Lamination planning apparatus, lamination molding system, and lamination planning method

Abstract

To easily suppress burn-through of a molten part when forming an object by laminating weld beads.SOLUTION: The control device (lamination planning device) drafts a lamination plan for building an object by laminating weld beads. The control device includes an acquisition unit configured to acquire three dimensional shape data of the object, and a path planning unit configured to plan a path that is a movement path of a melting unit for shaping the object. The path planning unit generates a plurality of path candidates each capable of shaping the object based on the shape data, sets, for each path candidate, a score that is an index representing a heat quantity of a base portion in contact with the melted portion in a process of moving the melted portion along each path candidate, and sets a path candidate having a minimum score as a path.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a stacking planning device, an additive manufacturing system, and a stacking planning method for an object to be manufactured by stacking weld beads. [Background technology]

[0002] For example, Japanese Patent No. 6997044 (Patent Document 1) discloses a lamination planning method for an object to be manufactured by laminating weld beads formed by melting and solidifying a filler metal. This lamination planning method sets the lamination direction of the weld beads using three-dimensional shape data of the object to be manufactured, places the base material at a neutral position in the lamination direction that minimizes thermal shrinkage of the entire object, and creates a lamination plan to build the object by laminating weld beads on both the front and back sides of the base material. As a result, in the object manufactured according to the lamination plan, thermal shrinkage is distributed in a balanced manner to both the front and back regions of the base material, thereby suppressing uneven thermal shrinkage of the entire object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6997044 Summary of the Invention [Problem to be solved by the invention]

[0004] The lamination planning method disclosed in Japanese Patent No. 6997044 (Patent Document 1) suppresses uneven thermal shrinkage of the entire object as described above, but there is a concern that the shape of each layer of the weld bead may not be stable. For example, if the base portion (base material or the portion of the weld bead already layered) that the molten part comes into contact with during lamination is hot, the molten part may melt through instead of solidifying properly due to the heat of the base portion, resulting in the height of the weld bead (the dimension in the lamination direction) being lower than planned. The lamination planning method disclosed in Japanese Patent No. 6997044 (Patent Document 1) does not take into account the temperature of the base portion that the molten part comes into contact with, so there is a possibility that the molten part may burn through, resulting in an unstable shape of the weld bead.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to make it easier to suppress burn-through of the molten part when forming an object by stacking weld beads. [Means for solving the problem]

[0006] A stacking planning device according to the present disclosure is a stacking planning device that creates a stacking plan for building an object by stacking weld beads, and includes an acquisition unit that acquires three-dimensional shape data of the object, and a path planning unit that plans a path that is a movement route of a molten part to build the object. The path planning unit generates a plurality of path candidates, each of which can build the object based on the shape data, sets a score for each path candidate that is an index representing the heat amount of a base part that comes into contact with the molten part in the process of moving the molten part along each path candidate, and sets the path candidate with the smallest score as the path.

[0007] An additive manufacturing system according to the present disclosure includes the above-described stacking planning device and a manufacturing device that manufactures an object by stacking weld beads in accordance with the stacking plan formulated by the stacking planning device.

[0008] A lamination planning method according to the present disclosure is a lamination planning method for creating a lamination plan for building an object by stacking weld beads, and includes the steps of acquiring three-dimensional shape data of the object and setting a path, which is a movement path of a molten part for building the object. The path setting step includes the steps of generating a plurality of path candidates, each of which can build the object based on the shape data, calculating, for each path candidate, a score representing the heat amount of a base portion with which the molten part comes into contact in the process of moving the molten part along each path candidate, and setting the path candidate with the smallest score as the path. [Effects of the Invention]

[0009] According to the present disclosure, when forming an object by stacking weld beads, it is possible to easily prevent the molten portion from burning through. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of an additive manufacturing system including a stacking planning device. [Figure 2] 1A and 1B are diagrams illustrating an example of a top view and a side view of an object formed in a rectangular shape on a base material. [Figure 3] FIG. 2 is a block diagram schematically showing functions related to stacking planning of the control device. [Figure 4] FIG. 10 is a diagram schematically illustrating an example of a method for creating a graph showing a layered region of an object. [Figure 5] FIG. 10 is a diagram illustrating a process of generating path candidates through a search process. [Figure 6] FIG. 6 is a diagram showing an example of score setting for path candidate A shown in FIG. 5. [Figure 7] FIG. 10 is a diagram illustrating an example of path setting. [Figure 8] 10 is a flowchart illustrating an example of a processing procedure executed by a path planning unit when setting a path. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0012] 1 is a diagram schematically illustrating an example of the configuration of an additive manufacturing system 1 equipped with a layering planning device according to this embodiment. The additive manufacturing system 1 is configured to manufacture an object 100 by layering weld beads 70. The additive manufacturing system 1 includes a welding power supply 10, a welding torch 20, a robot arm 40, a wire feeder 50, and a control device 30.

[0013] Robot arm 40 is a multi-joint arm, for example a six-axis multi-joint arm. Welding torch 20 is fixed to the tip of robot arm 40. Robot arm 40 functions as a moving device that moves welding torch 20 at a set welding speed. As robot arm 40 moves welding torch 20, weld beads 70 are formed by melting and fixing consumable electrode wire 51 (hereinafter also simply referred to as "wire 51"), and are laid up. Robot arm 40 is controlled by control device 30 so that object 100 is formed by laying up weld beads 70.

[0014] A welding current is supplied to wire 51 from a power feed tip (not shown) located inside nozzle 21 of welding torch 20. Wire 51 is melted by arc 22 generated between wire 51 and base metal 80 or already-laid weld bead 70. Arc 22 melts base metal 80 or already-laid weld bead 70 simultaneously with wire 51, forming molten zone (molten pool) 23, which cools and solidifies to form weld bead 70. Hereinafter, the lamination direction of weld bead 70 (the normal direction of base metal 80) will be referred to as the Z-axis direction, a direction perpendicular to the Z-axis direction (the longitudinal direction of base metal 80 in the example shown in FIG. 1) will be referred to as the X-axis direction, and a direction perpendicular to the Z-axis direction and the X-axis direction will be referred to as the Y-axis direction.

[0015] Welding power supply 10 supplies a welding current to wire 51. The welding current may be either direct current or alternating current.

[0016] Wire feeder 50 includes a roller and a motor (not shown). Wire feeder 50 feeds wire 51 to welding torch 20 by driving the motor to rotate the roller.

[0017] The control device 30 includes a CPU (Central Processing Unit), a memory, and an input / output port for inputting and outputting various signals (none of which are shown). These elements are connected via a bus.

[0018] Control device 30 controls robot arm 40, wire feeder 50, and welding power supply 10 in accordance with a stacking plan for building object 100. As a result, weld beads 70 are stacked in accordance with the stacking plan to build object 100. Control for realizing the functions of control device 30 may be processed by software or dedicated hardware (electronic circuitry). Note that while FIG. 1 illustrates an example of a configuration in which a command to wire feeder 50 is output from control device 30, a configuration in which a command to wire feeder 50 is output from welding power supply 10 rather than from control device 30 may also be used.

[0019] [Lamination planning] Control device 30 according to the present embodiment has a function of planning a lamination plan in addition to a function of laminating weld beads 70 according to the lamination plan. Specifically, control device 30 acquires three-dimensional shape data of target object 100 from the outside, and sets a movement path (hereinafter also referred to as a "path") of molten portion 23 for forming target object 100 based on the acquired shape data.

[0020] To form object 100 according to the lamination plan, it is desirable to stabilize the shape of each layer of weld bead 70. However, if the temperature of the base portion (base material 80 or the portion of weld bead 70 already laminated) that contacts molten portion 23 during lamination is excessively high, molten portion 23 may not solidify properly due to the heat from the base portion and may melt away. If such a melt-through of molten portion 23 occurs, the height (dimension in the Z-axis direction) of weld bead 70 will be lower than planned, and the shape of weld bead 70 will become unstable.

[0021] Fig. 2 shows an example of a bird's-eye view and a side view of an object formed in a rectangular shape on a base material. The object shown in Fig. 2 was formed by performing the operation of moving the molten zone in the X-axis direction to form linear weld beads extending in the X-axis direction multiple times while moving the start position of each weld bead by the width of the weld bead from the negative direction to the positive direction in the Y-axis direction.

[0022] As shown in FIG. 2, the base portion of the first weld bead is at a low temperature because no weld bead has yet been formed on the base material. Therefore, no burn-through occurs in the first weld bead. The base portion of the second weld bead is at a high temperature due to the heat from the first weld bead and its base portion. Therefore, the second weld bead is more likely to burn-through. The third and subsequent weld beads are even more likely to burn-through due to the heat from the weld beads formed up to that point and their base portions. In this way, when forming an object using weld beads, the heat from the base portion that comes into contact with the molten portion 23 during lamination makes it more likely that the molten portion will burn-through.

[0023] In view of this, when creating a lamination plan for the object 100, the control device 30 according to this embodiment sets a pass that makes it difficult for the melted portion 23 to burn through.

[0024] 3 is a block diagram showing functions related to stacking planning of the control device 30. The control device 30 has a shape data acquisition unit 31, a path planning unit 32, and a stacking command unit 33.

[0025] The shape data acquisition unit 31 communicates with the outside via wire or wirelessly to acquire from the outside three-dimensional shape data of the target object 100 to be manufactured.

[0026] The path planning unit 32 plans a path for forming the object 100 based on shape data of the object 100. The path planning unit 32 includes a path candidate generating unit 32a, a score setting unit 32b, and a path setting unit 32c.

[0027] The path candidate generating unit 32a generates a plurality of path candidates, each of which is capable of forming the object 100, based on the shape data of the object 100. For example, the path candidate generating unit 32a generates a plurality of path candidates using the following method.

[0028] First, path candidate generating unit 32a identifies the layered region of object 100 based on the shape data of object 100. Then, path candidate generating unit 32a defines the layered region of object 100 as a collection of multiple cells separated into a mesh shape by the width of weld bead 70, and creates a graph connecting the centers of the multiple cells.

[0029] Fig. 4 is a diagram schematically showing an example of a method for creating a graph showing the layered region of the object 100. Note that, although Fig. 4 simply shows the layered region of the object 100 in two dimensions, the actual layered region of the object 100 is three-dimensional.

[0030] Path candidate generation unit 32a grasps the layered region of object 100 as shown in Fig. 4(A) based on the shape data of object 100. Next, as shown in Fig. 4(B), path candidate generation unit 32a defines the layered region of object 100 as a collection of multiple cells separated into a mesh by the width of weld bead 70, and creates a graph in which the center of each of the multiple cells is a node and adjacent nodes are connected by edges.

[0031] When a graph is created, the path candidate generation unit 32a performs a division determination to determine whether or not to divide the created graph. Specifically, the path candidate generation unit 32a checks whether or not the created graph can be drawn in one stroke. If the created graph can be drawn in one stroke, the path candidate generation unit 32a maintains the created graph as is without dividing it. On the other hand, if the created graph cannot be drawn in one stroke, the path candidate generation unit 32a divides the created graph into multiple graphs (subgraphs), each of which can be drawn in one stroke. This division determination determines at least one graph that can be drawn in one stroke.

[0032] Whether a graph can be drawn in one stroke or not can be determined by known graph theory. Specifically, the number of edges connected to each node in the graph is calculated as the degree, and if the number of nodes with an odd degree is 0 (Eulerian graph) or 2 (quasi-Eulerian graph), the graph can be determined to be drawable in one stroke.

[0033] When the graphs are determined by the above-mentioned division determination, the path candidate generating unit 32a performs a search process to generate path candidates for each graph. In the search process, paths that can pass through all the nodes of the graph by moving the molten part at a constant movement speed (welding speed) are generated as path candidates.

[0034] Figure 5 is a diagram that shows a schematic diagram of the process of generating path candidates through search processing. Note that for the sake of simplicity, Figure 5 shows a two-dimensional graph with three nodes vertically and four nodes horizontally, but the actual graph is a more complex three-dimensional graph.

[0035] First, an initial graph is created at time t0, just before welding begins. Next, one of the multiple nodes contained in the graph is selected as the starting point. The starting point is the position of the molten part at time t1, when lamination begins. Below, the cell containing the starting point is also referred to as the "starting cell." If the initial graph is an Eulerian graph, it can be drawn in one stroke starting from any node, so any node is selected as the starting point. If the initial graph is a quasi-Eulerian graph, it can be drawn in one stroke starting from either node with an odd degree, so either node with an odd degree is selected as the starting point. The starting point is saved in a list of path candidates.

[0036] Once the starting point is selected, the node at the next time t2 is selected from among the nodes adjacent to the starting point, and the position of the molten part is moved to the next node. At this time, the node after the movement is registered in a list of path candidates, and the previous node is deleted from the graph. This series of processes of moving the molten part, registering it in the list, and deleting the node from the graph is repeated. A path that allows the molten part to pass through all nodes is a path that can be drawn in one stroke, and becomes a path candidate. Note that if the molten part cannot move to the next node, a path that can be drawn in one stroke is searched for by retracing the path and proceeding to another node until another node can be selected (so-called backtracking). Note that a path that can be drawn in one stroke may also be searched for by solving an optimization problem (such as the traveling salesman problem).

[0037] Note that FIG. 5 shows an example in which path candidate A is generated, which allows the molten part to pass through all nodes, by moving the molten part at a constant moving speed (welding speed) from time t1 to time t12.

[0038] As described above, in the search process, the path candidate generator 32a starts the movement of the molten part from a starting point (the center of the starting cell) among the multiple cells and searches for a route through which the molten part passes through the nodes of all the cells. Then, the path candidate generator 32a generates multiple path candidates by repeating this search process multiple times while changing the starting cell and the route.

[0039] Returning to Fig. 3, the score setting unit 32b will be described. When multiple path candidates are generated by the path candidate generating unit 32a, the score setting unit 32b sets a score for each of the multiple generated path candidates. The score is an index representing the amount of heat of cells in the base portion that come into contact with the molten part in the process of moving the molten part along each path candidate (hereinafter also referred to as "contact cells").

[0040] The score setting unit 32b sets a cost for the cells of the base portion that are not in contact with the molten part (hereinafter also referred to as "non-contact cells") each time the molten part is moved to an adjacent cell along each path candidate. The cost is an index representing the temperature of the non-contact cells.

[0041] The score setting unit 32b reduces the cost of the non-contact cell by 1 each time the molten part is moved to the next adjacent cell along each path candidate (i.e., each time the time for moving the molten part to the next cell has elapsed). This reduces the cost of the non-contact cell in response to the temperature decrease due to heat dissipation over time.

[0042] Furthermore, the score setting unit 32b increases the cost of the non-contact cells that are close to the contact cell by "5." This is to increase the cost of the cells close to the contact cell in response to the temperature rise of the cells close to the contact cell due to the heat transmitted from the contact cell to the surrounding area. This allows for a simple calculation of the heat transmission from the molten part.

[0043] Then, the score setting unit 32b stores the cost of the abutting cell each time the molten part is moved to the next cell along each path candidate, and sets the total value of the multiple costs stored until the molten part has passed through all the cells of each path candidate as the score of each path candidate.

[0044] Fig. 6 is a diagram showing an example of score setting for path candidate A shown in Fig. 5. Fig. 6 shows an example in which, among the cells in the base part, cells located vertically or horizontally of the adjacent cell are set as cells adjacent to the adjacent cell.

[0045] As shown in FIG. 6, the score setting unit 32b first sets the initial costs of all cells in the base portion at time t0, immediately before the start of welding. Note that FIG. 6 shows an example in which the initial cost is set to "0." Thereafter, the score setting unit 32b decreases the cost of non-contact cells (cells other than the abutting cells) by "1" each time the molten part is moved to the next cell along path candidate A. Note that FIG. 6 shows an example in which the lower limit of the cost is set to "0." Furthermore, the score setting unit 32b increases the cost by "5" for non-contact cells that are adjacent to the abutting cells (cells located vertically or horizontally of the abutting cells).

[0046] Then, the score setting unit 32b stores the cost of the abutting cell at that time each time the molten part moves to the next cell along the path candidate A. Then, the score setting unit 32b sets the score of the path candidate A to the total value of the multiple costs stored until the molten part passes through all the cells of the path candidate A.

[0047] To simplify the explanation, Figure 6 shows an example in which a cost is assigned only to the base portion that exists at time t0 immediately before the start of welding, and as a result, the final score of path candidate A is "65." However, in reality, the cells that the molten part has passed through after time t1 (the cells that make up path candidate A) also become base portions and are assigned costs, so the actual score of path candidate A is expected to be higher than "65."

[0048] The score setting unit 32b sets a score for each of the multiple path candidates generated by the path candidate generating unit 32a.

[0049] Returning to Fig. 3, the path setting unit 32c will be described. The path setting unit 32c sets the path candidate having the smallest score set by the score setting unit 32b as the official path from among the plurality of path candidates generated by the path candidate generating unit 32a.

[0050] Fig. 7 is a diagram showing an example of path setting. As shown in Fig. 7, when three path candidates A to C are generated and the scores of the three path candidates A to C are "65", "63", and "66", respectively, path candidate B with the smallest score is set as the official path.

[0051] Returning to Fig. 3, stacking command unit 33 will now be described. Stacking command unit 33 controls robot arm 40, wire feeder 50, and welding power supply 10 so as to move weld zone 23 along the path set by path setting unit 32c and stack weld beads 70. In this way, object 100 planned in the stacking plan is formed by stacking weld beads 70.

[0052] FIG. 8 is a flowchart showing an example of a processing procedure executed by the path planning unit 32 when setting up a path.

[0053] First, as shown in FIG. 4 above, the path planning unit 32 grasps the layered area of ​​the object based on the shape data of the object, and divides the grasped layered area into a mesh by the weld bead width to create a graph (step S10).

[0054] Next, the path planning unit 32 generates a plurality of path candidates using graph theory, as shown in FIG. 5 above (step S11).

[0055] Next, the path planning unit 32 selects a path candidate for which a score has not yet been assigned from among the multiple path candidates (step S20), and assigns a score to the selected path candidate (steps S21 to S26). Specifically, as shown in FIG. 6 above, the path planning unit 32 assigns an initial score to the cell of the base portion (step S21), moves the molten part to the next cell (step S22), stores the cost of the abutting cell (step S23), and assigns the cost of the non-abutting cell (step S24). This series of processes is repeated until the movement of the molten part is completed (NO in step S25), and when the movement of the molten part is completed (YES in step S25), the total of the multiple costs assigned until the movement is completed is assigned to the score of the path candidate (step S26).

[0056] If the scores of all the path candidates have not been set (NO in step S27), the path planning unit 32 repeats the processes of steps S20 to S26 until the scores of all the path candidates have been set.

[0057] When the scores of all the path candidates are set (YES in step S27), the path planning unit 32 sets the path candidate with the smallest score as the official path (step S30). As described above, the control device 30 according to this embodiment includes a shape data acquisition unit 31 that acquires three-dimensional shape data of an object, and a path planning unit 32 that plans a path, which is a movement path of the molten part for forming the object. The path planning unit 32 generates multiple path candidates based on the shape data of the object, assigns a score to each path candidate that is an index representing the heat amount of the base portion that the molten part contacts as the molten part moves along each path candidate, and sets the path candidate with the smallest score as the path. As a result, of the multiple path candidates, the path candidate with the smallest heat amount of the base portion that the molten part contacts is set as the official path. As a result, it is possible to more easily suppress burn-through of the molten part when forming an object by stacking weld beads.

[0058] Furthermore, the path planning unit 32 defines the stacking region of the object as an aggregate of multiple cells, generates multiple path candidates each passing through the centers of all cells, stores the cost of the abutting cells and sets the cost of non-abutting cells each time the molten part moves to the next cell along each path candidate, and sets the total value of the multiple costs stored until the molten part has moved through all the cells of each path candidate as the score for each path candidate. This makes it possible to set a path that is less likely to cause burn-through of the molten part, taking into account the temperature of the base part, which changes from moment to moment as the molten part moves.

[0059] Furthermore, each time the molten part is moved to the next cell along each path candidate, the path planning unit 32 decreases the cost of the non-contact cell by "1" and increases the cost of the non-contact cell that is adjacent to the abutting cell by "5." This makes it possible to appropriately set the cost of the non-contact cell, taking into account the temperature decrease due to heat radiation over time and the temperature increase due to heat propagated from the molten part.

[0060] Furthermore, control device 30 according to the present embodiment includes stacking command unit 33 that moves fusion zone 23 along the path set by path setting unit 32c to stack weld bead 70. This makes it possible to form an object with a stable weld bead shape.

[0061] [Variations] (A) In the above-described embodiment, the cost of a cell is set as a linear function of time t (the cost of a cell is decreased by "1" as time passes), but the cost of a cell may also be set as an nth-order function of time t (n is an integer greater than or equal to 2) or a function of a multidimensional variable that includes variables other than time t.

[0062] (B) When setting the cost of a cell, taking into account defects caused by excessive temperature drops, the cost of cells that have been stacked for a certain amount of time can be set to zero or a negative value. This allows for a path that passes through the base part that has been stacked for a certain amount of time to be set more quickly.

[0063] (C) The cost increase / decrease amount may be a variable value instead of a fixed value, which makes it easier to optimize the cost.

[0064] (D) The cost of the cell may be increased as the number of times the molten parts approach each other increases.

[0065] (E) In view of the fact that heat tends to accumulate more easily when layers are stacked in the weld bead, the cost of the cell may be increased as the weld bead layer becomes higher.

[0066] (F) When the welding current is AC, the higher the EN ratio, the lower the net heat input to the molten part. Therefore, the higher the EN ratio, the lower the cost. The EN ratio is the ratio of the time during which the wire is negative polarity to the total time in one AC cycle. Alternatively, the EN ratio may be the ratio of the time-integrated value of the negative polarity current in one AC cycle to the time-integrated value of the current in one AC cycle (the sum of the time-integrated value of the positive polarity current and the time-integrated value of the negative polarity current).

[0067] (G) The temperature may be actually monitored during lamination, and the cost may be changed based on the results.

[0068] (H) The cost may be changed during one layering. For example, the cost may be reduced near the starting point.

[0069] (I) The range of cells whose costs are to be increased may be changed. For example, the costs of cells located diagonally from the abutting cell, or cells located within a predetermined distance from the abutting cell, may be increased in addition to the cells located vertically or horizontally from the abutting cell.

[0070] (J) The cost may be derived using actually measured temperatures or temperature simulation values.

[0071] (K) In the above embodiment, the total value of the multiple costs stored until the fusion section passes through all the cells of each path candidate is set as the score for each path candidate. However, it is also possible to set the maximum value of the multiple costs stored until the fusion section passes through all the cells of each path candidate as the score for each path candidate.

[0072] (L) In the above embodiment, the cost is used only to calculate the final score, but when selecting a node, it is also possible to select a node that has the smallest cost.

[0073] (M) The width of the mesh (cell width) that separates the layered area of ​​the object is set to the width of the weld bead, but since the width of the weld bead can vary depending on the layering conditions, the mesh width may be varied depending on the layering conditions.

[0074] (N) In the layer immediately below the fusion zone where the cost fluctuations are large, the mesh size may be made finer.

[0075] (O) In areas where there is a large temperature gradient, such as where heat has accumulated, the mesh size may be made finer.

[0076] (P) In areas where heat conduction is likely to occur, the mesh size may be made finer.

[0077] (Q) If multiple bead widths can be set in welding power supply 10, the maximum bead width that can be drawn in one stroke may be selected from the settable bead widths.

[0078] (R) For example, if the number of paths varies depending on the bead width, you can select a bead width that results in fewer paths. For example, if the graph of the buildup area is not drawn in one stroke when the bead width is 6 mm (there will be two or more paths), but the graph of the buildup area can be drawn in one stroke when the bead width is 5 mm (there will be one path), you can set the bead width to 5 mm, which results in fewer paths.

[0079] (S) The shape of the cells separating the stacked regions does not have to be rectangular, and may be a shape other than rectangular, such as a triangle.

[0080] [Aspect] It will be understood by those skilled in the art that the above-described embodiments and their modifications are specific examples of the following aspects.

[0081] (Item 1) A stacking planning device according to the present disclosure creates a stacking plan for building an object by stacking weld beads, and includes an acquisition unit that acquires three-dimensional shape data of the object, and a path planning unit that plans a path, which is a movement route of a molten part for building the object. The path planning unit generates a plurality of path candidates, each of which can build the object based on the shape data, and assigns a score to each path candidate, which is an index representing the heat amount of a base portion that comes into contact with the molten part in the process of moving the molten part along each path candidate, and assigns the path candidate with the smallest score as the path.

[0082] According to the lamination planning device of the first paragraph, the path candidate that minimizes the heat quantity of the base portion in contact with the molten part is set as the official path among a plurality of path candidates. As a result, when building an object by stacking weld beads, it is possible to easily suppress burn-through of the molten part.

[0083] (Item 2) In the stacking planning device described in Item 1, the path planning unit defines the stacking area of ​​the object grasped based on the shape data as a collection of multiple cells divided into a mesh by the width of the weld bead, and generates multiple path candidates by repeating a search process multiple times while changing the starting cell and the path, in which the movement of the molten part starts from the center of a starting cell among the multiple cells and searches for a path through the centers of all cells for the molten part, and each time the molten part is moved to the next cell along each path candidate, stores the cost of the abutting cells, which are cells of the base part that the molten part abuts, and sets the cost of the non-abutting cells, which are cells of the base part that the molten part does not abut, and sets a score for each path candidate based on the multiple costs stored until the molten part has moved through all the cells of each path candidate.

[0084] (Item 3) In the stacking planning device described in item 2, the path planning unit sets the total or maximum value of the multiple costs as the score of each path candidate.

[0085] According to the lamination planning device of the second and third aspects, it is possible to set a path that is less likely to cause burn-through of the molten part, taking into consideration the temperature of the base part that changes from moment to moment due to the movement of the molten part.

[0086] (4) In the stacking planning device described in 3, the path planning unit reduces the cost of non-contact cells and increases the cost of cells that are close to the contact cells among the non-contact cells each time the molten part is moved to the next cell along each path candidate.

[0087] According to the lamination planning device of the fourth aspect, the cost of non-contacting cells can be appropriately set by taking into consideration the temperature decrease due to heat radiation over time and the temperature increase due to heat propagated from the molten portion.

[0088] (Item 5) An additive manufacturing system according to the present disclosure includes a stacking planning device according to any one of items 1 to 4, and a manufacturing device that manufactures an object by stacking weld beads in accordance with the stacking plan formulated by the stacking planning device.

[0089] According to the lamination planning device of the fifth aspect, an object with a stable weld bead shape can be manufactured.

[0090] (Item 6) A stacking planning method according to the present disclosure is a stacking planning method for creating a stacking plan for building an object by stacking weld beads, and includes the steps of acquiring three-dimensional shape data of the object and setting a path, which is a movement path of a molten part for building the object. The path setting step includes the steps of generating a plurality of path candidates, each of which can build the object based on the shape data, calculating for each path candidate a score representing the heat quantity of a base portion with which the molten part comes into contact in the process of moving the molten part along each path candidate, and setting the path candidate with the smallest score as the path.

[0091] According to the lamination planning method of Section 6, the path candidate that minimizes the heat quantity of the base portion in contact with the molten part is set as the official path among multiple path candidates. As a result, it is possible to easily suppress burn-through of the molten part when building an object by laminating weld beads.

[0092] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0093] 1 Additive manufacturing system, 10 welding power supply, 20 welding torch, 21 nozzle, 22 arc, 23 molten part, 30 control device, 31 shape data acquisition unit, 32 path planning unit, 32a path candidate generation unit, 32b score setting unit, 32c path setting unit, 33 stacking command unit, 40 robot arm, 50 wire supply device, 51 consumable electrode wire, 70 weld bead, 80 base material, 100 object.

Claims

1. A stacking planning device that creates a stacking plan for building an object by stacking weld beads, an acquisition unit that acquires three-dimensional shape data of the object; a path planning unit that plans a path that is a movement path of a molten part for forming the object, The path planning unit generating a plurality of path candidates each capable of forming the object based on the shape data; a score is set for each of the path candidates, the score being an index representing the amount of heat of a base portion that comes into contact with the molten portion during the process of moving the molten portion along each of the path candidates; The stacking planning device sets the path candidate that has the smallest score as the path.

2. The path planning unit The layered region of the object grasped based on the shape data is defined as an aggregate of a plurality of cells separated in a mesh shape by the width of the weld bead; generating the plurality of path candidates by repeating a search process multiple times while changing the start cell and the path, in which movement of the molten part is started from the center of a start cell among the plurality of cells and a path through which the molten part passes the centers of all of the cells; Each time the molten part is moved to the next cell along each of the path candidates, a cost of an abutting cell, which is a cell of the base part with which the molten part is in contact, is stored, and a cost of a non-abutting cell, which is a cell of the base part with which the molten part is not in contact, is set; The stacking planning device according to claim 1 , wherein a score for each of the path candidates is set based on a plurality of the costs stored until the fusion portion moves through all the cells of each of the path candidates.

3. The stacking planning device according to claim 2 , wherein the path planning unit sets a score for each of the path candidates to a total value or a maximum value of the plurality of costs.

4. 4. The stacking planning device according to claim 3, wherein the path planning unit decreases a cost of the non-contact cells and increases a cost of a cell adjacent to the contact cell among the non-contact cells, each time the molten portion is moved to a next cell along each of the path candidates.

5. a stacking planning device according to any one of claims 1 to 4; and a modeling device that models the object by stacking the weld beads in accordance with the stacking plan created by the stacking planning device.

6. A stacking planning method for creating a stacking plan for building an object by stacking weld beads, comprising: acquiring three-dimensional shape data of the object; setting a path that is a movement path of a molten part for forming the object, The step of setting the path includes: generating a plurality of path candidates each capable of forming the object based on the shape data; calculating, for each of the path candidates, a score representing the amount of heat of a base portion that comes into contact with the molten portion during the process of moving the molten portion along each of the path candidates; and setting the path candidate with the smallest score as the path.

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