analyzes the image captured by the camera 16, acquires information about the print pattern PLa in the raw powder layer PL of the binder B discharged from the inkjet dispenser 14, and further determines whether or not there is an abnormality in the print pattern PLa.

[0025] (Raw material powder) Examples of raw material powders include metal powders and alloy powders, especially steel powder. The raw material powders vary depending on the desired product, which is a sintered body. For example, if the product is a die, an alloy powder of alloy steel for hot die work, such as SKD61, can be used. Furthermore, if the product is a cast steel, high-tensile carbon steel cast iron, such as SCC material, can be used. Other examples include, but are not limited to, at least one of metal powders and alloy powders commonly used in MIM (metal injection molding) processes, such as stainless steel and Inconel (registered trademark), carbonyl iron powder, carbonyl nickel powder, nickel-based alloy powder, cobalt-based alloy powder, copper and copper alloy powder, aluminum and aluminum alloy powder, titanium and titanium alloy powder, magnesium and magnesium alloy powder, and ceramic powder. An example of a suitable raw material powder is water-atomized powder. The average particle size of the raw material powder is, for example, 3 to 50 μm.

[0026] (Example of manufacturing process) Fig. 2 is a flowchart showing an example of the procedure for 3D printing processing using the 3D printer 100. The program for executing the processing in Fig. 2 is stored in the data storage unit of a computer constituting the control system 20 and executed by the CPU of the computer. Figs. 3 and 4 are diagrams showing the manufacturing process of a three-dimensional structure using the 3D printer 100.

[0027] First, raw material powder is supplied onto the printing stage 11 to form a raw material powder layer PL (step S101: FIG. 2(A)). Next, a roller 13 is used to flatten the raw material powder layer PL and make it have a specified thickness (step S102: FIG. 2(B)). Here, the thickness of the raw material powder layer PL after flattening is set to 100 μm. The thickness of the raw material powder layer PL after flattening is selected from the range of 50 μm to 200 μm, for example.

[0028] Next, the binder B is printed onto the raw powder layer PL in a predetermined printing pattern (step S103: FIG. 2(C)). FIG. 2(C) shows a state in which the binder B has been sprayed onto the portion indicated by the symbol PLa.

[0029] At the same time as binder B is printed, camera 16 photographs the printed surface (step S104). The photograph may be taken after printing of binder B is completed. This photographing allows image data of the print pattern of binder B to be obtained. During this photographing, light-emitting unit 17 is used to illuminate the surface to be photographed. The print pattern in the photographed image is recognized using image recognition software (step S105).

[0030] Next, the photographed print pattern is subjected to image analysis to determine whether there are any abnormalities in the print pattern (step S106). Here, the image analysis determines whether there is an oversupply or undersupply of binder B, whether there are any unevenness in the binder within the print pattern, whether there are any missing parts in the print pattern, and whether there is any binder spilling or bleeding from the print pattern.

[0031] If the print pattern is determined to be "normal," a process of hardening the binder is performed (step S107: FIG. 3(D)). This process is performed by passing a heater 15 above the raw material powder layer PL. By hardening the binder, a hardened layer 30 is formed in which the raw material powder is hardened.

[0032] By repeating the processes of steps S101 to S107, a stack of raw material powder layers on which hardened layers have been formed is obtained. FIG. 3(F) shows a state in which raw material powder layers PL are stacked in two layers, and hardened layers 31 and 32 of raw material powder are stacked with a slight shift in position. FIG. 4(A) shows a stack 33 in which raw material powder layers on which hardened layers (hatched areas) have been formed are formed in multiple layers. The number of layers to be stacked is determined by the thickness dimension of the final product. For example, if the thickness of one layer is 100 μm and the thickness of the final product is 10 mm or more, 100 or more layers will be stacked.

[0033] After the binder curing process, it is determined whether the number of raw material powder layers PL has reached a predetermined specified number of layers (step S108). If the number of layers has reached the specified number, the stage 10 is raised and the uncured portions of the raw material powder layers PL are sucked and removed using a suction nozzle (not shown) (step S109). The portions of the raw material powder layers PL where the binder B is not printed are not cured and remain as fluid powder, and are removed by the above suction. By removing the uncured raw material powder, a stack 34 of cured layers of raw material powder is obtained, as shown in FIG. 4(B).

[0034] Once the laminate 34 of the cured layers of the raw material powder is obtained, it is removed from the 3D printer 100 and subjected to a sintering process by heating to 1300°C to 1400°C (step S110). This process integrates the laminate 34, and a sintered body 35 having a three-dimensional structure made from the powder as the raw material, as shown in FIG. 4(C), is obtained.

[0035] After the sintering process, HIP (hot isostatic pressing) may be performed, for example, at 1150°C, 100 MPa, and for about 3 hours.

[0036] If it is determined in step S108 that the specified number of layers has not been reached, the process returns to the stage before step 101, and the processes from step 101 onwards are repeated to form the next layer. At this time, the stage 10 is lowered by the thickness of the raw material powder layer PL flattened in step S102, and the processes from step 101 onwards are executed again. This allows the next layer to be formed.

[0037] If the determination in step S106 is that "there is an abnormality in the print pattern," the following processing is performed. In this case, it is first determined whether corrective printing is possible (step S111). Corrective printing involves additional printing to correct the print pattern. For example, if there is a gap in the print pattern, corrective printing is performed to fill in that gap. Note that in cases such as an oversupply of binder, the abnormality in the print pattern cannot be resolved by additional printing. In this case, the determination in step S111 is NO. If corrective printing is possible, the determination in step S111 is YES.

[0038] If corrective printing is not to be performed, the printing conditions for the next layer are corrected (step S112), and the process proceeds to step S107. In step S112, the printing conditions are changed to correct the abnormality in the print pattern determined in step S106. For example, if it is determined that the binder supply is excessive, the settings are corrected to reduce the binder supply amount (discharge amount). In this case, the amount of binder discharged from the inkjet dispenser 14 in the process of step S103 when forming the next layer is reduced.

[0039] If it is determined in step S111 that corrected printing is to be performed, the printing conditions for the corrected printing are set (step S113), and printing is performed again (additionally) under those conditions in step S103. The printing conditions for the corrected printing are set as conditions for correcting the abnormality in the print pattern determined in step S106.

[0040] (superiority) In this embodiment, in a 3D printer using the binder jet method, the binder to be jetted is colored, and the pattern (printing pattern) of the area where the binder jetting is performed is image-recognized. This allows real-time monitoring of whether the binder jetting is being performed accurately. Furthermore, if the binder jetting is not being performed accurately, additional printing is performed on the layer in question, or the binder jetting conditions for the next layer are corrected.

[0041] 2. Second embodiment In the first embodiment, a fluorescent material is used as the coloring material. In this case, the fluorescent material is contained in the binder, and light of a wavelength that generates fluorescence from the fluorescent material is emitted from the light-emitting unit 17. By using fluorescence, the presence or absence of binder B depending on the location in the raw powder layer PL can be clearly identified on the captured image.

[0042] 3. Third embodiment In the first embodiment, an infrared camera is used as the camera 16, and infrared light is emitted from the light-emitting unit 17. Metals reflect infrared light (approximately wavelengths of 800 nm or more) with high efficiency. Furthermore, binder components are organic, and their reflection efficiency for infrared light is not as high as that of metals. Therefore, when metal powder or alloy powder is used as the raw material powder, differences in the reflection characteristics of infrared light occur between the portion of the raw material powder layer where the binder is introduced and the portion where it is not, and both can be distinguished in the infrared image. Examples of the wavelength of the infrared light used include approximately 1 μm to 10 μm. In this case, the organic component of the binder functions as a colorant. In this embodiment, a material with high infrared absorption efficiency (e.g., carbon powder) may be used as the colorant.

[0043] 4. Fourth Embodiment In the first embodiment, a plurality of inkjet dispensers 14 with different colorings are prepared. In this case, prior to step S103 in Fig. 4, an image of the raw material powder layer PL is taken by the camera 16 to obtain data on the color tone of the raw material powder layer PL. Based on this data, a color of binder B that is highly distinguishable from the raw material powder layer PL is selected.

[0044] 5. Fifth Embodiment A material that colors the raw powder through a chemical reaction is added to the binder as a coloring material. For example, a technique for coloring a metal by forming an oxide film on the metal surface or by depositing a coating is known. When a metal powder or alloy powder is used as the raw powder, the coloring material used in the above technique is added to the binder. In this case, the binder print pattern formed on the raw powder layer is colored by a chemical reaction.

[0045] 6. Sixth Embodiment In the first to fifth embodiments, information on the two-dimensional distribution of the binder print pattern PLa in each raw material powder layer PL is obtained as image information. By overlapping this two-dimensional distribution information in the height direction, three-dimensional model data of the portion of the raw material powder layer stack 33 shown in FIG. 4(A) where the binder has been introduced (corresponding to the stack 34 in FIG. 4(B)) is obtained. This three-dimensional model not only represents the final shape of the stack 34, but also the shape during the stacking process. When implementing this embodiment, for example, a three-dimensional model creation unit is provided in the control system 20.

[0046] An example of the procedure for creating a three-dimensional model of the portion where the binder has been introduced will be described below. Here, information on the printing pattern of the binder in each of the raw material powder layers that make up the laminate 33 shown in FIG. 4 is obtained from images captured by the camera 16. Then, the printing pattern of the binder in each raw material powder layer is converted into data as a thin three-dimensional structure having the thickness of the raw material powder layer (e.g., 100 μm). By creating data that stacks these thin three-dimensional structures in the thickness direction, a three-dimensional model of the portion where the binder has been introduced can be obtained.

[0047] This three-dimensional model is used for the following purposes, for example. The above three-dimensional model can be obtained not only at the final stage but also during the lamination process. For example, if 100 layers are to be laminated, a three-dimensional model of the binder-introduced portion is obtained every fifth layer, from the 5th layer, 10th layer, 15th layer, to the 100th layer (hereinafter referred to as the measured three-dimensional model).

[0048] On the other hand, a three-dimensional model of the planned laminate of the binder print pattern (hereinafter referred to as the planned three-dimensional model) is obtained based on a control program that controls the binder print pattern (a control program that controls the position of the inkjet dispenser 14). Then, in the process of laminating every five layers, the measured three-dimensional model is compared with the planned three-dimensional model to monitor whether the work is being carried out as planned. The timing for comparing the measured three-dimensional model with the planned three-dimensional model is not limited to the above example.

[0049] Next, we will explain another example using the three-dimensional model of the portion where the binder is introduced. In the binder jet method, shrinkage occurs during sintering, causing changes in the dimensions of the compact. This shrinkage is related to the type of raw material powder, the shape and dimensions of the compact, sintering conditions, etc., and may occur at a level that requires attention, or may be negligible.

[0050] Here, a three-dimensional model based on a photographed image of the binder print pattern described above is compared with a three-dimensional model of the sintered body 35 to obtain information on the shrinkage. The three-dimensional model of the sintered body 35 can be obtained, for example, by three-dimensional stereophotography. This method makes it possible to obtain information on differences in local shrinkage of the laminate. Based on this shrinkage information, the conditions of the binder jet process shown in FIG. 3 can be adjusted to improve the dimensional accuracy of the sintered body 35. [Industrial Applicability]

[0051] The present invention can be used in 3D printing technology using the binder jet method. [Explanation of symbols]

[0052] 100...3D printer, 10...stage, 11...printing stage, 12...hopper, 13...roller, 14...inkjet dispenser, 15...heater, 16...camera, 17...light emitting unit, 20...control system, 21...control unit, 22...image analysis unit, PL...raw material powder layer, B...binder, PLa...portion of raw material powder layer PL where binder is introduced (binder printing pattern).

Claims

1. The stage and a means for forming a raw material powder layer on the stage; a means for supplying a liquid binder to the raw material powder layer; an imaging means for imaging a portion of the raw material powder layer to which the binder has been supplied; Equipped with A three-dimensional structure manufacturing apparatus, wherein the liquid binder contains a coloring material for distinguishing between areas in the raw material powder layer to which the binder has been supplied and areas to which the binder has not been supplied in the captured image taken by the photographing means.

2. 2. The apparatus for manufacturing a three-dimensional structure according to claim 1, wherein the coloring material is a pigment or a dye.

3. 2. The three-dimensional structure manufacturing apparatus according to claim 1, wherein the coloring material is selected so that the color of the portion of the raw material powder layer to which the binder is supplied is complementary or opposite to the color of the portion of the raw material powder layer to which the binder is not supplied.

4. 4. The three-dimensional structure manufacturing device according to claim 1, further comprising a control unit that supplies the binder again to the raw material powder layer based on the captured image.

5. Let N be a natural number that does not include 0, the formation of the raw material powder layer, the supply of the binder to the raw material powder layer, and the photographing are repeatedly performed N times; an image analysis unit that analyzes the captured image obtained by the Nth capturing; a control unit that adjusts conditions for supplying the binder to the raw material powder layer for the (N+1)th time based on the analysis of the captured image; and The three-dimensional structure manufacturing apparatus according to any one of claims 1 to 3, comprising:

6. The raw material powder layers are stacked in multiple layers to form a laminate, the photographing means photographs a pattern of a portion where the binder is supplied in each of the raw material powder layers stacked in the multiple layers, The three-dimensional structure manufacturing device according to any one of claims 1 to 3, further comprising a three-dimensional model creation means for creating a three-dimensional model of the portion of the laminate to which the binder is supplied based on a photographed image of the pattern.

7. A layer of raw powder is formed on the stage. Supplying a liquid binder to the raw material powder layer; Photographing the portion of the raw material powder layer where the binder is supplied The process includes the steps of: A method for manufacturing a three-dimensional structure, wherein the liquid binder contains a coloring material for distinguishing between areas in the raw material powder layer to which the binder has been supplied and areas to which the binder has not been supplied in the captured image obtained by photographing.

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