Lamination molding system

Abstract

A lamination molding system (1) includes: a welding torch (20), a robot arm (40), a welding power source (10), and a control device (30) for controlling the frequency of an alternating current and an EN ratio. Regardless of the frequency of the alternating current, the change period of the EN ratio is constant. The control device (30) sets the frequency of the alternating current to a value of 2 to 30 Hz.

Description

Additive Manufacturing System

[0001] The present disclosure relates to additive manufacturing systems.

[0002] Japanese Patent Laid-Open Publication No. 2022-106172 (Patent Document 1) discloses a method for forming a shaped object by stacking weld beads, and changing the welding conditions if the height of the weld bead deviates from the planned height. In Japanese Patent Laid-Open Publication No. 2022-106172 (Patent Document 1), a consumable electrode is used when stacking the weld beads, and the welding speed is changed depending on the stack height.

[0003] Japanese Patent Application Laid-Open No. 2022-106172

[0004] When stacking weld beads, if not only the deposition amount but also the heat input, which is the amount of heat applied to the molten part from outside, is taken into consideration, the shape of the stacked weld bead may not be stable. In JP 2022-106172 (Patent Document 1), when a consumable electrode is used, changing the deposition amount to change the height of the weld bead also changes the magnitude of the welding current, which affects the heat input, so there is a possibility that the heat input to the weld bead may be excessive or insufficient, and it was not sufficient to stack weld beads in a stable shape.

[0005] An object of the present disclosure is to provide a technique capable of stably building up weld beads in consumable electrode arc welding involving short-circuit transfer.

[0006] The present disclosure relates to an additive manufacturing system that uses a consumable electrode arc welding method with short-circuit transfer to supply a welding current to a consumable electrode wire and build up a weld bead to manufacture a shaped object. The additive manufacturing system includes a welding torch that builds up the weld bead using the consumable electrode wire, a drive device that moves the welding torch, a welding power source that supplies AC current to the consumable electrode wire as the welding current, and a control device that controls the AC frequency and EN ratio. The control device sets the AC frequency to a value between 2 Hz and 30 Hz.

[0007] The amount of weld bead deposition can be easily changed by changing the EN ratio, even with the same welding current. The additive manufacturing system of the present disclosure sets the AC frequency to a value between 2 Hz and 30 Hz. This allows the additive manufacturing system of the present disclosure to finely adjust the EN ratio while ensuring stability in the layering direction, thereby enabling stable layering of the weld bead when using a consumable electrode wire.

[0008] FIG. 1 is a diagram schematically illustrating an additive manufacturing system according to a first embodiment. FIG. 2 is a diagram for explaining an EN ratio. FIG. 3 is a diagram for explaining differences in EN ratios in one AC cycle. FIG. 4 is a diagram for explaining the stacked state of weld beads when the frequency is low. FIG. 5 is a diagram for explaining an example of welding conditions according to the first embodiment. FIG. 6 is a diagram showing the cross-sectional shape of stacked weld beads. FIG. 7 is a diagram for explaining an appropriate range of frequency according to the first embodiment. FIG. 8 is a flowchart showing control content according to the first embodiment. FIG. 9 is a diagram schematically illustrating an additive manufacturing system according to a second embodiment.

[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 additive manufacturing system 1 according to embodiment 1. The additive manufacturing system 1 includes a robot arm 40, a welding torch 20, a welding power source 10, a wire feeder 50, and a control device 30.

[0011] The robot arm 40 is a multi-joint arm, for example a six-axis multi-joint arm. The robot arm 40 functions as a drive device that moves the welding torch 20 at a set welding speed. As the robot arm 40 moves the welding torch 20, a weld bead 70 formed by melting the consumable electrode wire 51 is deposited. The robot arm 40 operates to form a shaped object by depositing the weld beads 70. The layer deposited immediately before the layer on which the current weld bead 70 is deposited is referred to as the previous layer.

[0012] In the welding torch 20, a welding current is supplied to a consumable electrode wire 51 at a power supply tip (not shown) located inside the nozzle 21. The consumable electrode wire 51 melts due to the arc 22 generated between the base material 80 or the already deposited weld bead 70 and resistance heat generated by the current flow. The melting of the consumable electrode wire 51 forms the weld bead 70. The welding torch 20 deposits the weld bead 70 using the consumable electrode wire 51. A shielding gas supply (not shown) supplies a shielding gas to the welding torch 20, which exits the nozzle 21 and reaches the arc 22 and the weld zone. The shielding gas may be, for example, argon, CO ２ and the like, and mixed gases containing these are used.

[0013] Torch cable 11 connected to welding torch 20 contains a cable for current supplied from welding power source 10, a consumable electrode wire 51 fed from wire feeder 50, and piping for shielding gas supplied from a shielding gas supply unit (not shown).

[0014] Welding power source 10 supplies AC as a welding current to consumable electrode wire 51. The magnitude of the welding current output from welding power source 10 and the EN ratio are set by control device 30. Here, the EN ratio is the ratio of the time during which the wire is negative polarity to the total time in one AC cycle. Alternatively, the EN ratio may be the ratio of the time-integrated value of the negative polarity current in one AC cycle to the time-integrated value of the current in one AC cycle (the sum of the time-integrated value of the positive polarity current and the time-integrated value of the negative polarity current).

[0015] FIG. 2 is a diagram illustrating the EN ratio. FIG. 2 shows a waveform for short-circuit welding with short-circuit transition. The welding power source 10 switches between electrode positive polarity (also referred to as EP polarity) and electrode negative polarity (also referred to as EN polarity) supplied to the consumable electrode wire 51 of the welding torch 20. Electrode positive polarity (EP polarity) refers to a polarity state in which the consumable electrode wire 51 side of the current path supplied from the welding power source 10 is the anode and the base material 80 or weld bead 70 side is the cathode. Electrode negative polarity (EN polarity) refers to a polarity state in which the base material 80 or weld bead 70 side of the current path supplied from the welding power source 10 is the anode and the consumable electrode wire 51 side is the cathode.

[0016] One AC cycle is defined as the time from when the electrode switches from negative to positive polarity to when the electrode switches from positive to negative polarity and back to positive again. The proportion of positive electrode polarity in one cycle is called the EP ratio, and the proportion of negative electrode polarity in one cycle is called the EN ratio. As shown in Figure 2, welding power source 10 can output a welding current in which the electrode polarity alternates between positive and negative electrode polarity in one cycle.

[0017] It is known that the wire melting rate of the consumable electrode wire 51 increases during periods of electrode negative polarity. This is because the amount of heat input from the arc 22 to the consumable electrode wire 51 is greater during periods of electrode negative polarity than during periods of electrode positive polarity. Conversely, during periods of electrode positive polarity, the amount of heat input from the arc 22 to the base material 80 or weld bead 70 is greater than during periods of electrode negative polarity, resulting in increased heat input to the molten zone. In this way, the heat input to the molten zone can be adjusted by changing the EN ratio.

[0018] Here, in an object formed by stacking weld beads 70, the lower the layer, the closer it is to the base material 80, and the easier it is for heat to escape, while the higher the layer, the further it is to the base material 80, and the harder it is for heat to escape. In such a case, if stacking is continued with the same welding current, the temperature of the weld beads 70 in the upper layers may become too high, and the weld beads 70 may melt away. The additive manufacturing system 1 according to the first embodiment adjusts the amount of heat input to the molten part by setting an appropriate EN ratio.

[0019] 1 , wire feeder 50 includes a roller and a motor (not shown). Wire feeder 50 feeds consumable electrode wire 51 to welding torch 20 by driving the motor to rotate the roller. The operation of wire feeder 50 is controlled by welding power source 10 based on commands from control device 30. The operation of wire feeder 50 may also be directly controlled by welding power source 10.

[0020] The control device 30 includes an arithmetic unit 31, a memory 32, a storage device 33, and an input / output interface 34. These components are connected via a bus.

[0021] The arithmetic device 31 is a computing entity (computer) that executes predetermined processing. The arithmetic device 31 is configured with a processor such as a central processing unit (CPU), a micro-processing unit (MPU), a tensor processing unit (TPU), or a graphics processing unit (GPU). The arithmetic device 31 can also be interpreted as a processing circuitry that executes predetermined processing.

[0022] The memory 32 includes a storage area (for example, a working area) for storing program code or work memory when the arithmetic unit 31 executes various programs.

[0023] The storage device 33 functions as a storage unit that stores various programs and various data executed by the arithmetic device 31. For example, the storage device 33 stores a control program 330 executed by the arithmetic device 31.

[0024] The input / output interface 34 receives input of various data and outputs data obtained by various processes in accordance with instructions from the arithmetic unit 31.

[0025] Here, the control device 30 controls, for example, the operation of the robot arm 40. The control device 30 calculates the EN ratio, frequency, etc. of the AC and displays them on a display device (not shown). The calculation and display of the EN ratio, frequency, etc. of the AC may be performed by the welding power source 10. In this way, a condition setting device that sets the AC conditions may be incorporated into either the control device 30 or the welding power source 10.

[0026] Next, differences in the EN ratio in one AC cycle with different frequencies will be described. Fig. 3 is a diagram for explaining differences in the EN ratio in one AC cycle. Fig. 3(A) is a diagram for explaining the EN ratio in one AC cycle when the AC frequency is low. Fig. 3(B) is a diagram for explaining the EN ratio in one AC cycle when the AC frequency is high. Fig. 3(C) is a diagram for explaining a state in which the EN ratio in one AC cycle of Fig. 3(B) is changed.

[0027] A low AC frequency is, for example, a frequency lower than 2 Hz. A high AC frequency is, for example, a frequency higher than 30 Hz. When the AC frequency is low, the duration of one AC cycle is long, as shown in Figure 3(A). Conversely, when the AC frequency is high, the duration of one AC cycle is short, as shown in Figures 3(B) and (C).

[0028] Here, arc welding with short-circuit transfer is a type of welding that alternates between an arc period in which an arc discharge occurs between electrodes and a short-circuit period in which the electrodes come into contact and form an electrical short circuit. One cycle of this short-circuit period and arc period is called a short-circuit-arc period. The short-circuit-arc period is the minimum period required to change the EN ratio (change the polarity state). The short-circuit-arc period is the same period as the transfer period in which droplet transfer occurs, in which the consumable electrode wire 51 melts and transfers to the base material 80 or an already deposited weld bead 70.

[0029] As shown in Figure 3, short-circuit-arc cycles of EP polarity are repeated during the EP period, and short-circuit-arc cycles of EN polarity are repeated during the EN period. To change the EN ratio, the time ratio of EN polarity in one AC cycle is changed. In other words, if the EN ratio is increased, the number of short-circuit-arc cycles in the EP period decreases, and the number of short-circuit-arc cycles in the EN period increases.

[0030] When the AC frequency is low as shown in Figure 3(A), the total number of short-circuit-arc periods in one AC cycle is large, so there are more ways to allocate the EP period and the EN period, and the degree of freedom in changing the EN ratio is higher than when the AC frequency is high as shown in Figures 3(B) and (C). In other words, the number of times the EN ratio can be changed when the frequency is low in one AC cycle can be set to be greater than the number of times the EN ratio can be changed when the frequency is high in one AC cycle.

[0031] Specifically, if one wishes to increase the number of times the EN ratio can be changed and adjust the EN ratio more finely (if one wishes to reduce the adjustment unit of the EN ratio), one can simply lower the AC frequency so that the period of one AC cycle becomes longer, as shown in Figure 3(A). Conversely, if one wishes to decrease the number of times the EN ratio can be changed and increase the adjustment unit of the EN ratio, one can simply raise the AC frequency so that the period of one AC cycle becomes shorter, as shown in Figures 3(B) and 3(C).

[0032] However, if the AC frequency is increased too much, the duration of one AC cycle becomes too short, making it almost impossible to adjust the EN period, as shown in Figures 3(B) and 3(C). For example, in Figures 3(B) and 3(C), the EN period can only be adjusted over a period equivalent to three change cycles. This results in an extremely limited number of changes to the EN ratio.

[0033] 4 is a diagram illustrating the layering state of the weld bead 70 when the frequency is low. As shown in FIG. 4, if the frequency of the AC is lowered too much (for example, to 1 Hz), the duration of one AC cycle becomes longer, and the EP period and / or the EN period that can be set becomes too long.

[0034] As a result, as shown in Figure 4, the temperature of the molten part is not uniform, and the shape of the weld bead 70 in the layering direction, which is approximately perpendicular to the welding direction indicated by the arrow, is unstable. For these reasons, it is desirable to change the EN ratio within an appropriate range of AC frequency. The additive manufacturing system 1 uses the control device 30, which controls the AC frequency and EN ratio, to set the AC frequency to a value within a range appropriate for layering, and changes the EN ratio within the set range.

[0035] The range of AC frequencies suitable for lamination was examined under the following welding conditions. FIG. 5 is a diagram illustrating an example of welding conditions according to the first embodiment. As shown in FIG. 5 , in the EP polarity period, the welding conditions are as follows: the feed rate of the consumable electrode wire 51 is 450 cm / min, the welding speed at which the welding torch 20 is driven is 50 cm / min, the current is 110 A, and the voltage is 16.4 V. As shown in FIG. 5 , in the EN polarity period, the welding conditions are as follows: the feed rate of the consumable electrode wire 51 is 450 cm / min, the welding speed at which the welding torch 20 is driven is 50 cm / min, the current is 75 A, and the voltage is 14.4 V. The welding conditions in FIG. 5 are merely an example; AC conditions in which the current is fixed and the feed rate of the consumable electrode wire 51 is variable during the EP and EN periods may also be used.

[0036] The cross-sectional shape of the weld bead 70, which is layered in multiple layers when a welding current is supplied to the consumable electrode wire 51 under the above welding conditions, will now be described. Fig. 6 is a diagram showing the cross-sectional shape of the layered weld bead 70. In Fig. 6, the weld bead 70 is layered in a layering direction (height direction) that is approximately perpendicular to the base material 80.

[0037] Fig. 6(A) is a comparative example showing the cross-sectional shape of a weld bead 70 formed when DC of only EP polarity is supplied to the consumable electrode wire 51. Fig. 6(B) is a diagram showing the cross-sectional shape of a weld bead 70 formed when AC with a frequency of 2 Hz is supplied to the consumable electrode wire 51. Fig. 6(C) is a diagram showing the cross-sectional shape of a weld bead 70 formed when AC with a frequency of 30 Hz is supplied to the consumable electrode wire 51.

[0038] 6A, when the weld bead 70 is layered using a direct current, the temperature of the molten part increases with increasing height, and the shape of the weld bead 70 becomes unstable due to melting through of the weld bead 70. Thus, a direct current is not suitable for layering the weld bead 70.

[0039] 6(B) and 6(C), AC current reduces deformation due to burn-through compared to DC current. Under these conditions, the higher the EN ratio, the better the bead shape. However, in reality, if the weld bead 70 is sufficiently cooled, an EN ratio that is too high reduces the heat input to the weld bead 70, resulting in an excessively small molten portion and an unstable shape of the weld bead 70. Therefore, it is desirable to be able to select an appropriate EN ratio according to the state of the weld bead 70.

[0040] At a frequency of 2 Hz, if the short-circuit-arc cycle is 10 ms, the number of short-circuit-arc cycles in one AC cycle is 50, and the EN ratio adjustment unit is 2%. As an example, FIG. 6B shows five cross-sectional shapes: 20%, 30%, 50%, 70%, and 80%. As shown in FIG. 6B, the EN ratio can be finely adjusted (by reducing the adjustment unit), allowing the layer shape to be adjusted. Thus, an AC current with a frequency of 2 Hz is suitable for layering the weld bead 70.

[0041] At a frequency of 30 Hz, assuming the same short-circuit-arc cycle of 10 ms, the number of short-circuit-arc cycles per AC cycle is 3 to 4, and the EN ratio adjustment unit is approximately 25 to 33%. Figure 6(C) also shows changes in the short-circuit-arc cycle, and shows cross-sectional shapes for EN ratios of 20%, 50%, and 80% that can be selected under these conditions. As shown in Figure 6(C), although the EN ratio change unit becomes larger, the layer shape can be adjusted. Thus, AC with a frequency of 30 Hz is suitable for layering the weld bead 70.

[0042] As a result of the verification, the AC frequency appropriate for stacking was found to be as follows. FIG. 7 is a diagram for explaining the appropriate frequency range according to the first embodiment. When the AC frequency was less than 2 Hz, the EP period or EN period became longer and the heat input was not uniform, as shown in FIGS. 3(A) and 4. Therefore, as shown in FIG. 7, when the AC frequency was less than 2 Hz, the stability in the stacking direction was low.

[0043] When the AC frequency exceeds 30 Hz, the period of one AC cycle becomes shorter, which significantly reduces the number of times the EN ratio can be changed, as shown in Figures 3(B) and 3(C). Therefore, as shown in Figure 7, when the AC frequency exceeds 30 Hz, the adjustment unit of the EN ratio becomes too large, making it unsuitable for adjusting the stack shape by changing the EN ratio.

[0044] From the above, the optimum frequency of the AC current for lamination is a value between 2 Hz and 30 Hz. By controlling the AC frequency to a value between 2 Hz and 30 Hz, the control device 30 stably laminates the weld bead 70 when using the consumable electrode wire 51.

[0045] The process executed by the control device 30 according to the first embodiment will be described in detail. Fig. 8 is a flowchart showing the control content according to the first embodiment. The process of the flowchart in Fig. 8 is repeatedly called as a subroutine from the main routine in the control of the control device 30 and executed. First, in step S (hereinafter simply referred to as "S") 1, the control device 30 checks the stacking data stored in advance in the storage device 33.

[0046] Next, the control device 30 sets the welding conditions as shown in FIG. 5 (S2). Next, the control device 30 sets the AC frequency and EN ratio corresponding to the layer data of S1 and the welding conditions of S2 (S3). In S3, the control device 30 sets the AC frequency to a value between 2 Hz and 30 Hz. The AC frequency and EN ratio may be directly input by the user via an input unit such as a touch panel or keyboard (not shown), or the calculation device 31 may calculate appropriate values. The AC frequency and EN ratio may be extracted from predetermined data by the control device 30.

[0047] Next, the control device 30 transmits information on the AC frequency, EN ratio, current, and voltage to the welding power source 10 (S4). Next, the control device 30 transmits information on the wire feed speed to the wire feeder 50 (S5). Next, the control device 30 transmits the welding speed information to the robot arm 40 (S6), and the process returns from the subroutine to the main routine. Note that part or all of the control device 30 may be incorporated into the control device of the welding power source 10 or the robot arm 40.

[0048] In the additive manufacturing system 1 of the first embodiment, the control device 30 sets the AC frequency to a value of 2 Hz or more and 30 Hz or less. As shown in FIG. 7 , stability in the stacking direction is improved when the AC frequency is in the range of 2 Hz or more and 30 Hz or less. The EN ratio can be finely adjusted in the range of 2 Hz or more and 30 Hz or less. As a result, the additive manufacturing system 1 of the present disclosure can finely adjust the EN ratio while ensuring stability in the stacking direction, thereby enabling stable stacking of the weld bead 70 when using the consumable electrode wire 51.

[0049] [Embodiment 2] Next, a description will be given of an additive manufacturing system 1A according to embodiment 2. Fig. 9 is a diagram schematically illustrating the additive manufacturing system 1A according to embodiment 2. The additive manufacturing system 1A according to embodiment 2 differs from the additive manufacturing system 1 according to embodiment 1 in that it includes a detection device 61.

[0050] The detection device 61 is, for example, a shape sensor. When the weld bead 70 is being layered, the shape sensor (detection device 61) detects the shape of the weld bead 70 at a position H just before the layering in the welding direction indicated by the arrow in FIG. 9 . The shape sensor (detection device 61) is preferably a non-contact sensor such as a laser scanner. Position H corresponds to the layer (also referred to as the previous layer) that was layered immediately before the currently layered layer. The shape sensor (detection device 61) transmits height information of the weld bead 70 to the control device 30 as shape information of the weld bead 70.

[0051] The control device 30 controls at least one of the frequency of the AC current and the EN ratio in accordance with height information of the weld bead 70 received from the shape sensor (detection device 61). For example, the control device 30 executes the following process. If the stack height of the previous layer is high, the control device 30 decreases the EN ratio so that the currently stacked layer becomes lower. If the stack height of the previous layer is low, the control device 30 increases the EN ratio so that the currently stacked layer becomes higher. If the stack height of the previous layer is unstable, the control device 30 increases the frequency so that the currently stacked layer becomes stable. If it is desired to change the EN ratio in finer increments from the stack height of the previous layer, the control device 30 decreases the frequency so that the adjustment range of the EN ratio becomes narrower.

[0052] The detection device 61 may be, for example, a temperature sensor. When the weld bead 70 is being layered, the temperature sensor (detection device 61) detects the temperature of the weld bead 70 at a position H just before the layering in the welding direction indicated by the arrow in FIG. 9 . The temperature sensor (detection device 61) is preferably a non-contact sensor such as a thermal camera. Temperature information of the weld bead 70 detected by the temperature sensor (detection device 61) is transmitted to the control device 30. The temperature sensor (detection device 61) may be a pyrometer that takes images at a point rather than a thermal camera that takes images over an area.

[0053] The control device 30 controls at least one of the frequency of the AC and the EN ratio in accordance with the temperature information of the weld bead 70 received from the temperature sensor (detection device 61). For example, the control device 30 executes the following process: When the temperature of the previous layer is high, the control device 30 increases the EN ratio so that the temperature of the currently stacked layer decreases. When the temperature of the previous layer is low, the control device 30 decreases the EN ratio so that the temperature of the currently stacked layer increases.

[0054] The detection device 61 may include both a shape sensor and a temperature sensor. The control device 30 controls at least one of the frequency of the AC current and the EN ratio based on the information obtained from the detection device 61, thereby performing stacking according to the state of the previous layer.

[0055] [Modification] In the above embodiment, welding torch 20 may be moved by a Cartesian robot instead of by articulated robot arm 40 .

[0056] [Summary] (1) The present disclosure relates to an additive manufacturing system 1 that uses a consumable electrode arc welding method with short-circuit transfer to supply a welding current to a consumable electrode wire 51 and build up a weld bead 70 to manufacture a shaped object. The additive manufacturing system 1 includes a welding torch 20 that builds up the weld bead 70 using the consumable electrode wire 51, a drive device (robot arm 40) that moves the welding torch 20, a welding power source 10 that supplies AC current to the consumable electrode wire 51 as the welding current, and a control device 30 that controls the AC frequency and EN ratio. The EN ratio change period is constant regardless of the AC frequency. The control device 30 sets the AC frequency to a value between 2 Hz and 30 Hz.

[0057] According to the additive manufacturing system 1 of the present disclosure, the control device 30 sets the AC frequency to a value of 2 Hz or more and 30 Hz or less. Stability in the stacking direction is improved when the AC frequency is in the range of 2 Hz or more and 30 Hz or less. The EN ratio can be finely adjusted in the range of 2 Hz or more and 30 Hz or less. This allows the additive manufacturing system 1 of the present disclosure to finely adjust the EN ratio while ensuring stability in the stacking direction, thereby enabling stable stacking of the weld bead 70 when using the consumable electrode wire 51.

[0058] (2) In the additive manufacturing system 1 of (1), the adjustment unit of the EN ratio (e.g., 2%) when the AC frequency is a first frequency (e.g., 2 Hz) is set to be smaller than the adjustment unit of the EN ratio (e.g., 25% to 33%) when the AC frequency is a second frequency (e.g., 30 Hz) that is higher than the first frequency.

[0059] According to the additive manufacturing system 1 of the present disclosure, the unit of adjustment of the EN ratio can be adjusted by changing the frequency of the AC, thereby adjusting the unit of change of the EN ratio.

[0060] (3) In the additive manufacturing system 1 of (1) or (2), the control device 30 increases the EN ratio when the build height of the weld bead 70 is increased.

[0061] According to the additive manufacturing system 1 of the present disclosure, the stacking height can be easily increased by increasing the EN ratio.

[0062] (4) The additive manufacturing system 1A according to any one of (1) to (3) further includes a shape sensor (detection device 61) that detects the shape of the weld bead 70 before being layered when layering the weld bead 70. The control device 30 controls at least one of the frequency of the AC and the EN ratio according to the shape of the weld bead 70 detected by the shape sensor (detection device 61).

[0063] According to the additive manufacturing system 1A of the present disclosure, stacking can be performed according to the shape of the weld bead 70 before stacking, which is detected by the shape sensor (detection device 61).

[0064] (5) The additive manufacturing system 1A according to any one of (1) to (4) further includes a temperature sensor (detection device 61) that detects the temperature of the weld bead 70 immediately before it is stacked when stacking the weld bead 70. The control device 30 controls at least one of the frequency of the AC and the EN ratio according to the temperature of the weld bead 70 detected by the temperature sensor (detection device 61).

[0065] According to the additive manufacturing system 1A of the present disclosure, it is possible to perform stacking in accordance with the temperature of the weld bead 70 before stacking, detected by the temperature sensor (detection device 61).

[0066] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The 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.

[0067] 1, 1A Additive manufacturing system, 10 Welding power source, 20 Welding torch, 21 Nozzle, 30 Control device, 31 Arithmetic unit, 32 Memory, 33 Storage device, 34 Input / output interface, 40 Robot arm, 50 Wire feeder, 51 Consumable electrode wire, 61 Detection device, 70 Weld bead, 80 Base material, 330 Control program.

Claims

1. An additive manufacturing system that uses a consumable electrode arc welding method with short-circuit transfer to supply a welding current to a consumable electrode wire and build up a weld bead to form a model, comprising: a welding torch that builds up the weld bead using the consumable electrode wire; a drive device that moves the welding torch; a welding power source that supplies AC to the consumable electrode wire as the welding current; and a control device that controls the frequency and EN ratio of the AC, wherein the change cycle of the EN ratio is constant regardless of the AC frequency, and the control device sets the AC frequency to a value between 2 Hz and 30 Hz.

2. An additive manufacturing system as described in claim 1, wherein the adjustment unit of the EN ratio when the frequency of the AC is a first frequency is set to be smaller than the adjustment unit of the EN ratio when the frequency of the AC is a second frequency higher than the first frequency.

3. An additive manufacturing system according to claim 1 or claim 2, wherein the control device increases the EN ratio when the build height of the weld bead is increased.

4. An additive manufacturing system as described in claim 1 or claim 2, further comprising a shape sensor that detects the shape of the weld bead before it is stacked when the weld bead is stacked, and the control device controls at least one of the frequency of the AC and the EN ratio according to the shape of the weld bead detected by the shape sensor.

5. An additive manufacturing system as described in claim 1 or claim 2, further comprising a temperature sensor that detects the temperature of the weld bead just before it is stacked when the weld bead is stacked, and the control device controls at least one of the frequency of the AC and the EN ratio according to the temperature of the weld bead detected by the temperature sensor.

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