Control method for lamination molding device, control device for lamination molding device, and program

Abstract

A control method of a lamination molding device for molding a molded object by laminating weld beads using a welding torch includes the steps of: acquiring a planned value of the width of a gap to be formed by a plurality of weld beads, the planned value being acquired from a lamination plan related to a process for molding the molded object; measuring a plurality of shape profiles respectively corresponding to the plurality of weld beads laminated on the basis of the lamination plan; deriving the actual value of the width of the gap on the basis of the plurality of shape profiles; and correcting lamination conditions of the plurality of weld beads to reduce the amount of deviation between the planned value of the width of the gap and the actual value of the width of the gap.

Description

Method for controlling an additive manufacturing device, control device for an additive manufacturing device, and program

[0001] The present disclosure relates to a method for controlling an additive manufacturing apparatus, a control device for an additive manufacturing apparatus, and a program.

[0002] Patent Document 1 describes an automatic multi-layer welding apparatus that includes a first control means for detecting a weld bead width using an optical sensor, an arc voltage, or the like, and storing the results, and controlling welding conditions based on the weld bead width, and a second control means for detecting and storing the arc voltage during welding and controlling welding conditions based on the differential voltage from the arc voltage or a predetermined reference voltage, and that controls the welding conditions to achieve a predetermined bead stack height.

[0003] Japanese Patent Application Laid-Open No. 2000-033477

[0004] When manufacturing a structure in which multiple weld beads form gaps, if a configuration is adopted in which the stacking conditions are corrected solely from the perspective of the stacking height of the weld beads, it is not possible to keep the gap width within an appropriate range.

[0005] An object of the present disclosure is to keep the gap width within an appropriate range when manufacturing a shaped object in which multiple weld beads form gaps.

[0006] To this end, the present disclosure provides a control method for an additive manufacturing apparatus that builds a shaped object by stacking weld beads with a welding torch, the control method including the steps of: acquiring a planned value of a gap width formed by a plurality of weld beads from a stacking plan related to a process for building the shaped object; measuring a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; deriving an actual value of the gap width based on the plurality of shape profiles; and correcting stacking conditions for the plurality of weld beads so as to reduce a deviation between the planned value of the gap width and the actual value of the gap width. In the deriving step, the distance between specific positions of each of the plurality of shape profiles may be derived as the actual value of the gap width. In this case, the specific positions may be tip positions of each of the plurality of shape profiles protruding in the gap direction. In the deriving step, the tip positions of each of the plurality of weld beads protruding in the gap direction may be estimated from the specific positions of each of the plurality of shape profiles, and the distance between the tip positions may be derived as the actual value of the gap width. In this case, the specific position may be the tip position of each of the multiple shape profiles protruding in the gap direction. In the correcting step, the lamination conditions may be corrected using a correction formula in which at least one of a proportional term, a differential term, and an integral term corresponding to the deviation amount is added to standard set values ​​of the lamination conditions. In this case, in the correcting step, as the lamination progresses, a correction formula in which an integral term is not added to standard set values ​​of the lamination conditions may be switched to a correction formula in which an integral term is added to standard set values ​​of the lamination conditions. In the correcting step, a planned value of a target position when laminating each of the multiple weld beads of the next layer may be corrected to a specific position of each of the multiple shape profiles. In this case, the specific position may be a position where the planned value of the target position is extended in the lamination direction and intersects with each shape profile. In the correcting step, as the lamination progresses, a correction method for correcting the lamination conditions may be switched from a first correction method to a second correction method.The first correction method may be a method of correcting the lamination conditions so as to reduce a deviation between a planned value of the growth amount in the lamination direction of each of the plurality of weld beads and an actual value of the growth amount derived based on the shape profile, and the second correction method may be a method of correcting the lamination conditions so as to reduce a deviation between a planned value of the gap width and an actual value of the gap width.

[0007] The present disclosure also provides a control device for an additive manufacturing device that forms a structure by stacking weld beads with a welding torch, the control device including: an acquisition unit that acquires a planned value for the width of the gap formed by a plurality of weld beads from a stacking plan related to the process of forming the structure; a measurement unit that measures a plurality of shape profiles that respectively correspond to the plurality of weld beads stacked based on the stacking plan; a derivation unit that derives an actual value for the gap width based on the plurality of shape profiles; and a correction unit that corrects the stacking conditions of the plurality of weld beads so as to reduce the amount of deviation between the planned value for the gap width and the actual value for the gap width.

[0008] Furthermore, the present disclosure also provides a program for enabling a control device of an additive manufacturing device that forms a structure by stacking weld beads with a welding torch to achieve the following functions in the control device: acquiring a planned value for the width of the gap formed by a plurality of weld beads from a stacking plan related to the process of forming the structure; measuring a plurality of shape profiles corresponding to each of the plurality of weld beads stacked based on the stacking plan; deriving an actual value for the gap width based on the plurality of shape profiles; and correcting the stacking conditions of the plurality of weld beads so as to reduce the deviation between the planned value for the gap width and the actual value for the gap width.

[0009] According to the present disclosure, when manufacturing an object in which a plurality of weld beads form gaps, the width of the gaps can be kept within an appropriate range.

[0010] 1 is a diagram showing an example of a schematic configuration of a metal additive manufacturing system according to the present embodiment; FIG. 2 is a diagram showing an example of a hardware configuration of a control device according to the present embodiment; FIG. 3 is a diagram showing an overview of control by a control device according to a first embodiment; FIG. 4 is a diagram showing an example of a functional configuration of a lamination planning device according to the first embodiment; FIG. 5 is a diagram showing an example of a functional configuration of a control device according to the first embodiment; FIG. 6 is a diagram showing an example of a shape profile received by a shape profile receiving unit of the control device; FIG. 7 is a diagram showing a method of deriving a gap width and a target position by a gap width derivation unit of the control device; FIG. 8 is a flowchart showing an example of an operation of the lamination planning device according to the first embodiment; FIG. 9 is a flowchart showing the contents of a molding control process executed by the control device according to the first embodiment; FIG. 10 is a diagram showing an overview of other control by a control device according to a second embodiment; FIG. 11 is a diagram showing an example of a functional configuration of a control device according to the second embodiment;

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0012] 1 is a diagram showing an example of the schematic configuration of a metal additive manufacturing system 1 according to the present embodiment. As shown in the figure, the metal additive manufacturing system 1 includes a welding robot (manipulator) 10, a CAD device 20, a stacking planning device 30, and a control device 50. The stacking planning device 30 writes a control program for controlling the welding robot 10 to a removable recording medium 70 such as a memory card, and the control device 50 is capable of reading the control program written to the recording medium 70.

[0013] The welding robot 10 includes an arm 11 with multiple joints and performs welding operations by operating in accordance with a control program loaded by a control device 50. The welding robot 10 also has a welding torch 13 attached to the tip of the arm 11 via a wrist 12 for forming the additively manufactured object 100. In the case of the metal additive manufacturing system 1, the welding robot 10 moves the welding torch 13 while melting a mild steel filler material (wire) 14 to manufacture the additively manufactured object 100. Specifically, the welding torch 13 supplies the filler material 14 and generates an arc while flowing a shielding gas to melt and solidify the filler material 14, thereby stacking multiple layers of weld beads (hereinafter simply referred to as "beads") on the base material 90 to manufacture the additively manufactured object 100. Note that although an arc is used as a heat source for melting the filler material 14 here, a laser or plasma may also be used. The welding robot 10 also includes a feeder that feeds the filler material 14, but a description of this will be omitted. The welding robot 10 is an example of an additive manufacturing device that forms a shaped object by stacking weld beads using a welding torch.

[0014] The welding robot 10 also includes a shape measuring instrument 15 at the tip of the arm 11. The shape measuring instrument 15 measures the shape of the layered object 100 during layering by the welding robot 10. The shape measuring instrument 15 is preferably capable of acquiring a cross-sectional shape profile of the layered object 100. For example, a shape measuring sensor that acquires a cross-sectional shape profile based on the intensity of reflected light of irradiated laser light can be used as this shape measuring instrument 15. Alternatively, the shape measuring instrument 15 is not limited to this, and a device that can measure three-dimensional shapes may also be used. However, the following description will be given assuming that a device that acquires a cross-sectional shape profile based on the intensity of reflected light of irradiated laser light is used.

[0015] The CAD device 20 has a function of designing a model using a computer and storing three-dimensional data obtained by the design (hereinafter referred to as "three-dimensional CAD data").

[0016] The stacking planning device 30 creates a stacking plan for the layered object 100 based on the three-dimensional CAD data held by the CAD device 20. That is, the stacking planning device 30 determines the trajectory of the welding torch 13 and also determines the welding conditions for welding by the welding robot 10. Then, the stacking planning device 30 generates a control program for controlling the welding robot 10 so as to form a bead along the determined trajectory under the determined welding conditions, and outputs this control program to the recording medium 70.

[0017] The control device 50 reads and stores a control program from the recording medium 70. The control device 50 then operates this control program to control the welding robot 10 in accordance with the stacking plan created by the stacking planning device 30, that is, to form a bead along the trajectory determined by the stacking planning device 30 under the welding conditions determined by the stacking planning device 30. The control device 50 is an example of a control device for an additive manufacturing device.

[0018] [Hardware Configuration of Control Device] FIG. 2 is a diagram illustrating an example of the hardware configuration of the control device 50. As illustrated, the control device 50 is realized, for example, by a general-purpose personal computer (PC) or the like, and includes a CPU 51 serving as a computing unit, a main memory 52 serving as a storage unit, and a magnetic disk drive (HDD: Hard Disk Drive) 53. The CPU 51 executes various programs, such as an operating system (OS) and application software, to realize the various functions of the control device 50. The main memory 52 is a storage area for storing various programs and data used for executing the programs, and the HDD 53 is a storage area for storing input data for the various programs and output data from the various programs. The control device 50 also includes a communication I / F 54 for communicating with the outside, a display mechanism 55 including a video memory and a display, input devices 56 such as a keyboard and a mouse, and a driver 57 for reading and writing data from and to a recording medium 70. It should be noted that FIG. 2 merely illustrates an example of a hardware configuration in which the control device 50 is realized by a computer system, and the control device 50 is not limited to the configuration shown in the figure.

[0019] 2 can also be regarded as the hardware configuration of the stacking planning device 30. However, when describing the stacking planning device 30, the CPU 51, main memory 52, magnetic disk device 53, communication I / F 54, display mechanism 55, input device 56, and driver 57 in FIG. 2 will be expressed as CPU 31, main memory 32, magnetic disk device 33, communication I / F 34, display mechanism 35, input device 36, and driver 37, respectively.

[0020] [Background and Overview of the Present Embodiment] In the metal additive manufacturing system 1, the control device 50 controls the welding robot 10 to perform additive welding based on a lamination plan created by the lamination planning device 30. However, even when additive welding is performed based on this lamination plan, the amount of deposited material is not constant each time and deviates from the plan due to individual differences in the welding power source and device, slight diameter differences depending on the lot of the filler material 14, and the like. For example, consider a case in which a hollow flow path is additively manufactured from the left and right to form left and right additively manufactured objects 100, and finally, these left and right additively manufactured objects 100 are closed to complete the product. In this case, if the gap width between the left and right additively manufactured objects 100 exceeds the standard range, various problems occur, such as burn-through, a lack of back waves, insufficient penetration, and insufficient strength.

[0021] In this embodiment, for an additively formed object 100 such as a flow channel having a hollow shape formed by stacking beads symmetrically on both sides, the gap width is controlled to fall within a target numerical range in order to perform a closure weld with a back bead in the final welding process stably and without defects.

[0022] In this embodiment, the layering of the layered object 100 will be described using an example of lamination of a channel having a circular arch-shaped cross section, but this is not limited thereto. This embodiment is widely applicable to lamination of objects having other cross-sectional shapes, such as square pipes, or structures with specified spacing between shapes. In other words, this embodiment is applicable to layered objects 100 in which two independent beads form a gap. Alternatively, the number of independent beads does not have to be two, and this embodiment can also be said to be applicable to layered objects 100 in which multiple independent beads form a gap. In the following description, the layered object 100 will be described as consisting of n layers.

[0023] 3 is a diagram showing an outline of control by the control device 50 in the first embodiment. As shown in the figure, first, the control device 50 causes the welding robot 10 to execute a control program acquired from the stacking planning device 30, and forms a first layer of a flow path with the welding torch 13 (S11).

[0024] Next, the control device 50 measures the cross-sectional shape of the first layer of the flow path using the shape measuring device 15 and obtains a shape profile, which is the measurement result of the cross-sectional shape (S12). Next, the control device 50 derives the gap width of the specified portion and the target position of the next layer from the shape profile obtained in S12 (S13). Next, the control device 50 compares the planned values ​​for the gap width and target position with the values ​​derived in S13, and corrects the stacking conditions and target position based on the comparison results (S14). Next, the control device 50 updates the control program based on the stacking conditions and target position corrected in S14 (S15).

[0025] Thereafter, the control device 50 repeats S11 to S15 for the second to n-th layers (S16). At this time, the control device 50 causes the welding robot 10 to execute the control program updated in S15 in S11. For convenience, the diagram shows S12 to S15 being executed for the n-th layer as well, but because the n-th layer of the flow passage is closed after being formed, strictly speaking, S12 to S15 do not need to be executed for the n-th layer.

[0026] Finally, the control device 50 causes the welding robot 10 to lay down a closing bead to close the gap, and the welding torch 13 lays down the closing bead (S17).

[0027] 4 is a diagram showing an example of the functional configuration of the stacking planning device 30 in the first embodiment. As shown in the figure, the stacking planning device 30 in the first embodiment includes a CAD data acquisition unit 41, a CAD data division unit 42, a stacking plan generation unit 43, and a stacking plan output unit 44.

[0028] The CAD data acquisition unit 41 acquires three-dimensional CAD data representing the three-dimensional shape of the layered object 100 from the CAD device 20. The CAD data division unit 42 generates a plurality of layer shape data representing the shape of each layer by dividing (slicing) the three-dimensional CAD data acquired by the CAD data acquisition unit 41 into a plurality of layers. In this case, the CAD data division unit 42 may convert the three-dimensional CAD data into an internal format that makes it easier to divide the data into a plurality of layers.

[0029] The lamination plan generation unit 43 generates a lamination plan including welding conditions and target positions for depositing beads that match the height and width of each layer based on the layer shape data generated by the CAD data division unit 42. To generate such a lamination plan, a model approximating the bead's cross-sectional shape is required, in addition to the bead height and width. These may be estimated by calculation based on actual measurements from measurement experiments or the cross-sectional area of ​​the deposited metal. In this embodiment, bead-on-plate welding and vertical lamination of several layers are performed while varying the deposition amount under several conditions of welding speed and wire feed speed, and the results of measuring the height and width per layer under each condition are stored in a database. Then, a welding speed and deposition amount that satisfy the desired height and width are selected during lamination, and the estimated shape of each layer is calculated as needed from the measurement results, and the target positions are determined. The calculation method for the weld cross-section may be changed depending on the material of the filler metal 14 and the shape of the already deposited portion. Lamination including the molded object is planned using this calculation method.

[0030] The stacking plan output unit 44 outputs the stacking plan generated by the stacking plan generating unit 43 to the recording medium 70 .

[0031] 5 is a diagram showing an example of the functional configuration of the control device 50 in the first embodiment. As shown in the figure, the control device 50 in the first embodiment includes a stacking plan acquisition unit 61, a control program storage unit 62, a control program execution unit 63, a planned value storage unit 64, a shape profile receiving unit 65, a gap width derivation unit 66, a stacking condition correction unit 68, and a control program update unit 69.

[0032] The lamination plan acquisition unit 61 acquires the lamination plan recorded on the recording medium 70. Here, the lamination plan may include a control program for controlling the welding robot 10. The lamination plan may also include planned values ​​such as the target position at which the welding robot 10 will lay the beads, the welding speed, the feed rate of the filler metal 14 (hereinafter simply referred to as the "feed rate"), the welding current, the welding voltage, the posture of the welding torch 13, and the order in which the beads will be laid. Furthermore, the lamination plan may also include at least one planned value of the shape information of the additively manufactured object 100, the height or width of the beads, and the cumulative value of the width or height of the beads during lamination. Furthermore, the lamination plan may also include a planned shape profile. As described below, the planned value of the gap width between the beads is determined by this planned shape profile. Then, the lamination plan acquisition unit 61 extracts the control program and the planned values ​​from the lamination plan. In this embodiment, a lamination plan acquisition unit 61 is provided as an example of an acquisition unit that acquires a planned value of the width of the gap formed by a plurality of weld beads from a lamination plan related to a process of forming a shaped object.

[0033] The control program storage unit 62 stores the control program extracted from the stacking plan by the stacking plan acquisition unit 61 .

[0034] The control program execution unit 63 executes the control program stored in the control program storage unit 62 or the control program updated by the control program update unit 69. As a result, the control program execution unit 63 controls the welding robot 10 to form a bead in accordance with the lamination plan generated by the lamination plan generation unit 43 or a lamination plan that has been subsequently modified.

[0035] Specifically, the control program execution unit 63 controls the welding robot 10 to form beads from the first layer to the nth layer. The control program execution unit 63 then controls the welding robot 10 to close the opened gap. When forming the bead of each layer, the functional units described below keep the gap width within a predetermined range, allowing the welding robot 10 to stably close the gap. The control program execution unit 63 may perform control when closing the gap differently from when forming the beads from the first layer to the nth layer. In particular, since the closing bead needs to achieve sufficient penetration to fully fuse with the beads on both ends of the gap, the control program execution unit 63 may perform control to adjust the heat input in accordance with the shape of the opening. Here, the control program execution unit 63 may perform control to adjust the heat input by adjusting the welding current, welding voltage, and / or the mixture ratio of the mixed shielding gas.

[0036] The plan value storage unit 64 stores the plan values ​​extracted from the stacking plan by the stacking plan acquisition unit 61 .

[0037] The shape profile receiving unit 65 receives, from the shape measuring device 15, a shape profile of the cross section of the layered additive object 100, which is formed by the control program executing unit 63 executing the control program. Here, when a plurality of independent beads form gaps in the layered additive object 100, the shape profile includes a plurality of shape profile portions corresponding to the plurality of independent beads. In this embodiment, the shape profile receiving unit 65 is provided as an example of a measuring unit that measures a plurality of shape profiles corresponding to a plurality of weld beads that are layered based on a lamination plan.

[0038] 6 shows an example of a shape profile received by the shape profile receiving unit 65. As shown in the figure, by updating the shape profile as the lamination progresses, it is possible to grasp the transition of the lamination shape from the shape profile. Also, as shown in the figure, by arranging target positions T1, T2, ..., Tn corresponding to the laminated beads B1, B2, ..., Bn in the shape profile so that they overlap, it is possible to compare the positional relationship between the bead shapes and the target positions.

[0039] The gap width derivation unit 66 derives the gap width and the target position of the next layer based on the shape profile received by the shape profile receiving unit 65 and the planned values ​​stored in the planned value storage unit 64 .

[0040] 6, the shape profile receiving unit 65 receives a shape profile such as that shown in Fig. 6. This shape profile includes curved bead walls on both the left and right sides. Therefore, the gap width deriving unit 66 derives the distance between the beads located at the tops of these bead walls as the gap width.

[0041] FIG. 7 illustrates a method for deriving the gap width in this case. In FIG. 7, the planned shape profile 610 is indicated by a dashed line, and the actual shape profile 620 is indicated by a solid line. The planned value of the gap width obtained from the planned shape profile 610 is designated GapP, and the actual values ​​of the gap width obtained from the actual shape profile 620 are designated GapG and GapR. A shape profile obtained using laser light (hereinafter referred to as a "sensor profile 630") may only provide information on a portion of the actual shape, as indicated by the thick solid line. In this case, GapG, which is the apparent closest distance between the beads, may differ from GapR, which is the actual closest distance between the beads. When a channel roof closure is planned, it is preferable to determine GapR. Therefore, the gap width derivation unit 66 may estimate GapR from GapG. Specifically, the gap width derivation unit 66 may convert GapG to GapR by obtaining an offset value corresponding to the relationship between GapG and GapR from a simple test specimen or the like. Alternatively, the gap width derivation unit 66 may estimate GapR by inputting GapG into a machine-learned model of the relationship between GapG and GapR obtained from the simple test specimen. The gap width derivation unit 66 may use a specific position on the sensor profile 630 when deriving GapG. However, it is preferable to use the tip position that protrudes most in the gap width direction on the sensor profile 630 as this specific position. In FIG. 7 , this tip position may be the boundary point between the range 621 where the sensor profile 630, indicated by the thick solid line, was acquired and the range 622 where the sensor profile 630, indicated by the thin solid line, was not acquired. Furthermore, new target positions TRR and TRL, which will be described later, may be considered as the tip position, or the tip position may be extracted taking into account the acquisition range of the sensor profile 630, etc.

[0042] In the present embodiment, this function of gap width derivation unit 66 is provided as an example of a derivation unit that derives an actual value of the gap width based on a plurality of shape profiles. Also, in the present embodiment, this function of gap width derivation unit 66 is provided as an example of a derivation unit that derives the distance between specific positions of each of the plurality of shape profiles as an actual value of the gap width. Furthermore, in the present embodiment, this function of gap width derivation unit 66 is provided as an example of a derivation unit that estimates the tip positions of each of the plurality of weld beads that protrude in the gap direction from the specific positions of each of the plurality of shape profiles, and derives the distance between the tip positions as an actual value of the gap width.

[0043] Furthermore, if the target position for the next layer is set at a position away from the surface of the bead, this may result in poor arc generation or poor lamination shape. Therefore, the gap width deriving unit 66 also derives the target position for the next layer.

[0044] 7 also shows a method for deriving the target positions in this case. The gap width deriving unit 66 derives new target positions TRR and TRL by extending the planned target positions TPR and TPL in the VR and VL directions, which are the lamination directions of the overhang angle θOH, and deriving the points at which the sensor profile 630 intersects with the sensor profile 630. Note that if the sensor profile 630 does not intersect with the VR and VL directions, it is advisable to derive the target positions of the next layer from a shape profile obtained by complementing with a predetermined bead shape model.

[0045] The lamination condition correcting unit 68 compares the actual gap width value and new target position derived by the gap width deriving unit 66 with the planned gap width and target position stored in the planned value storing unit 64 .

[0046] Specifically, the lamination condition correcting unit 68 compares the planned gap width value stored in the planned value storage unit 64 with the actual gap width value derived by the gap width deriving unit 66 to calculate the deviation ε. Here, the actual gap width value may be a value obtained directly from the sensor profile (e.g., GapG) or a value obtained by estimation based on the sensor profile (e.g., GapR). The lamination condition correcting unit 68 corrects the lamination conditions of the bead to be laminated on the next layer using a correction amount corresponding to the calculated deviation ε. For example, assuming that the target next layer is layer k, the deviation at that time is εk, and the change in deviation from the previous layer is Δεk, the lamination condition correcting unit 68 may correct the welding speed WeldVk using the correction amount shown in the following equation (1):

[0047]

[0048] Equation (1) is a PID control equation, where Kp represents the proportional gain, Kd represents the differential gain, Ki represents the integral gain, θOH represents the overhang angle, and φ represents the inclination angle of the welding torch 13 relative to the horizontal plane. In equation (1), the standard setting value of the welding speed is corrected based on the overhang angle θOH and the inclination angle φ of the welding torch 13, and the corrected welding speed is further corrected by a correction term dependent on the gap width deviation ε. Note that not all of the second to fourth terms on the right side of equation (1) need to be included. It is sufficient that at least one of the second to fourth terms is included. Furthermore, terms may be added or omitted as the build progresses. For example, the fourth term on the right side of equation (1) may be added from the mth layer, which is the intermediate layer. In this case, the value of m may be adjusted depending on the convergence of the deviation ε. Furthermore, the gains Kp, Kd, ​​and Ki may be adjusted depending on the conditions of the build bead, such as the overhang angle θOH. In equation (1), the gain Kp is corrected based on the overhang angle θOH. ​​This is because, as shown in Figure 7, even if the deposition amount of the bead is the same, the contribution to the gap width direction varies depending on the overhang angle θOH. ​​In this way, the layering condition correcting unit 68 corrects the welding speed using equation (1), but it may also correct the feed speed using an equation similar to equation (1).

[0049] In this embodiment, this function of the lamination condition correction unit 68 is provided as an example of a correction unit that corrects the lamination conditions of multiple weld beads so as to reduce the deviation between the planned gap width value and the actual gap width value. Furthermore, in this embodiment, Equation (1) is used as an example of a correction formula in which at least one of a proportional term, a differential term, and an integral term corresponding to the deviation is added to the standard set value of the lamination condition. In this embodiment, this function of the lamination condition correction unit 68 is provided as an example of a correction unit that corrects the lamination conditions using the correction formula. Furthermore, in this embodiment, this function of the lamination condition correction unit 68 is provided as an example of a correction unit that switches, as the lamination progresses, from a correction formula in which an integral term is not added to the standard set value of the lamination condition to a correction formula in which an integral term is added to the standard set value of the lamination condition.

[0050] Furthermore, the lamination condition correcting unit 68 compares the planned target positions stored in the planned value storage unit 64 with the new target positions derived by the gap width deriving unit 66 on the shape profile. At this time, the lamination condition correcting unit 68 also calculates the distances AR and AL between the planned target positions TPR and TPL and the new target positions TRR and TRL (see FIG. 7 ). Here, the new target positions TRR and TRL may be specific positions on the sensor profile 630. However, as described above, it is preferable that these specific positions be positions where the planned target positions TPR and TPL are extended in the VR and VL directions, which are the lamination directions of the overhang angle θOH, and intersect with the sensor profile 630 (see FIG. 7 ). The lamination condition correcting unit 68 then updates the target positions instructed to the welding robot 10 to the new target positions TRR and TRL using a correction vector, which is a correction amount using the distances AR and AL between the target positions, as shown in Equation (2) below.

[0051]

[0052] Here, Vj is a unit vector pointing from the target position of the current layer to the target position of the next layer. However, the angle that Vj forms with the horizontal plane is assumed to be an acute angle. If the target position is not updated in this way, the arc will not be generated correctly at the tip of the layered bead, which may cause the arc to become unstable or an error to occur in the welding power source, causing the welding device to stop.

[0053] In this embodiment, this function is provided in the stacking condition correction unit 68 as an example of a correction unit that corrects the planned value of the target position when stacking each of the multiple weld beads of the next layer to a specific position of each of the multiple shape profiles.

[0054] The control program update unit 69 updates the control program based on the correction amount calculated by the build condition correction unit 68. The beads to be updated are those at both ends of the gap. Since independently adjusting the deposition amount can easily result in uneven (asymmetric) shapes of the left and right beads, the correction amount for the welding speed or feed rate calculated from Equation (1) is applied to the build of the beads at both ends of the gap. Meanwhile, the correction amount for the target position may be adjusted separately for the left and right sides of the gap. For example, if the filler metal 14 is bent in a predetermined direction from the tip of the welding torch 13, the offset value applied according to the bending direction may be different for the bead to be built to the left of the gap and the bead to be built to the right of the gap. The control program update unit 69 may also correct the posture of the welding robot 10 in conjunction with the correction of the target position and deposition amount.

[0055] (Operation of Stacking Planning Device) Fig. 8 is a flowchart showing an example of the operation of the stacking planning device 30 in the first embodiment. As shown in the figure, in the stacking planning device 30, first, the CAD data acquisition unit 41 acquires three-dimensional CAD data from the CAD device 20 (step 301). Next, the CAD data division unit 42 divides the three-dimensional CAD data acquired in step 301 into a plurality of layers to generate layer shape data (step 302). Next, the stacking plan generation unit 43 generates a stacking plan from the layer shape data generated in step 302 (step 303). Next, the stacking plan output unit 44 outputs the stacking plan generated in step 303 to the recording medium 70 (step 304).

[0056] (Operation of Control Device) In the control device 50, first, the stacking plan acquisition unit 61 acquires a stacking plan from the recording medium 70, and stores the control program included in the stacking plan in the control program storage unit 62 and the plan values ​​included in the stacking plan in the plan value storage unit 64. Then, the control program execution unit 63 reads out the control program stored in the control program storage unit 62 and executes it, thereby starting the execution of the formation control process in the first embodiment.

[0057] 9 is a flowchart showing the details of the formation control process. As shown in the figure, first, the control program execution unit 63 sets the layer index i to 1 (step 501). Next, the control program execution unit 63 increments the layer index i by 1 up to the number of layers n, and performs the following process for each index i.

[0058] That is, the control program execution unit 63 controls the welding robot 10 to form the ith layer of the layered object 100 (step 502). Next, the control program execution unit 63 determines whether the layer index i has reached the number of layers n (step 503).

[0059] If it is determined that the layer index i has not reached the layer number n, the shape profile receiving unit 65 receives the shape profile from the shape measuring instrument 15 (step 504). Next, the gap width derivation unit 66 derives the actual gap width value and a new target position for the next layer based on the planned value stored in the planned value storage unit 64 and the shape profile received in step 504 (step 505). Next, the lamination condition correction unit 68 compares the planned gap width value stored in the planned value storage unit 64 with the actual gap width value derived in step 505 and corrects the lamination conditions so as to reduce the amount of deviation (step 506). Specifically, the lamination condition correction unit 68 calculates a correction amount corresponding to the amount of deviation and corrects the lamination conditions by this correction amount. Next, the lamination condition correction unit 68 compares the planned value of the target position for the next layer stored in the planned value storage unit 64 with the new target position for the next layer derived in step 505 and corrects the target position for the next layer (step 507). Specifically, the lamination condition correction unit 68 calculates a correction amount for the target position and corrects the target position by this correction amount. Next, the control program update unit 69 updates the control program being executed by the control program execution unit 63 based on the correction amounts calculated in steps 506 and 507 (step 508). Thereafter, the control program execution unit 63 adds 1 to the layer index i (step 509) and returns the process to step 502.

[0060] On the other hand, if it is determined that the layer index i has reached the number of layers n, the control program executing unit 63 controls the welding robot 10 to close the gap (step 510), and ends the process.

[0061] (Effects) In the first embodiment, when manufacturing an object in which a plurality of weld beads form gaps, the lamination conditions of the plurality of weld beads are corrected so as to reduce the deviation between the planned value and the actual value of the gap width, thereby making it possible to keep the gap width within an appropriate range.

[0062] Second Embodiment (Overview) The control by the control device 50 in the first embodiment may be combined with other control. For example, in the second embodiment, the gap width control in the first embodiment is combined with control based on the bead growth amount (hereinafter simply referred to as "growth amount"). For example, in a circular arch-shaped layered object 100, the first half layers (1, 2, 3, ..., m-1 layers) account for most of the height of the layered object 100. Therefore, it is preferable to control the growth amount in the first half layers from the perspective of managing the stack height. In the second half layers (m, m+1, ..., n layers), even if the number of layers increases, the increase in stack height is small. Therefore, the left-right bead spacing varies more significantly from layer to layer than the stack height. Therefore, by regarding the left-right bead spacing as the gap width and switching to gap width control, the spacing between the bead walls can be adjusted to an appropriate amount, making it easier to ensure the quality of the closed bead. Conversely, if the spacing between the bead walls is not appropriate, problems such as poor formation of the back bead or holes due to melt-through of the weld metal may occur.

[0063] 10 is a diagram showing an outline of another control by the control device 50 in the second embodiment. As shown in the figure, first, the control device 50 causes the welding robot 10 to execute a control program acquired from the stacking planning device 30, and forms a first layer of the flow path with the welding torch 13 (S21).

[0064] Next, the control device 50 measures the cross-sectional shape of the first layer of the flow channel using the shape measuring device 15 and obtains a shape profile, which is the measurement result of the cross-sectional shape (S22). Next, the control device 50 derives the growth amount and the target position of the next layer from the shape profile obtained in S22 (S23). Next, the control device 50 compares the planned values ​​for the growth amount and the target position with the values ​​derived in S23, and corrects the stacking conditions and the target position based on the comparison results (S24). Next, the control device 50 updates the control program based on the stacking conditions and the target position corrected in S24 (S25).

[0065] Thereafter, the control device 50 repeats S21 to S25 for the second to m-th layers (S26). At this time, the control device 50 causes the welding robot 10 to execute the control program updated in S25 in S21. For convenience, the figure shows S22 to S25 being executed for the m-th layer as well, but because control based on the gap width is performed after the m-th layer of the flow channel is formed, strictly speaking, instead of S22 to S25, S12 to S15 in FIG. 3 should be executed for the m-th layer.

[0066] (Functional Configuration of Stacking Planning Apparatus) An example of the functional configuration of the stacking planning apparatus 30 in the second embodiment is similar to the example of the functional configuration of the stacking planning apparatus 30 in the first embodiment, and therefore a description thereof will be omitted.

[0067] 11 is a diagram showing an example of the functional configuration of the control device 50 in the second embodiment. As shown in the figure, the control device 50 in the second embodiment includes a stacking plan acquisition unit 61, a control program storage unit 62, a control program execution unit 63, a planned value storage unit 64, a shape profile reception unit 65, a gap width derivation unit 66, a growth amount derivation unit 67, a stacking condition correction unit 68, and a control program update unit 69.

[0068] The stacking plan acquisition unit 61, control program storage unit 62, control program execution unit 63, planned value storage unit 64, shape profile receiving unit 65, and gap width derivation unit 66 are the same as those in the first embodiment, so their explanation will be omitted.

[0069] The growth amount derivation unit 67 derives the growth amount and the target position of the next layer based on the shape profile received by the shape profile receiving unit 65 and the planned values ​​stored in the planned value storage unit 64 .

[0070] The lamination condition correction unit 68 performs the following operation for the first to (m-1)th layers. That is, the lamination condition correction unit 68 compares the actual value of the growth amount and the new target position derived by the growth amount derivation unit 67 with the planned growth amount and target position stored in the planned value storage unit 64. Then, the lamination condition correction unit 68 updates the lamination conditions using an equation similar to Equation (1), with ε representing the deviation between the planned value of the growth amount stored in the planned value storage unit 64 and the actual value of the growth amount derived by the growth amount derivation unit 67. The lamination condition correction unit 68 also updates the target position of the next layer using an equation similar to Equation (2). In this embodiment, this function of the lamination condition correction unit 68 is provided as an example of a correction unit that executes a first correction method, which is a method of correcting the lamination conditions so as to reduce the deviation between the planned value of the growth amount in the lamination direction of each of the multiple weld beads and the actual value of the growth amount derived based on the shape profile.

[0071] For the mth to nth layers, the lamination condition correcting unit 68 performs the same operation as in the first embodiment. In this embodiment, this function of the lamination condition correcting unit 68 is provided as an example of a correcting unit that executes a second correction method for correcting the lamination conditions so as to reduce the deviation between the planned gap width value and the actual gap width value.

[0072] Furthermore, in this embodiment, a lamination condition correcting unit 68 is provided as an example of a correcting unit that switches the correction method for correcting lamination conditions from the first correction method to the second correction method as the lamination progresses.

[0073] The control program update unit 69 is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0074] (Operation of Stacking Planning Apparatus) An example of the operation of the stacking planning apparatus 30 in the second embodiment is similar to the example of the operation of the stacking planning apparatus 30 in the first embodiment, and therefore a description thereof will be omitted.

[0075] (Operation of Control Device) In the control device 50, first, the stacking plan acquisition unit 61 acquires the stacking plan from the recording medium 70, and stores the control program included in the stacking plan in the control program storage unit 62 and the plan values ​​included in the stacking plan in the plan value storage unit 64. Then, the control program execution unit 63 reads out the control program stored in the control program storage unit 62 and executes it, thereby starting the execution of the formation control process in the second embodiment.

[0076] 12 is a flowchart showing the details of the formation control process. As shown in the figure, first, the control program execution unit 63 sets the layer index i to 1 (step 551). Next, the control program execution unit 63 increments the layer index i by 1 up to the number of layers n, and performs the following process for each index i.

[0077] That is, the control program execution unit 63 controls the welding robot 10 to form the ith layer of the layered object 100 (step 552). Next, the control program execution unit 63 determines whether the layer index i has reached the number of layers n (step 553).

[0078] As a result, if it is determined that the layer index i has not reached the number of layers n, the shape profile receiving unit 65 receives a shape profile from the shape measuring instrument 15 (step 554). Next, the shape profile receiving unit 65 determines whether the layer index i has reached the number of layers m (step 555).

[0079] If it is determined that the layer index i has not reached the number of layers m, the growth amount derivation unit 67 derives the actual growth amount and a new target position for the next layer based on the planned value stored in the planned value storage unit 64 and the shape profile received in step 554 (step 556). Next, the lamination condition correction unit 68 compares the planned growth amount stored in the planned value storage unit 64 with the actual growth amount derived in step 556, and corrects the lamination conditions so as to reduce the amount of deviation (step 557). Specifically, the lamination condition correction unit 68 calculates a correction amount corresponding to the amount of deviation and corrects the lamination conditions by this correction amount.

[0080] On the other hand, if it is determined that the layer index i has reached the number of layers m, the gap width derivation unit 66 derives the actual gap width value and a new target position for the next layer based on the planned value stored in the planned value storage unit 64 and the shape profile received in step 554 (step 558). Next, the lamination condition correction unit 68 compares the planned gap width value stored in the planned value storage unit 64 with the actual gap width value derived in step 558, and corrects the lamination conditions so as to reduce the amount of deviation (step 559). Specifically, the lamination condition correction unit 68 calculates a correction amount corresponding to the amount of deviation and corrects the lamination conditions by this correction amount.

[0081] Next, the lamination condition correction unit 68 compares the planned value of the target position of the next layer stored in the planned value storage unit 64 with the new target position of the next layer derived in step 556 or step 558, and corrects the target position of the next layer (step 560). Specifically, the lamination condition correction unit 68 calculates a correction amount for the target position and corrects the target position by this correction amount. Next, the control program update unit 69 updates the control program being executed by the control program execution unit 63 based on the correction amount calculated in steps 557 and 560, or steps 559 and 560 (step 561). Thereafter, the control program execution unit 63 adds 1 to the layer index i (step 562), and the process returns to step 552.

[0082] On the other hand, if it is determined that the layer index i has reached the number of layers n, the control program execution unit 63 controls the welding robot 10 to close the gap (step 563), and ends the process.

[0083] (Effects) In the second embodiment, when manufacturing an object in which a plurality of weld beads form gaps, the layering conditions of the plurality of weld beads are corrected so that the deviation between the planned and actual values ​​of the growth amount is reduced in the first half, and the deviation between the planned and actual values ​​of the gap width is reduced in the second half. This makes it possible to keep the gap width within an appropriate range while satisfying the height and width of the object.

[0084] This application claims priority from Japanese Patent Application No. 2023-216840, filed December 22, 2023. Japanese Patent Application No. 2023-216840 is incorporated herein by reference.

[0085] The present disclosure may include the following aspects. (Aspect 1) A control method for an additive manufacturing device that builds a shaped object by stacking weld beads with a welding torch, the control method including: acquiring, from a stacking plan related to a process of building the shaped object, a planned value of a gap width formed by a plurality of weld beads; measuring a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; deriving an actual value of the gap width based on the plurality of shape profiles; and correcting stacking conditions for the plurality of weld beads so as to reduce a deviation between the planned value of the gap width and the actual value of the gap width. (Aspect 2) The control method for an additive manufacturing device according to Aspect 1, wherein, in the deriving, a distance between specific positions of each of the plurality of shape profiles is derives as the actual value of the gap width. (Aspect 3) The control method for an additive manufacturing device according to Aspect 2, wherein the specific position is a tip position of each of the plurality of shape profiles protruding in the direction of the gap. (Aspect 4) The method for controlling an additive manufacturing device according to any one of Aspects 1 to 3, wherein in the deriving step, a tip position of each of the plurality of weld beads protruding in the direction of the gap is estimated from a specific position of each of the plurality of shape profiles, and the distance between the tip positions is derived as an actual value of the gap width. (Aspect 5) The method for controlling an additive manufacturing device according to Aspect 4, wherein the specific position is a tip position of each of the plurality of shape profiles protruding in the direction of the gap. (Aspect 6) The method for controlling an additive manufacturing device according to any one of Aspects 1 to 5, wherein in the correcting step, the lamination conditions are corrected using a correction formula in which at least one of a proportional term, a differential term, and an integral term corresponding to the deviation amount is added to a standard setting value of the lamination condition. (Aspect 7) A control method for an additive manufacturing device according to Aspect 6, wherein in the correction step, the correction formula in which the integral term is not added to the standard setting value of the additive manufacturing condition is switched to the correction formula in which the integral term is added to the standard setting value of the additive manufacturing condition as the additive manufacturing process progresses.(Aspect 8) The control method for an additive manufacturing device according to any one of Aspects 1 to 7, wherein the correcting step corrects a planned value of a target position when stacking each of the plurality of weld beads of a next layer to a specific position of each of the plurality of shape profiles. (Aspect 9) The control method for an additive manufacturing device according to Aspect 8, wherein the specific position is a position where the planned value of the target position is extended in a stacking direction and intersects with each of the shape profiles. (Aspect 10) The control method for an additive manufacturing device according to Aspect 1, wherein the correcting step switches a correction method for correcting the stacking conditions from a first correction method to a second correction method according to progress of stacking, the first correction method being a method of correcting the stacking conditions so as to reduce a deviation between a planned value of a growth amount in the stacking direction of each of the plurality of weld beads and an actual value of the growth amount derived based on the shape profile, and the second correction method being a method of correcting the stacking conditions so as to reduce a deviation between a planned value of a width of the gap and an actual value of the width of the gap. (Aspect 11) A control device for an additive manufacturing device that builds a structure by stacking weld beads using a welding torch, the control device for the additive manufacturing device comprising: an acquisition unit that acquires planned values ​​for gap widths formed by a plurality of weld beads from a stacking plan for a process of building the structure; a measurement unit that measures a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; a derivation unit that derives an actual value for the gap width based on the plurality of shape profiles; and a correction unit that corrects stacking conditions for the plurality of weld beads so as to reduce a deviation between the planned value for the gap width and the actual value for the gap width.(Aspect 12) A program for causing a control device of an additive manufacturing device that uses a welding torch to stack weld beads to form a shaped object to implement the following functions: a function to obtain, from a stacking plan for a process of forming the shaped object, a planned value for the width of a gap formed by a plurality of weld beads; a function to measure a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; a function to derive an actual value for the width of the gap based on the plurality of shape profiles; and a function to correct the stacking conditions of the plurality of weld beads so as to reduce the amount of deviation between the planned value for the width of the gap and the actual value for the width of the gap.

[0086] 1...Metal additive manufacturing system, 10...Welding robot, 13...Welding torch, 15...Shape measuring instrument, 20...CAD device, 30...Lamination planning device, 41...CAD data acquisition unit, 42...CAD data division unit, 43...Lamination plan generation unit, 44...Lamination plan output unit, 50...Control device, 61...Lamination plan acquisition unit, 62...Control program storage unit, 63...Control program execution unit, 64...Planned value storage unit, 65...Shape profile receiving unit, 66...Gap width derivation unit, 67...Growth amount derivation unit, 68...Lamination condition correction unit, 69...Control program update unit, 70...Recording medium

Claims

1. A control method for an additive manufacturing device that forms a structure by stacking weld beads with a welding torch, the control method including the steps of: acquiring a planned value of the width of a gap formed by a plurality of weld beads from a stacking plan for a process of forming the structure; measuring a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; deriving an actual value of the width of the gap based on the plurality of shape profiles; and correcting stacking conditions for the plurality of weld beads so as to reduce a deviation between the planned value of the gap width and the actual value of the gap width.

2. A method for controlling an additive manufacturing device according to claim 1, wherein in the deriving step, a distance between specific positions of each of the plurality of shape profiles is derived as an actual value of the width of the gap.

3. The method for controlling an additive manufacturing device according to claim 2, wherein the specific position is a tip position of each of the plurality of shape profiles protruding in the direction of the gap.

4. A control method for an additive manufacturing device as described in claim 1, wherein in the deriving step, a tip position protruding in the direction of the gap of each of the plurality of weld beads is estimated from a specific position of each of the plurality of shape profiles, and the distance between the tip positions is derived as an actual value of the width of the gap.

5. A method for controlling an additive manufacturing device according to claim 4, wherein the specific position is a tip position of each of the plurality of shape profiles protruding in the direction of the gap.

6. A method for controlling an additive manufacturing device as described in claim 1, wherein in the correction step, the stacking conditions are corrected using a correction formula in which at least one of a proportional term, a differential term, and an integral term corresponding to the deviation amount is added to a standard setting value of the stacking conditions.

7. A control method for an additive manufacturing device as described in claim 6, wherein in the correction step, the correction formula in which the integral term is not added to the standard setting value of the additive manufacturing condition is switched to the correction formula in which the integral term is added to the standard setting value of the additive manufacturing condition as the additive manufacturing process progresses.

8. A control method for an additive manufacturing device as described in claim 1, wherein in the correction step, the planned value of the target position when stacking each of the multiple weld beads of the next layer is corrected to a specific position of each shape profile of the multiple shape profiles.

9. A method for controlling an additive manufacturing device as described in claim 8, wherein the specific position is a position where the planned value of the target position is extended in the stacking direction and intersects with each of the shape profiles.

10. A control method for an additive manufacturing device as described in claim 1, wherein in the correction step, a correction method for correcting the stacking conditions is switched from a first correction method to a second correction method according to progress of stacking, the first correction method is a method of correcting the stacking conditions so as to reduce an amount of deviation between a planned value of a growth amount in the stacking direction of each of the plurality of weld beads and an actual value of the growth amount derived based on the shape profile, and the second correction method is a method of correcting the stacking conditions so as to reduce an amount of deviation between a planned value of a width of the gap and an actual value of the width of the gap.

11. A control device for an additive manufacturing device that forms a structure by stacking weld beads with a welding torch, the control device comprising: an acquisition unit that acquires planned values ​​of gap widths formed by a plurality of weld beads from a stacking plan for a process of forming the structure; a measurement unit that measures a plurality of shape profiles respectively corresponding to the plurality of weld beads stacked based on the stacking plan; a derivation unit that derives actual values ​​of the gap widths based on the plurality of shape profiles; and a correction unit that corrects stacking conditions for the plurality of weld beads so as to reduce a deviation between the planned value of the gap width and the actual value of the gap width.

12. A program for implementing in a control device of an additive manufacturing device that forms a structure by stacking weld beads with a welding torch, the following functions: acquiring a planned value of the width of the gap formed by a plurality of weld beads from a stacking plan for a process of forming the structure; measuring a plurality of shape profiles corresponding to the plurality of weld beads stacked based on the stacking plan; deriving an actual value of the width of the gap based on the plurality of shape profiles; and correcting the stacking conditions of the plurality of weld beads so as to reduce the amount of deviation between the planned value of the gap width and the actual value of the gap width.

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