Additive manufacturing system

Abstract

This additive manufacturing system is provided with: a welding torch; a moving device that moves the welding torch; a wire feeding device; a welding power supply device; a control device; and a wire cutting device. The control device executes first processing (abnormality determination processing) for determining the presence or absence of abnormality in layering position height before starting layering of welding beads, and executes second processing (plan correction processing) for correcting a layering plan when it is determined by the first processing that there is abnormality. In the first processing, the control device measures a wire contact time, and determines that there is abnormality when a measurement result deviates from an appropriate time range. In the second processing, the control device uses the wire cutting device to set a wire protrusion length to a reference value and then measures the wire contact time, and corrects the layering plan on the basis of the measurement result.

Description

Additive Manufacturing System

[0001] The present disclosure relates to an additive manufacturing system that manufactures an object by stacking weld beads.

[0002] For example, Japanese Patent No. 7391709 (Patent Document 1) discloses an additive manufacturing system that corrects a stacking plan when manufacturing a shaped object by stacking weld beads. Specifically, this additive manufacturing system installs a camera in a position where it can capture an image of a cross section of a stacked body being manufactured, and determines a deviation in stacking position (the difference between the actual position and the planned position) based on the result of comparing a planned image of the stacked body with the captured image of the stacked body being manufactured, and corrects the position of a welding torch based on the result.

[0003] Patent No. 7391709

[0004] The additive manufacturing system disclosed in Japanese Patent No. 7391709 requires image processing to determine deviations in stacking positions, which raises concerns that the processing may become complicated.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to appropriately correct a stacking plan without performing image processing when forming a structure by stacking weld beads.

[0006] The additive manufacturing system according to the present disclosure is an additive manufacturing system that manufactures a shaped object by stacking weld beads, and includes: a welding torch that melts wire to form a weld bead; a movement device that moves the welding torch; a wire feeder that feeds wire to the welding torch; a power supply that supplies welding current to the wire; a control device that stacks the weld bead at a stacking position by controlling the movement device, the wire feeder, and the power supply according to a stacking plan; and a cutting device that cuts off the tip of the wire. The control device executes a first process to determine whether or not there is an abnormality in the height of the stacking position before starting to stack the weld beads, and if the first process determines that the height of the stacking position is abnormal, executes a second process to correct the stacking plan. In the first process, the control device starts wire feeding and measures a wire contact time from when wire feeding starts until the wire contacts the stacking position, and determines that the height of the stacking position is abnormal if the wire contact time deviates from an appropriate time range. In the second process, the control device sets the wire protrusion length, which is the length of the wire protruding from the welding torch, to a reference value by cutting the tip of the wire using a cutting device, starts feeding the wire after setting the wire protrusion length to the reference value, measures the wire contact time, calculates the difference between the actual value and the planned value of the height of the stacking position based on the wire contact time, and corrects the stacking plan based on the difference.

[0007] According to the present disclosure, when a shaped object is formed by stacking weld beads, the stacking plan can be appropriately corrected without performing image processing.

[0008] FIG. 1 is a diagram schematically showing an example of the configuration of an additive manufacturing system. FIG. 2 is a block diagram schematically showing the functions of a control device. FIG. 3 is a diagram for explaining a method for determining an abnormality in a stack height H by an abnormality determination process (first process). FIG. 4 is a diagram for explaining a method for calculating a difference ΔH by a plan correction process (second process). FIG. 5 is a flowchart showing an example of a processing procedure of a control device. FIG. 6 is a diagram showing the correspondence relationship between welding conditions and the deposition amount and heat input amount of a welded portion.

[0009] 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.

[0010] 1 is a diagram schematically illustrating an example of the configuration of an additive manufacturing system 1 according to this embodiment. The additive manufacturing system 1 is configured to manufacture an object 100 by stacking 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, a wire cutting device 62, and a control device 30.

[0011] 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 formed by melting consumable electrode wire 51 (hereinafter also simply referred to as "wire 51") are deposited. Robot arm 40 is controlled by control device 30 so that object 100 is formed by depositing weld beads 70.

[0012] A welding current is supplied to wire 51 from a power supply tip (not shown) located inside nozzle 21 of welding torch 20. Wire 51 is melted by arc 22 generated between wire 51 and base material 80 or an already deposited weld bead 70. Arc 22 melts wire 51 and base material 80 or an already deposited weld bead 70 simultaneously, forming a molten pool 23. The molten pool 23 grows as a result of a portion of wire 51 melted by arc 22 moving, and as the molten pool 23 cools and solidifies, a weld bead 70 is formed. Shielding gas is supplied to welding torch 20 by a shielding gas supply (not shown), and the shielding gas emerges from nozzle 21 and reaches arc 22 and molten pool 23.

[0013] Welding power supply 10 supplies a welding current to wire 51. The welding current may be DC or AC. When the welding current is AC, the magnitude of the welding current and the EN ratio may be set by control device 30. The EN ratio is the ratio of the time of the wire negative polarity period to the total time in one AC cycle. Alternatively, the EN ratio may be the ratio of the time integral of the negative polarity current in one AC cycle to the time integral of the current in one AC cycle (the sum of the time integral of the positive polarity current and the time integral of the negative polarity current).

[0014] Wire feeder 50 includes a roller and a motor (not shown). Wire feeder 50 drives the motor to rotate the roller, thereby feeding wire 51 to welding torch 20.

[0015] The wire cutting device 62 cuts the tip of the wire 51. While Fig. 1 illustrates a mobile configuration in which the wire cutting device 62 is attached to the nozzle 21 of the welding torch 20, the wire cutting device 62 may be a stationary type that is fixed to the floor surface on which the additive manufacturing system 1 is placed, for example. By cutting the tip of the wire 51 with the wire cutting device 62, the length of the wire 51 protruding from the power supply tip of the welding torch 20 (hereinafter also referred to as "wire protrusion length L") is reduced to a predetermined reference value L ０ It can be made into.

[0016] The control device 30 includes a CPU (Central Processing Unit), a memory, and input / output ports for inputting and outputting various signals (none of which are shown). These elements are connected via a bus.

[0017] Control device 30 controls robot arm 40, wire feeder 50, and welding power supply 10 in accordance with the stacking plan, thereby stacking weld beads 70 at the stacking positions. In this way, planned object 100 is formed by stacking weld beads 70. 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.

[0018] Control device 30 has a function of stacking weld beads 70 according to the stacking plan, as well as a function of evaluating whether weld beads 70 are stacked according to the stacking plan, and a function of correcting the stacking plan according to the evaluation result. Note that the control for realizing the functions of control device 30 may be processed by software or dedicated hardware (electronic circuitry).

[0019] 2 is a block diagram showing the functions of the control device 30. The control device 30 includes a plan storage unit 31 and a stacking command unit 32.

[0020] The plan storage unit 31 stores a stacking plan for the object 100, which is created based on three-dimensional data of the object 100 obtained by design. The stacking plan includes three-dimensional data of the planned path of stacking positions (the trajectory of the welding torch 20) and welding conditions at each position (welding speed, wire feed speed, welding current, welding voltage, EN ratio, etc.). The stacking plan stored in the plan storage unit 31 may be created inside the control device 30, or may be created outside the control device 30 and input to the control device 30.

[0021] Lamination command unit 32 controls robot arm 40, wire feeder 50, and welding power supply 10 so as to satisfy the trajectory and welding conditions included in the lamination plan stored in plan storage unit 31. In this way, object 100 planned in the lamination plan is formed by laminating weld beads 70.

[0022] The control device 30 according to this embodiment further includes a stack evaluation unit 33 and a plan correction unit 34 .

[0023] Before starting the next laying of weld bead 70 (or before starting laying of each path if the planned path is divided into multiple paths), layering evaluation unit 33 evaluates whether weld bead 70 is being laid according to the laying plan. Specifically, layering evaluation unit 33 executes an abnormality determination process (first process) that determines whether there is an abnormality in the height of the laying position where the next laying will start (hereinafter also referred to as "lamination height H"). In this embodiment, "height" refers to the distance in the laying direction from a reference (for example, base material 80).

[0024] When the stack height H is determined to be abnormal by the abnormality determination process (first process) of the stack evaluation unit 33, the plan correction unit 34 executes a plan correction process (second process) to correct the stacking plan stored in the plan memory unit 31.

[0025] FIG. 3 is a diagram illustrating a method for determining an abnormality in the stack height H by the abnormality determination process (first process) executed by the stack evaluation unit 33. Generally, the wire projection length L after welding varies and can vary within a range from a lower limit value Lmin to an upper limit value Lmax. Therefore, even if the stack height H is normal (as planned), the distance between the wire tip and the stack position after welding (hereinafter also referred to as the "gap distance D") can also vary. Taking this into consideration, when the average value of the gap distance D when the stack height H is normal is defined as the "appropriate distance d," the stack height H is considered to be normal when the gap distance D after welding is within a range of the appropriate distance d and a predetermined value a, i.e., within the range from the lower limit distance (d-a) to the upper limit distance (d+a).

[0026] In the abnormality determination process, the stack evaluation unit 33 starts feeding the wire 51 while applying a weak voltage to the wire 51 that is not strong enough to melt the wire 51, and measures the time from when the feed of the wire 51 starts until the tip of the wire 51 abuts on the stack position and current starts to flow as the "wire abutment time T." ｍｉｎ From the upper limit time t ｍａｘ The range from the lower limit time t to the lower limit time t is set as the appropriate time range, and it is determined whether the wire contact time T is within the appropriate time range. ｍｉｎis the value obtained by dividing the lower limit distance (da) by the wire feed speed V, and the upper limit time t ｍａｘ is the value obtained by dividing the upper limit distance (d+a) by the wire feed speed V.

[0027] If the wire contact time T is within the appropriate time range, the stacking evaluation unit 33 determines that the stacking height H is normal (i.e., as planned). If the stacking height H is determined to be normal, the stacking evaluation unit 33 instructs the stacking command unit 32 to start the next stacking without correcting the stacking plan.

[0028] On the other hand, if the wire contact time T deviates from the appropriate time range, the stack evaluation unit 33 determines that the stack height H is abnormal (i.e., deviates from the plan) and notifies the plan correction unit 34 that the stack height H is abnormal.

[0029] When the plan correction unit 34 receives notification that the stack height H is abnormal, it calculates the difference ΔH between the actual value and the planned value of the stack height H, and executes a plan correction process (second process) to correct the stacking plan based on the difference ΔH.

[0030] 4 is a diagram for explaining a method for calculating the difference ΔH by the plan correction process (second process) executed by the plan correction unit 34. In order to correct the stacking plan, it is important to accurately grasp the difference ΔH between the actual value and the planned value of the stack height H.

[0031] The actual value of stack height H can be calculated using the following formula (1): In formula (1), the "nozzle height" is the height of the tip of nozzle 21 of welding torch 20 (the part from which wire 51 protrudes).

[0032] Stacking height H = (nozzle height) - (wire protrusion length L) - (gap distance D) (1) The nozzle height can be accurately determined by measuring the posture of the robot arm 40, and the gap distance D can be accurately determined by measuring the wire contact time T. However, as described above, the wire protrusion length L varies.

[0033] Therefore, in the plan correction process, the plan correction unit 34 first cuts the tip of the wire 51 with the wire cutting device 62 to reduce the wire protrusion length L to the reference value L. ０ This eliminates the influence of variations in the wire projection length L after welding.

[0034] The plan correction unit 34 calculates the wire protrusion length L as a reference value L ０ After this, feeding of the wire 51 is started and the wire contact time T is measured. The method for measuring the wire contact time T is the same as the method described in the abnormality determination process.

[0035] Next, the plan correction unit 34 calculates the gap distance D by multiplying the measured wire contact time T by the wire feed speed V, and calculates the difference ΔH using the following equation (2).

[0036] Difference ΔH = reference distance d ０ -gap distance D (2) In the formula (2), "reference distance d ０ " is the wire protrusion length L is the reference value L ０ When the difference ΔH is a positive value, the gap distance D is equal to or greater than the reference distance d ０ In other words, when the difference ΔH is a negative value, the gap distance D is smaller than the reference distance d ０ That is, the actual value of the stack height H is lower than the planned value.

[0037] Then, the plan correcting unit 34 corrects the stacking plan based on the difference ΔH. Specifically, the plan correcting unit 34 corrects the stacking plan so as to correct the difference ΔH in the next stacking. The method of correcting the stacking plan will be described in detail later.

[0038] 5 is a flowchart showing an example of a processing procedure when control device 30 executes the laying of weld bead 70. This flowchart is repeatedly executed each time laying of weld bead 70 starts (when the planned path is divided into multiple paths, each time laying of each path starts).

[0039] Before starting to lay weld bead 70 (step S30), control device 30 first executes the abnormality determination process (first process) described above in steps S10 to S13.

[0040] Specifically, the control device 30 starts feeding the wire 51 and measures the wire contact time T (step S10). ｍｉｎ From the upper limit time t ｍａｘ It is determined whether the time is within the appropriate time range (step S11).

[0041] If wire contact time T is within the appropriate time range (YES in step S11), control device 30 determines that build height H is normal (step S13). Thereafter, control device 30 starts building weld bead 70 in accordance with the current build plan (step S30) without executing the plan correction process (processing of steps S20 to S23).

[0042] On the other hand, if the wire contact time T deviates from the appropriate time range (NO in step S11), the control device 30 determines that the stack height H is abnormal (step S12) and executes the plan correction process (processing of steps S20 to S23).

[0043] In the plan correction process, the control device 30 first operates the wire cutting device 62 to set the wire protrusion length L to the reference value L. ０ (Step S20), and then start feeding of wire 51 to measure wire contact time T (Step S21). Then, control device 30 calculates the gap distance D by multiplying the measured wire contact time T by the wire feed speed V, and calculates the difference ΔH between the actual value and the planned value of stack height H using the above-mentioned equation (2) (Step S22). Then, control device 30 corrects the stacking plan based on the difference ΔH (Step S30).

[0044] The lamination plan correction method executed in step S30 will be described below. FIG. 6 is a diagram showing the correspondence between the welding conditions (welding current value, welding speed, EN ratio) and the deposition amount and heat input of the welded portion. As shown in FIG. 6, the deposition amount and heat input can be increased by increasing the welding current value. Furthermore, the deposition amount and heat input can be decreased by increasing the welding speed. Furthermore, when the welding current is AC, the deposition amount can be increased while maintaining the heat input by increasing the EN ratio.

[0045] The control device 30 corrects the stacking plan based on the correspondence relationship shown in Figure 6. For example, when the actual value of the stack height H is lower than the planned value, the control device 30 can increase the deposition amount at the next stacking position by performing at least one of a process of increasing the magnitude of the welding current and a process of decreasing the welding speed. Furthermore, when the welding current is AC, the control device 30 can increase the deposition amount at the next stacking position while maintaining the heat input at the next stacking position by increasing the EN ratio. These plan corrections can reduce the difference ΔH in the next stacking.

[0046] The method for correcting the stacking plan by the plan correction process is not limited to the above. For example, it may be determined whether the difference ΔH is greater than a threshold value, and if the difference ΔH is greater than the threshold value, a planned path for the stacking positions may be regenerated. Also, interrupting the stacking plan is one example of a method for correcting the stacking plan.

[0047] As described above, control device 30 according to this embodiment executes an abnormality determination process (first process) to determine whether or not there is an abnormality in stacking height H before starting to stack weld bead 70, and executes a plan correction process (second process) to correct the stacking plan if the abnormality determination process determines that stacking height H is abnormal. In both the abnormality determination process (first process) and the plan correction process (second process), stacking height H is determined by the simple process of measuring wire contact time T, so no complex image processing is required. Furthermore, in the plan correction process (second process), the tip of wire 51 is cut by wire cutting device 62 to set wire protrusion length L to reference value L.０ In this state, the wire contact time T is measured, and the difference ΔH between the actual value and the planned value of the stack height H is determined based on the measurement result. Therefore, the difference ΔH can be accurately calculated while eliminating the influence of variations in the wire projection length L after welding, and the stacking plan can be corrected based on the accurately calculated difference ΔH. As a result, the stacking plan can be appropriately corrected without performing image processing.

[0048] Furthermore, when the stack height H is determined to be normal in the abnormality determination process, the control device 30 according to this embodiment starts the next stacking without executing the plan correction process. Therefore, the next stacking can be started more quickly than when the plan correction process is always executed.

[0049] [Aspects] 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.

[0050] (Item 1) An additive manufacturing system according to the present disclosure is an additive manufacturing system that manufactures a shaped object by stacking weld beads, and includes: a welding torch that melts wire to form a weld bead; a movement device that moves the welding torch; a wire feeder that feeds wire to the welding torch; a power supply that supplies welding current to the wire; a control device that stacks the weld bead at a stacking position by controlling the movement device, the wire feeder, and the power supply according to a stacking plan; and a cutting device that cuts off the tip of the wire. Before starting to stack the weld beads, the control device executes a first process to determine whether or not there is an abnormality in the height of the stacking position, and if the first process determines that the height of the stacking position is abnormal, executes a second process to correct the stacking plan. In the first process, the control device starts wire feeding and measures a wire contact time from when wire feeding starts until the wire contacts the stacking position, and determines that the height of the stacking position is abnormal if the wire contact time deviates from an appropriate time range. In the second process, the control device sets the wire protrusion length, which is the length of the wire protruding from the welding torch, to a reference value by cutting the tip of the wire using a cutting device, starts feeding the wire after setting the wire protrusion length to the reference value, measures the wire contact time, calculates the difference between the actual value and the planned value of the height of the stacking position based on the wire contact time, and corrects the stacking plan based on the difference.

[0051] According to the additive manufacturing system of paragraph 1, if the height of the stacking position is determined to be abnormal by the first process, the stacking plan is corrected by the second process. In both the first process and the second process, the height of the stacking position is determined by the simple process of measuring the wire contact time, so complex image processing is not required. Furthermore, in the second process, the wire contact time is measured with the tip of the wire cut and the wire extension length set to a reference value, and the height of the stacking position is determined based on the measurement results. Therefore, the influence of variations in the wire extension length after welding can be eliminated, and the difference between the actual height of the stacking position and the planned value can be accurately calculated, and the stacking plan is corrected based on the accurately calculated difference. As a result, the stacking plan can be appropriately corrected without performing image processing.

[0052] (Item 2) In the additive manufacturing system described in Item 1, the stacking plan includes welding conditions for the stacking positions. In the second process, the control device corrects the welding conditions for the stacking positions so as to correct the difference by stacking the next weld bead.

[0053] According to the additive manufacturing system of the second paragraph, the welding conditions for the next stacking position are corrected to correct the difference between the actual height value and the planned height value of the stacking position. Therefore, by performing the next stacking, the difference between the actual height value and the planned height value of the stacking position can be reduced.

[0054] (Item 3) In the additive manufacturing system described in Item 2, the welding conditions for the stacking position include a magnitude of the welding current and a welding speed, which is the movement speed of the welding torch. If the actual value of the height of the stacking position is lower than the planned value in the second process, the control device performs at least one of a process of increasing the magnitude of the welding current and a process of decreasing the welding speed.

[0055] According to the additive manufacturing system of the third aspect, when the actual height of the stacking position is lower than the planned value, the deposition amount at the next stacking position is increased by increasing the welding current or decreasing the welding speed included in the stacking plan, thereby making it possible to reduce the difference between the actual height of the stacking position and the planned value by the next stacking.

[0056] (4) In the additive manufacturing system described in 2, the welding current is an AC current. The welding conditions for the stacking position include an EN ratio of the welding current. The EN ratio is the ratio of the time of the wire negative polarity period to the total time in one AC cycle, or the ratio of the time integration value of the negative polarity current in one AC cycle to the time integration value of the current in one AC cycle. In the second process, if the height of the stacking position is lower than the height of the stacking position, the control device performs a process to increase the EN ratio.

[0057] According to the additive manufacturing system of the fourth aspect, when the actual height of the stacking position is lower than the planned value, the deposition amount at the next stacking position is increased by increasing the EN ratio included in the stacking plan, thereby reducing the difference between the actual height of the stacking position and the planned value.

[0058] (Item 5) In the additive manufacturing system according to item 1, the stacking plan includes a trajectory of the stacking position. In the second process, if the magnitude of the difference is greater than a threshold value, the control device regenerates the trajectory of the stacking position.

[0059] According to the additive manufacturing system of the fifth aspect, if the magnitude of the difference is large, the trajectory of the stacking position can be regenerated.

[0060] (Item 6) In the additive manufacturing system described in any one of Items 1 to 5, if the control device determines that the height of the stacking position is normal by the first process, it starts stacking the weld beads without performing the second process.

[0061] According to the additive manufacturing system of paragraph 6, if the height of the stacking position is determined to be normal in the first process, the next stacking is started without performing the processes in the second process (cutting the wire tip, measuring the wire contact time, calculating the stacking height error, and correcting the stacking plan). Therefore, the next stacking can be started quickly.

[0062] 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.

[0063] 1 Additive manufacturing system, 10 Welding power supply, 20 Welding torch, 21 Nozzle, 22 Arc, 23 Weld pool, 30 Control device, 31 Plan memory unit, 32 Lamination command unit, 33 Lamination evaluation unit, 34 Plan correction unit, 40 Robot arm, 50 Wire feeder, 51 Consumable electrode wire, 62 Wire cutting device, 70 Weld bead, 80 Base material, 100 Model.

Claims

1. An additive manufacturing system that forms a shaped object by stacking weld beads, comprising: a welding torch that melts wire to form the weld bead; a movement device that moves the welding torch; a feed device that feeds the wire to the welding torch; a power supply device that supplies welding current to the wire; a control device that stacks the weld bead at a stacking position by controlling the movement device, the feed device, and the power supply device in accordance with a stacking plan; and a cutting device that cuts off the tip of the wire; wherein the control device executes a first process to determine whether or not there is an abnormality in the height of the stacking position before starting to stack the weld beads, and executes a second process to correct the stacking plan if the first process determines that the height of the stacking position is abnormal; in the first process, the control device starts feeding of the wire and measures a wire contact time from when the wire starts feeding to when the wire contacts the stacking position; and determines that the height of the stacking position is abnormal if the wire contact time deviates from an appropriate time range; and in the second process, the control device executes an additive manufacturing system that uses the cutting device to cut the tip of the wire, thereby setting a wire protrusion length, which is the length of the wire protruding from the welding torch, to a reference value; after setting the wire protrusion length to the reference value, starts feeding the wire and measures the wire contact time; calculates the difference between the actual value and the planned value of the height of the stacking position based on the wire contact time; and corrects the stacking plan based on the difference.

2. The additive manufacturing system of claim 1, wherein the stacking plan includes welding conditions for the stacking position, and the control device corrects the welding conditions for the stacking position in the second process so as to correct the difference by the next stacking of the weld bead.

3. The additive manufacturing system of claim 2, wherein the welding conditions for the stacking position include the magnitude of the welding current and a welding speed, which is the movement speed of the welding torch, and wherein the control device, in the second process, performs at least one of a process of increasing the magnitude of the welding current and a process of decreasing the welding speed when the actual value of the height of the stacking position is lower than the planned value.

4. The additive manufacturing system of claim 2, wherein the welding current is an AC current, the welding conditions for the stacking position include an EN ratio of the welding current, and the EN ratio is the ratio of the time of a wire negative polarity period to the total time in one AC cycle, or 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, and the control device performs processing to increase the EN ratio if the height of the stacking position is lower than the height of the stacking position in the second processing.

5. The additive manufacturing system of claim 1, wherein the stacking plan includes a trajectory of the stacking position, and the control device regenerates the planned path of the stacking position if the magnitude of the difference is greater than a threshold value in the second process.

6. An additive manufacturing system according to any one of claims 1 to 5, wherein the control device starts stacking the weld beads without executing the second process if the height of the stacking position is determined to be normal by the first process.

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