Additive manufacturing apparatus

Abstract

To control the position of a table with high accuracy and to improve lamination molding accuracy in a powder bed type lamination molding.SOLUTION: The additive manufacturing apparatus 1 includes a table 12 on which the powder material M is spread, a material supply mechanism 14 that supplies a preset weight of the powder material to the table, a drive mechanism 13 that supports the table and moves the table in the vertical direction, a support structure 16 that supports the drive mechanism and supports the table via the drive mechanism, and a control unit 17 that controls the vertical position of the table when the powder material is supplied to the table. The control unit 17 corrects the position of the table in the vertical direction when the powder material is supplied to the table based on the posture change of at least one of the drive mechanism 13 and the support structure 16 due to the weight of the powder material M spread on the table 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an additive manufacturing apparatus. [Background technology]

[0002] Additive manufacturing machines are known as devices that build three-dimensional objects by layering and hardening materials. There are various methods for additive manufacturing, one of which is powder bed additive manufacturing. In powder bed additive manufacturing, powder material is first spread on a table inside the machine to form a thin layer of powder material. Next, a beam such as a laser is irradiated at a desired position on the powder material to harden the powder material at that position. After the powder material has selectively hardened, more powder material is formed on top of that powder material and hardened by the beam. This process is repeated to create the object.

[0003] In powder bed additive manufacturing, powder material is layered sequentially on a table, and the thickness of the powder material layer increases as the layering progresses. Therefore, in additive manufacturing devices, the vertical position of the table is adjusted as the layering progresses. This adjustment of the table position is generally performed based on the thickness of the powder material layer. However, in additive manufacturing, the weight of the powder material loaded on the table increases as the layering progresses. Therefore, the weight of the powder material may cause the table position to deviate from the specified position. Since deviation of the table position from the specified position affects the accuracy of additive manufacturing, it is desirable to precisely adjust the table position.

[0004] An additive manufacturing apparatus is disclosed in, for example, Patent Document 1. In this additive manufacturing apparatus, the table is driven by a drive unit, which is controlled by a control unit. The control unit controls the drive unit to match the current load on the table based on factors such as the amount of material laid per layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-25762 Summary of the Invention [Problem to be solved by the invention]

[0006] The additive manufacturing device of Patent Document 1 controls the table position taking into account the load on the table, thereby improving the accuracy of table position control. However, even with this additive manufacturing device, the table position may still deviate from the target position. In additive manufacturing, the thickness of the powder material spread on the table in one supply is, for example, several tens of micrometers, so it is desirable to control the table position with higher accuracy. In particular, in additive manufacturing of large objects or multi-cavity additive manufacturing, a large amount of powder material is supplied onto the table, which increases the load on the table. As a result, the table position is likely to deviate from the target position.

[0007] An object of the present invention is to improve the accuracy of additive manufacturing by controlling the position of a table with high precision in powder bed additive manufacturing. [Means for solving the problem]

[0008] (1) The additive manufacturing apparatus of the present invention is an additive manufacturing apparatus that manufactures a model by powder bed additive manufacturing, in which a beam is irradiated onto powder material spread on a table to harden the powder material, and includes: a table on which the powder material is spread; a material supply mechanism that supplies a preset weight of the powder material to the table; a drive mechanism that supports the table and moves it vertically; a support structure that supports the drive mechanism and supports the table via the drive mechanism; and a control unit that controls the drive mechanism to move the table vertically in stages and controls the vertical position of the table when supplying the powder material to the table so that the powder material is sequentially stacked on the table by the material supply mechanism, and the control unit corrects the vertical position of the table when supplying the powder material to the table based on changes in the posture of at least one of the drive mechanism and the support structure due to the weight of the powder material spread on the table.

[0009] In the above-described additive manufacturing device, powder material is sequentially stacked on the table, and as the stacking progresses, the load on the table increases, causing a change in the attitude of at least one of the drive mechanism and support structure that support the table. When the attitude of the drive mechanism and support structure changes, the position of the table supported by them tends to deviate from the target position, making it difficult to control. However, because the control unit corrects the table position taking into account the change in attitude of at least one of the drive mechanism and support structure, the table position when supplying powder material to the table can match or approach the target position. Therefore, the above-described additive manufacturing device can achieve high-precision table position control and improve additive manufacturing accuracy.

[0010] (2) In the additive manufacturing device of (1) above, the control unit may control the table to be positioned at a target position when supplying the powder material based on a preset position command, and may correct the position command so as to reduce displacement of the table from the target position due to the weight of the powder material spread on the table.

[0011] In the additive manufacturing device described in (2) above, the table can be positioned at or near the target position before supplying the powder material because the table's displacement (deviation) from the target position is corrected in advance. This allows the powder material to be spread on the table and the beam to be irradiated onto the spread powder material with high precision, thereby improving the accuracy of additive manufacturing.

[0012] (3) In the additive manufacturing device of (2) above, the control unit may correct the position command based on a preset amount of displacement of the table from a target position due to a change in posture of at least one of the drive mechanism and the support structure.

[0013] As described above, in the above-mentioned additive manufacturing device, the weight of the powder material causes the attitude of at least one of the drive mechanism and the support structure to change, which results in the table position easily shifting from the target position. In contrast, in the additive manufacturing device described in (3) above, the relationship between the change in attitude of at least one of the drive mechanism and the support structure due to the weight of the powder material and the deviation of the table from the target position is determined in advance, and the table position is controlled based on this. Therefore, with the above-mentioned additive manufacturing device, the table position can be controlled with high precision, thereby improving the additive manufacturing accuracy.

[0014] (4) In the layered manufacturing apparatus of (2) above, the control unit may change the amount of correction of the position command depending on the number of times the powder material is supplied to the table.

[0015] The weight of the powder material loaded on the table increases as the processing progresses. In the additive manufacturing device described above in (4), the correction amount of the table position is changed as the processing progresses. Therefore, even in processing in which the weight of the powder material loaded on the table increases significantly, such as when powder material is supplied multiple times, the table position can be positioned at or close to the target position. Therefore, the additive manufacturing device described above can achieve high-precision table position control and improve additive manufacturing accuracy.

[0016] (5) In the additive manufacturing device of (1) above, the drive mechanism may be arranged horizontally offset from the table, extend in the vertical direction, and move and support the table between both ends in the vertical direction.

[0017] In the additive manufacturing device (5) above, the drive mechanism supporting the table extends in the vertical direction. In an additive manufacturing device configured in this manner, the drive mechanism is prone to tilting (flexing) due to the load on the table, making it easy for its posture to change. However, the control unit controls the position of the table by taking into account the deviation of the table from its target position due to the weight of the powder material. Therefore, with the additive manufacturing device described above, the accuracy of additive manufacturing can be improved even in a configuration in which the table is prone to deviation from its target position due to the weight of the powder material.

[0018] (6) In the additive manufacturing device of (5) above, the support structure may be provided adjacent to the drive mechanism and horizontally outward of the drive mechanism, and may support both ends of the drive mechanism.

[0019] In the additive manufacturing device (6) above, the support structure supports the drive mechanism, which extends vertically and thus is prone to change in position. Therefore, the position of the support structure is prone to change when the position of the drive mechanism changes. However, the control unit controls the position of the table, taking into account the deviation of the table from the target position due to the weight of the powder material. Therefore, with the additive manufacturing device described above, the accuracy of additive manufacturing can be improved even in a configuration in which the table is prone to deviation from the target position due to the weight of the powder material. [Effects of the Invention]

[0020] According to the layered manufacturing device of the present invention, in powder bed type layered manufacturing, it is possible to achieve high precision in table position control and improve layered manufacturing accuracy. [Brief explanation of the drawings]

[0021] [Figure 1]1 is a front view schematically showing the configuration of an additive manufacturing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a drive mechanism and its surrounding configuration. [Figure 3] 1A-1C are diagrams showing a schematic diagram of a process in which powder material is deposited on a table of an additive manufacturing apparatus. [Figure 4] FIG. 2 is a functional block diagram showing a control unit, a driving mechanism, and a material supply mechanism in the additive manufacturing apparatus of the present embodiment. [Figure 5] FIG. 10 is a diagram showing an information table describing the relationship between the powder material layered on the table, its weight, and the amount of change in posture of the drive mechanism and support structure. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] FIG. 1 is a front view schematically illustrating the configuration of an additive manufacturing apparatus according to this embodiment. The additive manufacturing apparatus 1 is an apparatus for performing additive manufacturing using a powder bed method. The additive manufacturing apparatus 1 includes a processing chamber 11 for performing additive manufacturing. The processing chamber 11 has a housing shape. A portion of the underside of the processing chamber 11 is formed by a table 12 for forming a molded object. The table 12 is configured to be movable in the vertical direction and is driven by a drive mechanism 13. The drive mechanism 13 is controlled by a control unit 17. A powder material is supplied onto the table 12 from a material supply mechanism 14, and a powder material M is formed. After one layer of powder material M is formed, a beam is irradiated from a beam head 15 onto any position on the powder material M, and the powder material at that position hardens. After the beam irradiation is completed, the table 12 is lowered by the drive mechanism 13, and a next layer of powder material M is formed on the previously formed powder material M, and the next layer of powder material M is irradiated with the beam. This process is repeated to form a three-dimensional object.

[0024] Here, the front of the additive manufacturing apparatus 1 refers to the side where a door for removing the molded object from the processing chamber 11 is provided. The direction from the back of the additive manufacturing apparatus 1 to the front is called the front, and the direction from the front to the back is called the back. When viewed from the front, the direction toward the left of the additive manufacturing apparatus 1 is called the left, and the direction toward the right is called the right. When viewed from the front, the direction toward the top (ceiling) of the additive manufacturing apparatus 1 is called the up, and the direction toward the bottom (floor) is called the down. The up-down direction refers to the direction that coincides with the vertical direction when the additive manufacturing apparatus 1 is placed. The horizontal direction refers to the direction included in a plane whose normal is the up-down direction. The configuration of the additive manufacturing apparatus 1 will be described in detail below.

[0025] The beam head 15 is provided outside the processing chamber 11 and irradiates the powder material M with a beam through an irradiation window provided in the processing chamber 11. The beam head 15 irradiates, for example, a laser beam. However, the beam head 15 may irradiate other beams such as an electron beam. The beam head 15 is configured to be able to irradiate the beam at any position on the powder material M spread on the table 12.

[0026] The table 12 is also referred to as a build platform, and powder material is piled up on it to form a molded object. The table 12 is configured to be movable below the bottom surface of the processing chamber 11. The table 12 moves downward as the powder material M is piled up. The shape of the table 12 is not particularly limited as long as it is capable of piling up the powder material M. A support 18 is provided on the bottom surface of the table 12. The support 18 has a cylindrical shape and extends downward from the bottom surface of the table 12. The support 18 is attached to a basket 19.

[0027] The basket 19 has a box shape. The basket 19 includes a bottom 191 to which a support column is attached, and sidewalls 192 extending upward from the bottom 191. The bottom 191 has a flat, plate-like shape and is provided horizontally. The sidewalls 192 extend upward from the left end of the bottom 191. The sidewalls 192 extend upward from the right end of the bottom 191. The sidewalls 192 may be provided at the front end or the rear end of the bottom 191. The basket 19 configured in this manner is attached to a drive mechanism 13. The drive mechanisms 13 are provided on both the left and right sides of the table 12.

[0028] 2 is an enlarged view of the drive mechanism and its surrounding configuration. Here, the drive mechanism provided on the left side of table 12 will be described, but the drive mechanism on the right side has a similar configuration. Drive mechanism 13 includes a ball screw 131, a slide portion 132 that moves along ball screw 131, a guide portion 133 that guides slide portion 132 so as to move in the vertical direction, and a drive device 134 that rotates ball screw 131. Note that drive mechanism 13 includes a position sensor (not shown), such as a linear encoder, to detect the vertical position of table 12.

[0029] The ball screw 131 is composed of a screw shaft 1311 and a ball nut 1312. The screw shaft 1311 is rotated around its central axis by a drive unit 134. The screw shaft 1311 extends in the vertical direction. Both ends of the screw shaft 1311 in the vertical direction are fixed to the support structure 16 via fixing members 1313. The fixing members 1313 include bearings and the like, and are configured to allow the screw shaft 1311 to rotate while immobilizing the screw shaft 1311 relative to the support structure 16. The ball nut 1312 moves in the vertical direction along the screw shaft 1311 as the screw shaft 1311 rotates. A slide portion 132 is attached to the ball nut 1312.

[0030] The side wall portion 192 of the basket 19 is attached to the slide portion 132. The slide portion 132 moves up and down together with the ball nut 1312. The slide portion 132 is inserted into the guide portion 133. The guide portion 133 extends up and down. The guide portion 133 restricts the slide portion 132 from rotating due to the rotation of the screw shaft 1311, and guides the slide portion 132 to move up and down. The guide portion 133 is attached to the support structure 16.

[0031] The support structure 16 is provided outside the table 12 and the drive mechanism 13. The support structures 16 are provided on both the left and right sides of the table 12. The support structure 16 is provided adjacent to the drive mechanism 13. The processing chamber 11 is provided on top of the support structure 16, and the support structure 16 supports the processing chamber 11. The support structure 16 forms a base that supports the processing chamber 11, the drive mechanism 13, and the table 12.

[0032] As described above, in the additive manufacturing apparatus 1, the table 12, the drive mechanism 13, and the support structure 16 are directly or indirectly connected. Therefore, the load applied to the table 12 is applied to the support structure 16 via the table 12 and the drive mechanism 13. In other words, the additive manufacturing apparatus 1 is configured such that the load of the powder material M stacked on the table 12 is applied to the drive mechanism 13 and the support structure 16. Therefore, the weight of the powder material loaded on the table 12 may cause the attitudes of the drive mechanism 13 and the support structure 16 to change. The change in attitude refers to the drive mechanism 13 and the support structure 16 being tilted or deformed by bending more than when no powder material is loaded on the table 12. For example, when the weight of the powder material is loaded on the table 12, an inward force is applied to the ball screw 131 and the guide unit 133, which may cause the attitudes of the ball screw 131 and the guide unit 133 to change. Furthermore, an inward force is also applied to the support structure 16 that supports the ball screw 131 and the guide part 133, which may change the posture of the support structure 16. As a result, the table 12 may deviate from the target position, which may affect the accuracy of additive manufacturing.

[0033] Therefore, in the additive manufacturing apparatus 1 of this embodiment, the position of the table 12 is controlled taking into consideration changes in the posture of the drive mechanism 13 and the support structure 16. This point will be described in detail below, but first, the control of the position of the table 12 when the weight of the powder material loaded on the table 12 is not taken into consideration will be described.

[0034] FIG. 3 is a diagram schematically illustrating the process of layering powder material on the table of an additive manufacturing device. The process proceeds in the order of (A) to (C) in the figure. Referring to (A) in the figure, first, the table 12, which is positioned on the same plane as the bottom surface of the processing chamber 11 as its initial position, is lowered so that it is positioned below the bottom surface of the processing chamber 11. The amount of downward movement of the table 12 is not particularly limited, but it corresponds to, for example, the thickness of the first layer of powder material M1 to be spread. In other words, the table 12 is moved to the target position P1 for spreading the first layer of powder material M1.

[0035] Referring to (B) in the figure, next, the material supply mechanism 14 moves horizontally under the processing chamber 11 and spreads the first layer of powder material M1 on the table 12. The material supply mechanism 14 spreads the powder material on the table 12, for example, by using a roller. Thereafter, the beam head 15 irradiates a beam at a predetermined position in accordance with the processing program to harden the powder material.

[0036] Referring to (C) in the figure, next, the table 12 is lowered to a target position P2 below the target position P1. The target position P2 is the position of the table 12 for spreading the second layer of powder material M2. At the target position P2, the powder material M1 on the table 12 is located below the bottom surface of the processing chamber 11. In this case, the amount of downward movement of the table 12 is not particularly limited, but may be, for example, equivalent to the thickness of the second layer of powder material M2 to be spread. Thereafter, as described above, the material supply mechanism 14 spreads new powder material M2 on top of the already spread powder material M1. Then, the beam emitted by the beam head 15 hardens the powder material at a predetermined position of the new powder material M2. The additive manufacturing apparatus 1 repeats this process to form a three-dimensional object.

[0037] However, in reality, the weight of the powder material is loaded onto the table 12, causing the attitudes of the drive mechanism 13 and the support structure 16 to change, causing the position of the table 12 to deviate from the target position. The deviation of the table 12 from the target position increases as the amount of powder material spread on the table 12 increases. Therefore, in the additive manufacturing apparatus 1 of this embodiment, the control unit 17 controls the position of the table 12 so as to reduce the deviation (displacement) of the table 12 from the target position.

[0038] 4 is a functional block diagram showing the control unit, drive mechanism, and material supply mechanism of the layered manufacturing apparatus of this embodiment. The control unit 17 is configured by a computer including a processor, memory, etc., and controls each unit of the layered manufacturing apparatus.

[0039] When a processing program for forming a molded object is executed by an external input or the like, the control unit 17 transmits a position command to the drive mechanism 13 to move the table 12 to a target position for spreading the first layer of powder material. Upon receiving the position command, the drive mechanism 13 moves the table 12 to the target position. The position of the table 12 is transmitted to the control unit 17 from a position sensor as position information.

[0040] When the control unit 17 determines that the table 12 has reached the target position based on information from the position sensor, it sends a material supply command to the material supply mechanism 14. Upon receiving the material supply command, the material supply mechanism 14 moves horizontally and spreads the powder material over the table 12. When the material supply mechanism 14 has finished spreading the powder material, it sends supply completion information to the control unit 17.

[0041] When control unit 17 receives the supply pipe amount information, it moves table 12 to the target position for spreading the powder material in the second layer. In this case, control unit 17 sends a corrected position command that corrects the position command sent to drive mechanism 13. The corrected position command is the amount of movement of table 12 from target position P1 for spreading the powder material in the first layer to target position P2 for spreading the powder material in the second layer, corrected by the amount of displacement of table 12 from target position P2 due to the weight of the powder material. The corrected position command is written in an information table stored in advance in the memory of control unit 17.

[0042] FIG. 5 is a diagram showing an information table describing the relationship between the powder material layered on the table, its weight, and the amount of change in posture of the drive mechanism and support structure. The information table describes weight information, which is the weight of each powder material layered on the table 12. For example, the weight information describes that the weight of the powder material L1 in the first layer is W1 and the weight of the powder material L2 in the second layer is W2. In this embodiment, all of the powder material layered on the table 12 has the same weight, but the weights of the powder material layers may be different. The information table also describes posture change information regarding the amount of change in posture of the drive mechanism 13 and the support structure 16 corresponding to the number of times (number of layers) the powder material is supplied. For example, when the second layer of powder material L2 is spread on the table 12, the table 12 is loaded with the total weight W1+W2 of the powder material layers in the first and second layers. Therefore, in this case, the posture change amount information describes the posture change amount C2 for each of the drive mechanism 13 and the support structure 16 when the total weight W1+W2 of the powder material for the first and second layers is loaded onto the table 12. In this case, the information table describes the displacement amount d2, which is the deviation from the target position of the table 12 when the posture change amount is C2 (i.e., the target position when the next, third layer of powder material is to be spread out with the weights of the powder material for the first and second layers loaded onto the table 12). When spreading the powder material for the third layer, the control unit 17 sends a corrected position command to the drive mechanism 13, correcting the movement amount to the target position by the displacement amount d2. The posture change amount described in the information table can be obtained in advance, for example, by numerical simulation.

[0043] In this way, in the additive manufacturing apparatus 1 of this embodiment, the position of the table 12 is controlled taking into account deviation of the table 12 from the target position due to the weight of the powder material sequentially piled up on the table 12. Therefore, when spreading the powder material and when irradiating the powder material with a beam, the table 12 is positioned at or near the target position. This maintains an appropriate distance between the powder material and the beam head 15, improving the accuracy of additive manufacturing.

[0044] Furthermore, in the additive manufacturing apparatus 1, the table 12, which moves in the vertical direction, is supported by drive mechanisms 13 that are provided on the left and right sides of the table 12 and extend in the vertical direction. In an additive manufacturing apparatus 1 configured in this manner, the drive mechanism 13 is prone to tilting (flexing) due to the load applied to the table 12, and its posture is prone to change. In other words, the weight of the powder material easily causes the table 12 to deviate from the target position. However, the control unit 17 controls the position of the table 12 by taking into account the deviation of the table 12 from the target position due to the weight of the powder material. Therefore, with the additive manufacturing apparatus 1, the accuracy of additive manufacturing is improved even in a configuration in which the table 12 is prone to deviating from the target position due to the weight of the powder material.

[0045] The above-described embodiments are illustrative in all respects and are not limiting. Modifications and variations are possible for those skilled in the art. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications from the embodiments within the scope of the claims and their equivalents.

[0046] For example, the correction of the position command sent to the drive mechanism may be performed every time the powder material is spread on the table, or may be performed after the powder material has been spread a predetermined number of times.

[0047] For example, in the above-described embodiment, the deviation of the table from the target position is calculated in advance based on changes in the posture of both the drive mechanism and the support structure, but the deviation of the table from the target position may also be calculated in advance based on changes in the posture of either the drive mechanism or the support structure. [Explanation of symbols]

[0048] 1: Additive manufacturing equipment 11: Processing room 12: Table 13: Drive mechanism 131: Ball screw 1311: Screw shaft 1312: Ball nut 1313: Fixing member 132: Slide section 133: Guide section 134: Drive unit 14: Material supply mechanism 15: Beam Head 16:Support structure 17: Control section 18: Strut 19: Basket 191: Bottom 192: Side wall M,M1,M2: Powder material P1,P2:Target position

Claims

1. 1. An additive manufacturing apparatus for manufacturing a model by powder bed additive manufacturing, in which a beam is irradiated onto a powder material spread on a table to harden the powder material, a table on which the powder material is spread; a material supply mechanism for supplying a preset weight of the powder material to the table; a drive mechanism that supports the table and moves it vertically; a support structure that supports the drive mechanism and supports the table via the drive mechanism; a control unit that controls the drive mechanism to move the table in a vertical direction in a stepwise manner, and controls the vertical position of the table when the powder material is supplied to the table by the material supply mechanism so that the powder material is sequentially piled up on the table, The control unit corrects the vertical position of the table when supplying the powder material to the table based on changes in posture of at least one of the drive mechanism and the support structure due to the weight of the powder material spread on the table.

2. The additive manufacturing apparatus according to claim 1, The control unit controls the table to be positioned at a target position when supplying the powder material based on a preset position command, and corrects the position command to reduce displacement of the table from the target position due to the weight of the powder material spread on the table.

3. The additive manufacturing apparatus according to claim 2, The control unit corrects the position command based on a preset amount of displacement from a target position of the table due to a change in posture of at least one of the drive mechanism and the support structure.

4. The additive manufacturing apparatus according to claim 2, The control unit changes a correction amount of the position command depending on the number of times the powder material is supplied to the table.

5. The additive manufacturing apparatus according to claim 1, The drive mechanism is disposed horizontally offset from the table, extends in the vertical direction, and moves and supports the table between both ends in the vertical direction.

6. The additive manufacturing apparatus according to claim 5, The support structure is arranged adjacent to the drive mechanism and horizontally outward of the drive mechanism, and supports both ends of the drive mechanism.

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