Additive manufacturing system

Abstract

This additive manufacturing system (1) is provided with: a welding torch (20); a robot arm (40); a temperature sensor (61); a welding power source (10) that supplies an alternating current to a consumable electrode wire (51) as a welding current; and a control device (30) that controls the EN ratio of the alternating current. The control device (30) calculates, according to the temperature of weld beads (70) detected by the temperature sensor (61), an appropriate EN ratio for laminating the weld beads (70).

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 technology for forming a shaped object by stacking weld beads, and also discloses that the welding conditions are changed when the height of the weld bead deviates from the planned height.

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

[0004] In Japanese Patent Laid-Open Publication No. 2022-106172 (Patent Document 1), a consumable electrode is used to build up the weld bead, and the welding speed is changed depending on the build-up height. It also states that other factors besides the welding speed can be the filler wire feed speed or the heat input for generating the arc. However, while non-consumable electrode arc welding allows for the wire feed speed as the filler metal and the value of the welding current as the heat input to be controlled separately, this is difficult to control separately in consumable electrode arc welding.

[0005] In a consumable electrode welding system, the wire feed rate and the wire melting rate are equal, resulting in stable welding. The wire feed rate and the wire melting rate have a one-to-one relationship with the welding current and cannot be set individually. In other words, Japanese Patent Laid-Open Publication No. 2022-106172 (Patent Document 1) does not take into account the use of a consumable electrode, so if the height of the weld bead deviates from the planned height, it is not possible to change to optimal welding conditions, and it is not sufficient to stably build up the weld bead.

[0006] An object of the present disclosure is to provide a technique that allows stable deposition of weld beads when using a consumable electrode wire.

[0007] The present disclosure relates to an additive manufacturing system that supplies a welding current to a consumable electrode wire and builds a weld bead to form a shaped object. The additive manufacturing system includes a welding torch that builds a weld bead using a consumable electrode wire, a drive device that moves the welding torch, a detection device that detects the temperature or shape of the weld bead before it is built up, a welding power source that supplies AC current to the consumable electrode wire as the welding current, and a control device that controls the EN ratio of the AC. The control device calculates an appropriate EN ratio for building up the weld bead based on at least one of the temperature and shape of the weld bead detected by the detection device.

[0008] The additive manufacturing system of the present disclosure calculates an appropriate EN ratio for depositing a weld bead based on at least one of the temperature and shape of the weld bead detected by the detection device. The deposition amount of the weld bead can be easily changed independently of the current by changing the EN ratio. This allows the additive manufacturing system of the present disclosure to stably deposit a weld bead when using a consumable electrode wire.

[0009] FIG. 1 is a diagram schematically illustrating an additive manufacturing system according to embodiment 1. FIG. 2 is a diagram for explaining an EN ratio. FIG. 3 is a diagram for explaining an example of the relationship between welding current and wire melting rate for each EN ratio. FIG. 4 is a diagram for explaining the relationship between the temperature of a weld bead and an EN ratio to be set. FIG. 5 is a flowchart showing control details according to embodiment 1. FIG. 6 is a diagram schematically illustrating an additive manufacturing system according to embodiment 2. FIG. 7 is a diagram for explaining an example of the relationship between welding current and wire melting rate for each EN ratio. FIG. 8 is a diagram for explaining the relationship between the height of a weld bead and an EN ratio to be set. FIG. 9 is a flowchart showing control details according to embodiment 2. FIG. 10 is a flowchart showing control details according to a modified example.

[0010] 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.

[0011] 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, a temperature sensor 61, and a control device 30.

[0012] 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.

[0013] In the welding torch 20, a welding current is supplied to a consumable electrode wire 51 by a power supply tip (not shown) located inside the nozzle 21. The consumable electrode wire 51 melts due to resistance heating caused by the current flow and an arc 22 generated between the consumable electrode wire 51 and the base material 80 or an already deposited weld bead 70. 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 is supplied to the welding torch 20 by a shielding gas supply unit (not shown), and the shielding gas emerges from the nozzle 21 and reaches the arc 22 and the weld zone. Examples of the shielding gas that can be used include argon, CO2, and mixtures containing these.

[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] 2 is a diagram illustrating the EN ratio. Welding power supply 10 switches between electrode positive polarity and electrode negative polarity supplied to consumable electrode wire 51 in welding torch 20. Electrode positive polarity refers to a polarity state in which the consumable electrode wire 51 side of the current path supplied from welding power supply 10 is the anode and the base material 80 or weld bead 70 side is the cathode. Electrode negative polarity refers to a polarity state in which the base material 80 or weld bead 70 side of the current path supplied from welding power supply 10 is the anode and the consumable electrode wire 51 side is the cathode.

[0016] For example, in the case of the pulse waveform shown in Fig. 2, the ratio of the electrode positive polarity to the total of the electrode positive polarity and the electrode negative polarity is called the EP ratio, and the ratio of the electrode negative polarity is called the EN ratio. As shown in Fig. 2, the welding power source 10, for example, has a positive electrode polarity (S ＥＰ ) and electrode negative polarity (S ＥＮ ) can be output. The EN ratio can be set in a similar manner not for a pulse waveform but for a waveform for short-circuit welding with short-circuit transition.

[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 increases during periods of electrode negative polarity, and the amount of heat input from the arc 22 to the base material 80 or weld bead 70 increases during periods of electrode positive polarity. Therefore, the wire melting rate can be adjusted by the EN ratio.

[0018] The heat input from the arc 22 to the fusion zone can also be increased by increasing the amplitude of the welding current in Fig. 2. However, if the heat input to the fusion zone increases too much due to an increase in the welding current, the state of the weld bead 70 becomes unstable, causing burn-through. Therefore, the control device 30 controls the magnitude of the welding current output by the welding power source 10 and the EN ratio to keep the state of the weld bead 70 appropriate for layering.

[0019] 1 , wire feeder 50 includes a roller and a motor (not shown). Wire feeder 50 drives the motor to rotate the roller, thereby feeding consumable electrode wire 51 to welding torch 20.

[0020] Temperature sensor 61 functions as a detection device that detects the temperature of weld bead 70 at position T just before lamination in the welding direction indicated by the arrow in FIG. 1 when laminating weld bead 70. Temperature sensor 61 is preferably a non-contact sensor such as a thermal camera. Position T corresponds to the layer (previous layer) laminated immediately before the currently laminated layer. Temperature information of weld bead 70 detected by temperature sensor 61 is transmitted to control device 30. Temperature sensor 61 may be a pyrometer that captures images at a point rather than a thermal camera that captures images over a surface.

[0021] Here, in an object formed by stacking weld beads 70, the lower layers are closer to the base material 80 and therefore heat escapes more easily, while the upper layers are further from the base material 80 and therefore heat escapes less easily. In such a case, if welding current is supplied to the consumable electrode wire 51 under the same welding conditions, the amount of heat in the weld beads 70 in the upper layers may become too high, causing the weld beads 70 to melt through. The additive manufacturing system 1 according to the first embodiment changes the welding conditions based on the temperature information of the weld beads 70 detected by the temperature sensor 61.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The storage device 33 functions as a storage unit that stores various programs or 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.

[0026] Values ​​acquired by temperature sensor 61 and the like are input to input / output interface 34. Control device 30 sets the welding current to be output by welding power source 10 in accordance with the temperature information acquired from temperature sensor 61. Specifically, control device 30 calculates the EN ratio in accordance with the temperature of weld bead 70 detected by temperature sensor 61, and calculates the welding current to be set in welding power source 10 from the calculated EN ratio.

[0027] Next, the relationship between the welding current and the wire melting rate will be described. Fig. 3 is a diagram illustrating an example of the relationship between the welding current and the wire melting rate for each EN ratio. In Fig. 3, the horizontal axis represents the welding current, and the vertical axis represents the wire melting rate. The wire melting rate is the rate at which the consumable electrode wire 51 melts and turns into a weld bead 70. As shown in Fig. 3, the wire melting rate increases as the welding current increases.

[0028] In order to stably build up the weld bead 70, it is important to maintain a constant wire melting rate to maintain a constant amount of weld bead 70 formed. Also, in order to stably build up the weld bead 70, it is important to maintain a constant temperature of the weld bead 70 (melt zone). Thus, to stably build up the weld bead 70, welding conditions are required that maintain a constant wire melting rate and a constant net heat input, which is the heat input to the melt zone minus the heat output from the melt zone. Because the wire melting rate cannot be directly controlled, the control device 30 indirectly adjusts the wire melting rate by sending a command to the wire feeder 50 to adjust the wire feed speed.

[0029] For example, if the temperature of the previous layer is high, it is assumed that the amount of heat transferred from the weld bead 70 (fusion zone) to the previous layer will be small, so it is possible to reduce the heat input by current flow to maintain a constant net heat input to the fusion zone. However, in the case of consumable electrodes, as shown in Figure 3, there is a positive correlation between the welding current and the wire melting rate. Therefore, if we consider only a simple DC current (EN ratio 0%), reducing the current will also reduce the wire melting rate, making it impossible to maintain a constant wire melting rate. Therefore, we consider reducing the current by adjusting the EN ratio using AC current to maintain a constant wire melting rate and maintain a constant net heat input to the fusion zone.

[0030] 3 shows an example of the relationship between the welding current and the melting rate of the consumable electrode wire 51 for each EN ratio. As shown in Fig. 3, the relationship between the welding current and the wire melting rate is such that, when the wire melting rate of the consumable electrode wire 51 is constant at V0, the welding current decreases from I1 to I3 as the EN ratio increases. In other words, it can be seen that by keeping the wire melting rate constant at V0, the arc heat input can be changed by adjusting the EN ratio and changing the magnitude of the welding current so that the net heat input remains constant while the deposition amount remains constant.

[0031] Next, the EN ratio to be set in accordance with the temperature of the weld bead 70 will be described. Fig. 4 is a diagram for explaining the relationship between the temperature of the weld bead 70 and the set EN ratio. In Fig. 4, the horizontal axis represents the temperature of the weld bead 70, and the vertical axis represents the set EN ratio. As shown in Fig. 4, the EN ratio is set to increase as the temperature of the weld bead 70 increases.

[0032] In Fig. 4, in order to maintain a constant deposition amount, an EN ratio is set to adjust the heat input by changing the magnitude of the welding current while keeping the wire melting rate constant, as in the correspondence relationship in Fig. 3. Specifically, when the temperature of the weld bead 70 of the previous layer is high, a correspondence relationship is set such that a high EN ratio is set so that the welding current is reduced in order to reduce the heat input from the arc 22 to the weld bead 70. Conversely, when the temperature of the weld bead 70 of the previous layer is low, a correspondence relationship is set such that a low EN ratio is set so that the welding current is increased in order to increase the heat input from the arc 22 to the weld bead 70. Using the correspondence relationship in Fig. 4, an appropriate EN ratio is calculated depending on the temperature of the weld bead 70.

[0033] As shown in Fig. 4, an appropriate EN ratio is set for layering the weld bead 70 depending on the temperature of the weld bead 70 of the previous layer. Then, as shown in Fig. 3, by changing the EN ratio depending on the temperature of the weld bead 70 of the previous layer while keeping the wire melting rate constant, the magnitude of the welding current can be adjusted to keep the heat input to the molten part constant. This allows the weld bead 70 to be layered stably.

[0034] The relationships shown in Figures 3 and 4 are stored in advance in storage device 33 based on experiments or the like. The correspondence relationships shown in Figures 3 and 4 are just examples, and information on a plurality of correspondence relationships according to the types of consumable electrode wires 51 to be laminated may be stored in storage device 33. The correspondence relationships shown in Figures 3 and 4 may also be determined by calculations or the like rather than by experiments.

[0035] Next, the processing executed by the control device 30 according to the first embodiment will be described in detail. FIG. 5 is a flowchart showing the control content according to the first embodiment. The processing of the flowchart in FIG. 5 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") 11, the control device 30 determines whether or not it has acquired temperature information of the weld bead 70 transmitted from the temperature sensor 61. The temperature information may be transmitted, for example, at regular intervals. If the control device 30 determines that it has not acquired temperature information (NO in S11), it returns the processing from the subroutine to the main routine.

[0036] If the control device 30 determines that it has acquired temperature information (YES in S11), it calculates the EN ratio corresponding to the temperature information of the weld bead 70 detected by the temperature sensor 61 based on the correspondence relationship shown in FIG. 4 stored in the memory device 33 (S12). Next, the control device 30 calculates the welding current corresponding to the EN ratio calculated in S12 when the melting rate of the consumable electrode wire 51 is constant based on the correspondence relationship shown in FIG. 3 stored in the memory device 33 (S13). By performing the process in S13, the control device 30 can calculate the optimal welding current by changing the EN ratio while maintaining a constant melting rate (constant wire feed speed) in accordance with the temperature information of the weld bead 70. Next, the control device 30 transmits information regarding the welding current magnitude and the EN ratio to the welding power source 10 (S14), and the process returns from the subroutine to the main routine. The EN ratio and the welding current may be calculated directly in the welding power source 10. In this manner, part or all of the control device 30 may be incorporated into the welding power source 10 or the control device of the robot arm 40.

[0037] In the additive manufacturing system 1 of the first embodiment, the control device 30 calculates an appropriate EN ratio for depositing the weld bead 70 in accordance with the temperature of the weld bead 70 detected by the temperature sensor 61. The control device 30 then calculates the welding current to be set in the welding power source 10 from the calculated EN ratio. By calculating the welding current to be set in the welding power source 10 from the EN ratio in this manner, the weld bead 70 can be stably deposited when using the consumable electrode wire 51. The welding power source 10 outputs a current waveform corresponding to the EN ratio and the welding current.

[0038] The control device 30 calculates the EN ratio corresponding to the temperature of the weld bead 70 detected by the temperature sensor 61 from the correspondence relationship shown in Fig. 4 stored in the storage device 33. The control device 30 calculates the magnitude of the welding current corresponding to the EN ratio when the melting rate of the consumable electrode wire 51 is constant (the wire feed speed is constant) from the correspondence relationship shown in Fig. 3 stored in the storage device 33. This allows the magnitude of the welding current to be changed while keeping the melting rate of the consumable electrode wire 51 constant based on the EN ratio that is optimal for the temperature of the weld bead 70, thereby enabling deposition with a constant deposition amount of the weld bead 70. By setting the welding current in this way, the additive manufacturing system 1 can stabilize deposition while preventing burn-through of the weld bead 70.

[0039] [Embodiment 2] Next, an additive manufacturing system 1A according to embodiment 2 will be described. Fig. 6 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 a shape sensor 62 is provided instead of a temperature sensor 61.

[0040] When the weld bead 70 is being layered, the shape sensor 62 functions as a detection device that detects the shape of the weld bead 70 at a position T just before the layering in the welding direction indicated by the arrow in Figure 7. The shape sensor 62 is preferably a non-contact sensor such as a laser scanner. Position T corresponds to the layer (previous layer) layered immediately before the currently layered layer. The shape sensor 62 transmits height information of the weld bead 70 to the control device 30 as shape information of the weld bead 70.

[0041] Next, the relationship between the welding current and the wire melting rate for each EN ratio will be described. Fig. 7 is a diagram for explaining an example of the relationship between the welding current and the wire melting rate for each EN ratio. In Fig. 7, the horizontal axis represents the welding current, and the vertical axis represents the wire melting rate. As shown in Fig. 7, the wire melting rate increases as the welding current increases.

[0042] In order to stably build up the weld bead 70, it is important to keep the heat input to the fusion zone constant by keeping the welding current constant. Also, in order to stably build up the weld bead 70, it is important to keep the amount of weld bead 70 formed constant by changing the wire melting rate of the weld bead 70 in accordance with the shape of the weld bead 70 of the previous layer. Thus, in order to stably build up the weld bead 70, the welding conditions required are to keep the heat input to the fusion zone constant and to keep the amount of weld bead 70 formed constant by changing the wire melting rate.

[0043] For example, if the height of the previous layer is low, it is possible to increase the wire melting rate while keeping the heat input to the fusion zone constant. However, in the case of a consumable electrode, as shown in Figure 7, there is a positive correlation between the welding current and the wire melting rate. Therefore, if we consider only a simple DC current (EN ratio 0%), increasing the wire melting rate will also increase the welding current, making it impossible to maintain a constant heat input to the fusion zone. Therefore, we consider changing the wire melting rate while keeping the heat input to the fusion zone constant by adjusting the EN ratio using AC current.

[0044] 7, the relationship between the welding current and the melting rate of the consumable electrode wire 51 is defined for each EN ratio. As shown in Fig. 7, the relationship between the welding current and the wire melting rate is such that, when the welding current is constant at I0, the wire melting rate of the consumable electrode wire 51 increases from V1 to V3 as the EN ratio increases. In other words, in order to stably build up the weld bead 70, it is sufficient to change the EN ratio and change the wire melting rate while keeping the heat input constant by keeping the welding current constant at I0.

[0045] Next, the relationship between the height of the weld bead 70 and the EN ratio will be described. Figure 8 is a diagram for explaining the relationship between the height of the weld bead 70 and the set EN ratio. In Figure 8, the horizontal axis represents the height of the weld bead 70, and the vertical axis represents the set EN ratio. As shown in Figure 8, the EN ratio is set to decrease as the height of the weld bead 70 increases.

[0046] In Fig. 8, in order to maintain a constant heat input, the EN ratio is set to adjust the deposition amount by changing the wire melting rate while keeping the welding current constant, as in the correspondence relationship in Fig. 7. Specifically, when the height of the weld bead 70 of the previous layer is high, the correspondence relationship is set to a low EN ratio so that the wire melting rate is slowed to reduce the deposition amount. Conversely, when the height of the weld bead 70 of the previous layer is low, the correspondence relationship is set to a high EN ratio so that the wire melting rate is increased to increase the deposition amount. Using the correspondence relationship in Fig. 8, an appropriate EN ratio is calculated depending on the height of the weld bead 70.

[0047] As shown in Fig. 8, an appropriate EN ratio is set for layering the weld bead 70 depending on the height of the weld bead 70 of the previous layer. Then, as shown in Fig. 7, by changing the EN ratio depending on the height of the weld bead 70 of the previous layer while keeping the welding current constant, it is possible to adjust the wire melting rate while maintaining a constant heat input to the molten part and keeping the welding current constant. This allows the weld bead 70 to be layered stably.

[0048] 7 and 8 are stored in advance in storage device 33 based on experiments, etc. The correspondence relationships shown in Figures 7 and 8 are just examples, and information on a plurality of correspondence relationships may be stored in storage device 33 according to the types of consumable electrode wires 51 to be laminated.

[0049] Next, the processing executed by the control device 30 according to the second embodiment will be described in detail. FIG. 9 is a flowchart showing the control content according to the second embodiment. The processing of the flowchart in FIG. 9 is repeatedly called as a subroutine from the main routine in the control of the control device 30 and executed. First, in step S21, the control device 30 determines whether height information of the weld bead 70 has been acquired as shape information of the weld bead 70 transmitted from the shape sensor 62. The height information may be transmitted at regular intervals, for example. If the control device 30 determines that shape information has not been acquired (NO in S21), the control device 30 returns the processing from the subroutine to the main routine.

[0050] When the control device 30 determines that the height information has been acquired (YES in S21), it calculates the EN ratio corresponding to the height information of the weld bead 70 detected by the shape sensor 62 based on the correspondence relationship shown in Fig. 8 stored in the storage device 33 (S22). Next, the control device 30 calculates the melting rate of the consumable electrode wire 51 corresponding to the EN ratio calculated in S22 when the welding current is constant based on the correspondence relationship shown in Fig. 7 stored in the storage device 33 (S23). By performing the process in S23, the control device 30 can calculate the optimal wire melting rate by changing the EN ratio in accordance with the height information of the weld bead 70 while keeping the magnitude of the welding current constant.

[0051] Next, control device 30 transmits information regarding the magnitude of the welding current and the EN ratio to welding power source 10 (S24). Next, control device 30 transmits information regarding the wire melting rate of consumable electrode wire 51 to wire feeder 50 (S25), and returns the process from the subroutine to the main routine. Wire feeder 50 adjusts the wire feed rate to match the wire melting rate.

[0052] In the additive manufacturing system 1A of the second embodiment, the control device 30 calculates an appropriate EN ratio for layering the weld bead 70 in accordance with the height of the weld bead 70 detected by the shape sensor 62. The control device 30 then adjusts the wire melting rate by setting the wire feed rate to be set in the wire feeder 50 based on the calculated EN ratio. This allows the amount of welding to be adjusted while maintaining a constant heat input by changing the wire melting rate while maintaining a constant magnitude of the welding current based on the EN ratio that is optimal for the height of the weld bead 70.

[0053] The control device 30 calculates the EN ratio corresponding to the height of the weld bead 70 detected by the shape sensor 62 from the correspondence relationship shown in Fig. 8 stored in the storage device 33. The control device 30 calculates the melting rate of the consumable electrode wire 51 corresponding to the EN ratio when the welding current is constant from the correspondence relationship shown in Fig. 7 stored in the storage device 33. This allows the welding current to be kept constant while the wire melting rate is changed based on the EN ratio that is optimal for the height of the weld bead 70, thereby enabling deposition to be performed in which the deposition amount of the weld bead 70 is adjusted while maintaining a constant heat input. By setting the welding current and the feed rate of the consumable electrode wire 51 in the wire feeder 50 in this way, the additive manufacturing system 1A can stabilize deposition while preventing burn-through of the weld bead 70.

[0054] [Modification] Next, a process executed by the control device 30 according to a modification will be described in detail. FIG. 10 is a flowchart showing the control process according to the modification. The process of the flowchart in FIG. 10 is repeatedly called as a subroutine from the main routine of the control of the control device 30 and executed. In step S31, the control device 30 first determines whether size information of the weld pool has been acquired as shape information of the weld bead 70 transmitted from the shape sensor 62. The size information of the weld pool is information regarding the size of the molten metal puddle when the consumable electrode wire 51 melts. The memory device 33 stores a correspondence relationship between the size of the weld pool and approximate temperature information of the weld bead 70. This correspondence relationship is determined in advance through experiments or the like and stored in the memory device 33.

[0055] If the control device 30 determines that the weld pool size information has not been acquired (NO in S31), it returns the process from the subroutine to the main routine. If the control device 30 determines that the weld pool size information has been acquired (YES in S31), it calculates the temperature information of the weld bead 70 corresponding to the weld pool size information stored in the memory device 33 (S32). Next, the control device 30 calculates the EN ratio corresponding to the temperature information of the weld bead 70 (S33). Next, the control device 30 calculates the welding current corresponding to the EN ratio calculated in S33 when the melting rate of the consumable electrode wire 51 is constant (the wire feed speed is constant) (S34). Next, the control device 30 transmits information regarding the magnitude of the welding current and the EN ratio to the welding power source 10 (S35), and returns the process from the subroutine to the main routine.

[0056] As shown in the modified example, by indirectly determining the temperature information of the weld bead 70 from the size of the molten pool, it is possible to stably build up the weld bead 70 even when it is difficult to measure the temperature. Note that the size of the molten pool may be directly associated with an EN ratio that is optimal for that size of the molten pool, without converting it into temperature information, and control may be performed.

[0057] The additive manufacturing system 1 may be configured to include both the temperature sensor 61 and the shape sensor 62. In such a case, the EN ratio corresponding to the temperature information and the shape information may be calculated.

[0058] In the above embodiment, the temperature information or shape information of the weld bead 70 may be acquired for each layer in the stacking of the shaped object.

[0059] In the above embodiment, a driving device for individually moving the detection device may be provided. The driving device may be controlled to move the detection device to an appropriate position in response to the operation of the welding torch 20.

[0060] In the above embodiment, the welding torch 20 may be moved by a Cartesian robot instead of the articulated robot arm 40 .

[0061] <Summary> (1) The present disclosure relates to an additive manufacturing system 1 that supplies a welding current to a consumable electrode wire 51 and builds up a weld bead 70 to form 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 detection device (temperature sensor 61) that detects the temperature or shape of the weld bead 70 just before it is built up, 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 EN ratio of the AC. The control device 30 calculates an appropriate EN ratio for building up the weld bead 70 based on at least one of the temperature and the shape of the weld bead 70 detected by the detection device (temperature sensor 61).

[0062] According to the additive manufacturing system 1 of the present disclosure, the control device 30 calculates an appropriate EN ratio for depositing the weld bead 70 based on at least one of the temperature and shape of the weld bead 70 detected by the detection device (temperature sensor 61). The deposition amount of the weld bead 70 can be easily changed independently of the current by changing the EN ratio. This allows the additive manufacturing system 1 of the present disclosure to stably deposit the weld bead 70 when using a consumable electrode wire 51.

[0063] (2) The additive manufacturing system 1 of (1) further includes a memory unit (storage device 33) that stores a first correspondence relationship that defines the relationship between the temperature of the weld bead 70 and the EN ratio, and a second correspondence relationship that defines, for each EN ratio, the relationship between the welding current and the melting rate of the consumable electrode wire 51. The control device 30 calculates, from the first correspondence relationship, a first EN ratio that corresponds to the temperature of the weld bead 70 detected by the detection device (temperature sensor 61), and calculates, from the second correspondence relationship, a welding current that corresponds to the first EN ratio when the melting rate of the consumable electrode wire 51 is constant.

[0064] According to the additive manufacturing system 1 of the present disclosure, it is possible to perform layering while maintaining a constant melting rate of the consumable electrode wire 51 based on the EN ratio that is optimal for the temperature of the weld bead 70 .

[0065] (3) In the additive manufacturing system 1 of (1) or (2), the first correspondence relationship is a relationship in which the EN ratio increases as the temperature of the weld bead 70 increases.

[0066] According to the additive manufacturing system 1 of the present disclosure, it is possible to calculate the optimal EN ratio according to the first correspondence relationship.

[0067] (4) In the additive manufacturing system 1 described in any one of (1) to (3), the second correspondence relationship is a relationship in which, when the melting rate of the consumable electrode wire 51 is constant, the welding current decreases as the EN ratio increases.

[0068] According to the additive manufacturing system 1 of the present disclosure, it is possible to calculate an appropriate welding current from the EN ratio when the melting rate of the consumable electrode wire 51 is constant.

[0069] (5) In the additive manufacturing system 1A of (1), the detection device (shape sensor 62) is capable of detecting the shape of the weld bead 70 immediately before being layered as height information when the weld bead 70 is layered. The system further includes a memory unit (storage device 33) that stores a third correspondence relationship that defines the relationship between the height information and the EN ratio and a second correspondence relationship that indicates the relationship between the welding current and the melting rate of the consumable electrode wire 51 for each EN ratio. The control device 30 calculates the EN ratio corresponding to the height information detected by the detection device (shape sensor 62) from the third correspondence relationship, and calculates the melting rate of the consumable electrode wire 51 corresponding to the EN ratio when the welding current is constant from the second correspondence relationship.

[0070] The additive manufacturing system 1A of the present disclosure allows for layering while maintaining a constant welding current based on an EN ratio that is optimal for the height of the weld bead 70. Because the additive manufacturing system 1A can layer the weld bead 70 while maintaining a constant welding current, it is possible to stabilize layering while preventing burn-through.

[0071] (6) In the additive manufacturing system 1A in (5), the third correspondence relationship is a relationship in which the EN ratio decreases as the height of the weld bead 70 increases.

[0072] According to the additive manufacturing system 1A of the present disclosure, it is possible to calculate the optimal EN ratio according to the third correspondence relationship.

[0073] (7) In the additive manufacturing system 1A of (5) or (6), the second correspondence relationship is a relationship in which, when the welding current is constant, the melting rate of the consumable electrode wire 51 increases as the EN ratio increases.

[0074] According to the additive manufacturing system 1A of the present disclosure, the appropriate melting rate of the consumable electrode wire 51 when the welding current is constant can be calculated from the EN ratio.

[0075] 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.

[0076] 1, 1A Additive Manufacturing System, 10 Welding Power Source, 20 Welding Torch, 21 Nozzle, 22 Arc, 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 Temperature Sensor, 62 Shape Sensor, 70 Weld Bead, 80 Base Material, 330 Control Program.

Claims

1. An additive manufacturing system that supplies a welding current to a consumable electrode wire and builds 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 detection device that detects the temperature or shape of the weld bead just before it is built up when building up the weld bead; a welding power source that supplies AC to the consumable electrode wire as the welding current; and a control device that controls the EN ratio of the AC, wherein the control device calculates the EN ratio appropriate for building up the weld bead in accordance with at least one of the temperature and shape of the weld bead detected by the detection device.

2. The additive manufacturing system of claim 1, further comprising a memory unit that stores a first correspondence relationship that defines the relationship between the temperature of the weld bead and the EN ratio, and a second correspondence relationship that defines the relationship between the welding current and the melting rate of the consumable electrode wire for each EN ratio, wherein the control device calculates a first EN ratio that corresponds to the temperature of the weld bead detected by the detection device from the first correspondence relationship, and calculates the welding current that corresponds to the first EN ratio when the melting rate of the consumable electrode wire is constant from the second correspondence relationship.

3. The additive manufacturing system according to claim 2, wherein the first correspondence relationship is a relationship in which the EN ratio increases as the temperature of the weld bead increases.

4. The additive manufacturing system of claim 2, wherein the second correspondence relationship is such that, when the melting rate of the consumable electrode wire is constant, the welding current decreases as the EN ratio increases.

5. The additive manufacturing system of claim 1, wherein the detection device is capable of detecting the shape of the weld bead immediately before it is layered as height information when the weld bead is layered, and further comprises a memory unit that stores a third correspondence relationship that defines the relationship between the height information and the EN ratio, and a second correspondence relationship that indicates the relationship between the welding current and the melting rate of the consumable electrode wire for each EN ratio, and the control device calculates the EN ratio that corresponds to the height information detected by the detection device from the third correspondence relationship, and calculates the melting rate of the consumable electrode wire that corresponds to the EN ratio when the welding current is constant from the second correspondence relationship.

6. The additive manufacturing system according to claim 5, wherein the third correspondence relationship is a relationship in which the EN ratio decreases as the height of the weld bead increases.

7. The additive manufacturing system of claim 5, wherein the second correspondence relationship is such that, when the welding current is constant, the melting rate of the consumable electrode wire increases as the EN ratio increases.

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