Weld bead shape control method, power supply control method, stack molding method, control device, power supply device, welding system, stack molding system, and program

Abstract

A bead shape is controlled in which a forward feed period and a reverse feed period of a welding wire are periodically repeated as one cycle, and an arc period in which an arc is generated at the tip of a welding torch and a short-circuit period are provided within the period of one cycle. In the method for controlling the shape of the weld bead, the average feeding speed of the welding wire is kept constant, and the detection of the short-circuit time and the control of the peak current value are performed for each cycle of the feeding of the welding wire based on characteristic information in which the peak current value of the welding current and the short-circuit time are associated. The short-circuit time is converged within a target range determined by the characteristic information.

Description

Technical Field

[0001] The present invention relates to a method for controlling a weld bead shape, a power supply control method, a stacking modeling method, a control device, a power supply device, a welding system, a stacking modeling system and a program. Background Art

[0002] As a method of performing welding by moving the welding wire back and forth between the conductive tip and the molten pool and controlling the power supply to intermittently generate an arc, CMT (Cold Metal Transfer) welding is known. In this CMT welding, when the welding wire is formed into a molten droplet to form a weld bead, the separation of the molten droplet is promoted by reducing the current just before a short circuit and retracting the welding wire after the short circuit, and the welding current when the arc is re-ignited is controlled to a minimum. In this way, a droplet transfer with reduced spatter can be achieved. In addition, in CMT welding, the welding current is controlled synchronously with the forward and backward movement of the welding wire, the welding wire is fed into the molten pool when the arc is generated, and the welding wire is immediately retracted and the molten pool is cooled once a short circuit is detected, thereby reducing the heat input.

[0003] Such CMT welding technology is described in, for example, Patent Document 1. Patent Document 1 describes a power supply control method that assumes stacked molding, and in order to keep the welding speed constant, the feed speed of the welding wire is monitored, and the welding current, the free length of the welding wire, the distance between the conductive tip and the workpiece (the distance between the welding tip and the base material), etc. are adjusted to compensate for the shape deviation of the formed weld bead.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2021 / 219677 Summary of the invention

[0007] -Problems to be solved by the invention-

[0008] The above-mentioned CMT (Cold Metal Transfer) welding is a welding technology particularly suitable for joining thin plates. In order to ensure a constant penetration depth, the current waveform is set to a constant mode, and the short circuit between the conductive tip and the molten pool and the arc re-ignition are reliably performed, thereby achieving low heat input and low sputtering. However, in this CMT welding, if the distance between the welding tip and the base material changes, the timing of the feeding and retraction of the welding wire changes, so the average feed speed of the welding wire changes. The change in the average feed speed is not a problem in the welding of thin plates, but it is not preferred in cases where the repetitive stability of the process is strongly required, such as stacking molding, and the constant shape of the weld bead is desired.

[0009] The present invention solves the above-mentioned problems and aims to provide a method for controlling the shape of a weld bead, a power supply control method, a stacking modeling method, a control device, a power supply device, a welding system, a stacking modeling system and a program, which can keep the shape of the weld bead constant in real time without changing the average feed speed of the weld wire and independently of the distance between the welding tip and the base material even when welding is performed by repeatedly feeding and retracting the welding wire.

[0010] -Methods for solving problems-

[0011] The present invention is constituted by the following structure.

[0012] (1) A method for controlling the shape of a weld bead when manufacturing a laminated object by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feed period and a reverse feed period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at a tip of a welding torch during the one cycle,

[0013] The method for controlling the weld bead shape comprises:

[0014] The average feed speed of the welding wire is kept constant,

[0015] At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

[0016] (2) A power control method,

[0017] Based on the weld bead shape control method described in (1), the welding power source is controlled.

[0018] (3) A layered modeling method,

[0019] The weld beads formed by the weld bead shape control method described in (1) are stacked to produce a stacked shaped object.

[0020] (4) A control device,

[0021] Based on the method for controlling the weld bead shape described in (1), the welding current is controlled.

[0022] (5) A welding power source,

[0023] A control device as described in (4) is provided.

[0024] (6) A welding system,

[0025] A welding power source as described in (5) is provided.

[0026] (7) A cascading modeling system,

[0027] The welding system according to (6) is provided, wherein the weld beads are stacked to shape a stacked shape object.

[0028] (8) A program for realizing a function of controlling the shape of a weld bead when a laminated object is manufactured by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feed period and a reverse feed period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at the tip of a welding torch during the one cycle,

[0029] The program enables the computer to implement the following functions:

[0030] The average feed speed of the welding wire is kept constant,

[0031] At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

[0032] -Effects of the Invention-

[0033] According to the present invention, even when welding is performed by repeatedly feeding and retracting the welding wire, the shape of the weld bead can be kept constant in real time without changing the average feeding speed of the welding wire and independently of the distance between the welding tip and the base material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram showing the overall structure of the cascade molding system.

[0035] Figure 2 : is a block diagram showing a schematic configuration of a power supply control unit in a welding power supply unit.

[0036] Figure 3 This is a timing chart of the welding current, wire feed speed, and welding voltage controlled by the power supply control unit.

[0037] Figure 4 Graphs showing waveforms of welding current and welding voltage in the first control example.

[0038] Figure 5 : is a flowchart showing the procedure of adjusting the peak current according to the short circuit time and the welding voltage.

[0039] Figure 6 Graphs showing waveforms of welding current and welding voltage in the second control example.

[0040] Figure 7 This is a flowchart showing a procedure for setting a peak current according to the presence or absence of a short circuit.

[0041] Figure 8 Graphs showing waveforms of welding current, welding voltage, and wire feed speed in the third control example.

[0042] Fig. 9 This is a flowchart showing the procedure for controlling the welding current and the wire feed speed according to the presence or absence of a short circuit. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0044] <Structure of welding equipment>

[0045] Here, a welding system used in the molding of a stacked molded body is described. The welding system shown here is used in the case of manufacturing a stacked molded object of a three-dimensional shape by stacking weld beads, and the forward feeding period and the reverse feeding period of the welding wire are periodically repeated as one cycle, and an arc period and a short circuit period are set during the one cycle to form a weld bead when an arc is generated at the front end of the welding torch. The welding system controls the shape of the weld bead when such weld beads are repeatedly stacked to manufacture a stacked molded object. The structure of the welding system described below is an example and is not limited to this.

[0046] Figure 1 1 is a schematic diagram showing the overall structure of the stacking modeling system 100 .

[0047] The stacking molding system 100 as an example of a welding system includes a robot 11 , a robot control unit 13 , a welding wire supply unit 15 , a welding power source unit 17 , and a control device 19 .

[0048] The manipulator 11 is, for example, a multi-jointed robot, and supports a welding wire M in a continuously supplyable manner in a welding torch 21 provided on a front end axis. The welding torch 21 holds the welding wire M in a state of protruding from the front end. The position and posture of the welding torch 21 can be arbitrarily set three-dimensionally within the range of the degrees of freedom of the robot arm constituting the manipulator 11. The manipulator 11 preferably has more than six axes of freedom, and preferably can arbitrarily change the position of the heat source at the front end of the welding torch along the axial direction of the welding torch. In addition to Figure 1 In addition to the multi-joint robot having four or more axes shown, various forms such as a robot having angle adjustment mechanisms on two or more orthogonal axes may be possible.

[0049] The welding torch 21 has a shielding nozzle not shown in the figure, and a shielding gas is supplied from the shielding nozzle. The shielding gas blocks the atmosphere and prevents oxidation and nitridation of the molten metal during welding, thereby suppressing poor welding. The arc welding method used in this structure may be any of a consumable electrode type such as coated arc welding or carbon dioxide arc welding, a non-consumable electrode type such as TIG (Tungsten Inert Gas: tungsten inert gas shielded welding) welding or plasma arc welding, and is appropriately selected according to the stacked body to be shaped. Here, the metal arc welding is used as an example for explanation. In the case of the consumable electrode type, a conductive nozzle is arranged inside the shielding nozzle, and the welding wire M that supplies current is held on the conductive nozzle. The welding torch 21 holds the welding wire M, and at the same time generates an arc from the front end of the welding wire M in the shielding gas atmosphere.

[0050] The robot control unit 13 mainly controls the movement of the robot 11. The robot control unit 13 holds training data that predetermines the movement mode, welding start position, welding end position, welding conditions, swinging movement, etc. of the robot 11, and controls the movement of the robot 11 by indicating these training data to the robot 11. In addition, the robot control unit 13 gives information on welding conditions such as welding current, welding voltage, and feed speed in welding work to the welding power supply unit 17 according to the training data. The robot control unit 13 is connected to a controller (not shown) and can instruct an operator to perform any operation on the robot control unit 13 via the controller.

[0051] The welding wire supply unit 15 supplies the welding wire M to the welding torch 21. The welding wire supply unit 15 includes a reel 15a on which the welding wire M is wound, and a drawing mechanism 15b that draws out the welding wire M from the reel 15a. The drawing mechanism 15b includes a feed motor or the like that serves as a power for drawing out the welding wire M. The welding wire M is fed to the welding torch 21 while being sent out in the forward direction or the reverse direction as required by the drawing mechanism 15b. That is, at the front end of the welding torch 21, the position of the front end of the welding wire M is changed by feeding the welding wire M in the forward direction or the reverse direction. The drawing mechanism 15b is not limited to a push type that is arranged on the side of the welding wire supply unit 15 and pushes out the welding wire M, but may be a pull type or a push-pull type that is arranged on a robot arm or the like.

[0052] The welding power supply unit 17 includes a power supply and a power supply control unit for supplying power required for welding performed by the robot 11. The welding power supply unit 17 adjusts the welding current and welding voltage supplied when the welding wire M is melted and solidified to form a weld bead. In addition, the feeding speed of the welding wire M by the welding wire supply unit 15 is adjusted in conjunction with the welding conditions such as the welding current and welding voltage set by the welding power supply unit 17.

[0053] The heat source for melting the welding wire M is not limited to the above-mentioned electric arc. For example, a heating method using an electric arc and a laser, a heating method using plasma, a heating method using an electron beam or a laser, and other heat sources based on other methods may also be used. In the case of heating by an electron beam or a laser, the amount of heating can be more finely controlled, and the state of the formed weld bead can be more appropriately maintained, which helps to further improve the quality of the laminated structure. In addition, the material of the welding wire M is not particularly limited, for example, mild steel, high-tensile steel, aluminum, aluminum alloy, nickel, nickel-based alloy, etc., and the type of welding wire M used may be different depending on the characteristics of the laminated structure.

[0054] The stacked molding system 100 of the above structure operates according to a molding program created based on a molding plan for a stacked molding body. The molding program is composed of a plurality of command codes and is created based on an appropriate algorithm according to various conditions such as the shape, material, and heat input of the molding object. When the welding torch 21 is moved according to the molding program and the fed welding wire M is melted and solidified at the same time, a linear weld bead B as a molten solidified body of the welding wire M is formed on the base 23. That is, the robot control unit 13 drives each unit such as the robot 11, the welding wire supply unit 15, and the welding power supply unit 17 based on a given molding program provided from the control device 19. The robot 11 melts the welding wire M with an arc while moving the welding torch 21 according to the instruction from the robot control unit 13 to form the weld bead B. In this way, by sequentially forming and stacking the weld bead B, a stacked molding body (workpiece W) of a target shape can be obtained.

[0055] <Functional structure of welding power supply unit>

[0056] Next, the functional structure of welding power supply unit 17 will be described in detail.

[0057] Figure 2 1 is a block diagram showing a schematic configuration of a power supply control unit in welding power supply unit 17 .

[0058] The power supply control unit of the welding power supply unit 17 is implemented by, for example, the control device 19 or a computer (not shown) executing a program.

[0059] The power supply control unit of the welding power supply unit 17 includes a current setting unit 31. The current setting unit 31 in the present embodiment has a function of setting various current values ​​for regulating the welding current flowing through the welding wire M. The current setting unit 31 also has the following functions: a function of setting the start time t1 and the end time t2 of the period for suppressing the current value of the welding current by a current suppression period setting unit 31a; a function of detecting the short circuit time by a short circuit time detection unit 31b; and a function of setting the target value of the peak current by a peak current target value setting unit 31c.

[0060] Figure 3 This is a timing chart of the welding current, wire feed speed, and welding voltage controlled by the power supply control unit.

[0061] In the case of the present embodiment, the welding current represents a pulse waveform of the welding current that alternately repeats the current non-suppression period and the current suppression period. The current setting unit 31 sets the set current value I during the current non-suppression period. p (Hereafter, also referred to as "peak current I p ”.) and the set current value I during current suppression b (Hereafter, also referred to as "base current I b ".). Peak current I p From the base current I b The rising waveform is used to set the base current I b The current setting unit 31 basically sets the peak current I based on the information of the wire tip position (wire feed speed signal). p And the base current I b These two values ​​are used to control the welding current.

[0062] Figure 2 The power supply main circuit of the welding power supply unit 17 shown includes a three-phase AC power supply (hereinafter also referred to as “AC power supply”) MC1, a primary-side rectifier MC2, a smoothing capacitor MC3, a switching element MC4, a transformer MC5, a secondary-side rectifier MC6, and a reactor MC7.

[0063] The AC power input from the AC power supply MC1 is full-wave rectified by the primary-side rectifier MC2, and then smoothed by the smoothing capacitor MC3, and converted into DC power. Next, the DC power is converted into high-frequency AC power by inverter control based on the switching element MC4, and then converted into secondary-side power via the transformer MC5. The AC output of the transformer MC5 is full-wave rectified by the secondary-side rectifier MC6, and then smoothed by the reactor MC7. The output current of the reactor MC7 is given to the welding tip of the welding torch 21 as the output from the power supply main circuit, and energizes the welding wire M as a consumable electrode.

[0064] The welding wire M is fed by the feed motor of the extraction mechanism 15b, and an arc 33 is generated between the welding wire M and the workpiece (also referred to as the base material) W. In the case of the present embodiment, the extraction mechanism 15b is provided with a forward feed period TP ( Figure 2 ), and a reverse feed period TN ( Figure 2). And, when the forward feed period TP and the reverse feed period TN are set as one cycle, the extraction mechanism 15b feeds the welding wire M in a periodically switched manner. Hereinafter, the movement of the front end of the welding wire M toward the base material W is also referred to as "forward feed" or "delivery", and the reverse direction is referred to as "reverse feed" or "retraction". In addition, the "front end of the welding wire" mentioned here generally refers to the front end of the welding wire when the existence of the molten droplet hanging from the front end of the welding wire M is ignored. That is, it is considered that the welding wire M melted by the arc 33 is immediately transferred to the base material W.

[0065] Feeding of welding wire M by drawing mechanism 15b is controlled by control signal Fc from feed drive unit 35. The average value of the feeding speed of welding wire M (average feeding speed) is substantially the same as the melting speed of welding wire M and is kept constant in the present embodiment.

[0066] The current setting unit 31 is supplied with a voltage setting signal V from the voltage setting unit 37. r , the voltage setting signal V r is the target value of the voltage applied between the welding tip of the welding torch 21 and the base material W. Here, the voltage setting signal V r is also given to the voltage comparison unit 39 and is compared with the voltage detection signal V detected by the voltage detection unit 41. o In addition, the voltage detection signal V o The voltage comparison unit 39 converts the voltage setting signal V r With the voltage detection signal V o The difference is amplified as the voltage error amplification signal V a Output to the current setting unit 31.

[0067] The current setting unit 31 sets the voltage based on the voltage setting signal V r and voltage error amplified signal V a , reset the peak current I p The value of the base current I b The value of the peak current I p During the period, or the peak current I p The value of the base current I b The value of the reset period or value is set to the current target value I r The current setting signal is output to the current error amplifier 43.

[0068] The current error amplifier 43 takes the current target value I r The current setting signal given and the current detection signal I detected by the current detection unit 45 o The difference is amplified as the current error amplification signal E dThe inverter driving unit 47 outputs the current error signal E to the inverter driving unit 47. The inverter driving unit 47 amplifies the current error signal E according to the current error signal E. d To correct the drive signal E of the switching element MC4 c .

[0069] The current setting unit 31 also receives a short-circuit detection signal D which is a signal that a short circuit of the welding current is detected. rl . Short circuit detection signal D rl The short-circuit detection unit 49 outputs the voltage detection signal V output by the voltage detection unit 41. o The changes in the welding current are monitored and a short circuit of the welding current is sensed based on the changes.

[0070] The short-circuit detection unit 49 here, for example, detects the voltage signal V o The value of is compared with a detection threshold value to detect a short circuit. The detection threshold value is pre-stored in a storage unit (not shown).

[0071] The current setting unit 31 is also given an average feed speed F of the welding wire M to be fed. ave . Average feed speed F ave The average feed speed setting unit 51 outputs the average feed speed F based on training data stored in a storage unit (not shown). The current setting unit 31 outputs the average feed speed F based on the average feed speed F given to it. ave , to determine the peak current I p , Base current I b The current values ​​of each p At the moment t1 when power is turned on, the base current I b Various parameters such as the time t2 when energization ends.

[0072] Average feed speed F ave The amplitude feed speed setting unit 53 sets the average feed speed F based on the input average feed speed F. ave , to determine the amplitude W f The so-called amplitude feed refers to the feed speed being higher than the average feed speed F. ave The forward feed period of the large period and the feed speed relative to the average feed speed F ave The feed speed is relative to the average feed speed F. ave The small period refers to the period less than the average feed speed F ave , including negative feed speed, i.e., the speed at which the tip of the welding wire moves in the direction opposite to the position of the base material W. Amplitude W f Given relative to the average feed speed F aveThe amplitude change range is given by the period Tf as the time of the amplitude change as a repetition unit. The amplitude feed speed setting unit 53 generates the amplitude W which is determined f Amplitude feed speed F corresponding to the period Tf or frequency f f and output to the feed speed setting unit 55.

[0073] The feed speed setting unit 55 sets the feed speed F based on the amplitude. f and average feed speed F ave , output feed speed target value signal F r In the present embodiment, the feed speed target value signal F r It is expressed by the following formula.

[0074] [Mathematical formula 1]

[0075]

[0076] Feed speed target value signal F r The signal is output to the phase shift detection unit 57 , the feed error amplification unit 59 , and the current setting unit 31 .

[0077] The feed error amplifier 59 converts the feed speed target value signal F as information on the target speed into r , and a feed speed detection signal F obtained by measuring the feed speed of the welding wire M by the extraction mechanism 15b. o The difference is amplified and the speed error signal F with the corrected error value is amplified. d The signal is output to the feed drive unit 35 .

[0078] The feed drive unit 35 amplifies the speed error signal F d Generate control signal F c , the control signal F c The feed speed converter 61 converts the rotation amount of the drive motor of the feed mechanism 15b into a feed speed detection signal F of the welding wire M. o .

[0079] The phase shift detection unit 57 of this embodiment converts the feed speed target value signal F r and the feed speed detection signal F as the measured value o For comparison, the output phase shift time T θd The phase shift detection unit 57 may also measure the feeding action of the extraction mechanism 15b when a parameter defining the amplitude feeding is made variable, such as the period Tf, the amplitude W, etc. f etc., and find the phase shift time T θd .

[0080] Phase shift time T θd The current setting unit 31 is given the feed speed target value signal F. r and phase shift time T θd , and correct the error in the feed amount of the welding wire M. The above are the basic functions of the power supply control unit.

[0081] <Welding current control>

[0082] Next, control of the welding current using the above-mentioned power supply control unit will be described.

[0083] like Figure 3 As shown, in this embodiment, the average feed speed F ave The welding wire is fed to the front end of the welding torch at a sinusoidal feeding / retracting speed, and the welding current is changed according to the feeding action of the welding wire. Here, the arc length, which is an important factor in reducing the heat input, can be controlled by the retraction amount of the welding wire M and the output peak current I p This control is performed based on speed control rather than position control of the welding wire M. The feeding speed of the welding wire is integrated over time to obtain the feeding amount and the retracting amount of the welding wire M.

[0084] In the basic control example shown here, when the welding wire M starts to be fed from the uppermost position P1 of the feed amplitude, the welding current is increased, and the welding current is reduced at the maximum speed reaching point (wire middle point P2) to deal with short circuit. In addition, a short circuit occurs when the welding wire approaches the lowest point P3, and preferably, after the welding wire passes the lowest point P3 and turns to the withdrawal of the welding wire, the short circuit is released and the arc is re-ignited. The timing of increasing the welding current is determined by the command value of the welding wire feeding speed, and the maximum speed reaching point is determined by the detected value of the welding wire feeding speed, but it is not limited to this. The measurement of the welding wire feeding speed can be implemented by using a known means such as an encoder that detects the rotation of the motor of the withdrawal mechanism 15b.

[0085] In this process, the welding wire M will be fed at an average speed F ave The welding current is set to be constant and operates at the set forward and reverse frequency and amplitude of the wire feed. Therefore, the peak value of the welding current becomes the control operation amount. Specifically, the average value of the welding voltage and the short-circuit time during the arc are fed back, and the peak current I is controlled (for example, PI control) using the deviation from their target values. p , so that the arc length is within a given range. By using this control method, welding with a wire feed speed of about 3 mpm or more can be stably performed. However, when the feed speed is lower than 3 mpm, it is difficult to maintain the melting balance of the wire, and a non-short circuit state or a short circuit state often lasts for a long time, making it difficult to form a stable weld bead.

[0086] For this reason, in the present control method, a specific process is added so that the prescribed short circuit period can be obtained reliably. When the short circuit period is inappropriate, a short circuit is generated or forced to be generated within a necessary and sufficient period, so that a stable weld bead shape can be formed even if the wire feed speed is 1 mpm. In addition, in each control example described below, as a premise, the average feed speed (value per unit time or per unit cycle) of the wire feed speed is set to be constant. Therefore, according to the present control method, since the weld bead shape is stable, a stacked molded object with high shape accuracy can be manufactured in real time and stably.

[0087] <First control example>

[0088] Figure 4 Graphs showing waveforms of welding current and welding voltage in the first control example.

[0089] In the first control example, the length of the short circuit period (short circuit time) is measured, and the obtained short circuit time is compared with the predetermined short circuit target time. When the short circuit time is much longer or much shorter than the short circuit target time, the welding current is adjusted so that the short circuit time becomes the short circuit target time. The short circuit target time may not be a single point, but may be set to a specific time range. When a specific time range is set, the welding current is adjusted so that the short circuit time converges within the specific time range. In this control example, the average feed speed F of the welding wire is set to 0. ave Set to 1.5 mpm.

[0090] like Figure 3 As shown, when the peak current I is set during the forward feeding period TP of the welding wire, p The welding current is reduced to the base current I b When the front end of the welding wire being fed forward is short-circuited with the base material, the welding voltage drops sharply. Furthermore, when the front end of the welding wire separates from the base material during the reverse feeding period TN of the welding wire and enters the arc period, the welding voltage increases again. The period of decrease in the welding voltage corresponds to the short-circuit period St. The short-circuit period St can be determined based on the waveform of the welding voltage.

[0091] Specifically, Figure 2 The voltage detection unit 41 shown in FIG. 4 is used to detect the voltage waveform of the welding voltage (voltage detection signal V o ) is detected, and the short circuit detection unit 49 is based on Figure 4 The welding voltage detection signal V o To detect the short circuit period St, and the short circuit detection signal D rl The short-circuit detection unit 49 outputs the voltage detection signal V o The voltage value and the predetermined short-circuit judgment voltage Vth Compare the voltage detection signal V o Exceeding the short circuit judgment voltage V th (V o >V th ) is judged as the arc period, and the voltage signal is th Below (V o ≤V th ) is determined as a short-circuit period. Thus, the short-circuit period can be accurately detected.

[0092] The short-circuit detection unit 49 uses the determination result as a short-circuit detection signal D rl The short circuit detection signal D is output to the current setting unit 31. The short circuit time detection unit 31b of the current setting unit 31 detects the short circuit time based on the input short circuit detection signal D. rl and voltage detection signal V o , to detect the time length of the short-circuit period St, that is, the short-circuit time Δt(i) (i is an integer), and output the short-circuit time Δt(i) to the peak current target value setting unit 31 c.

[0093] The peak current target value setting unit 31 c adjusts the next period Tf ( ) by the correction value ΔI according to the obtained short-circuit time Δt(i), as shown in the formula (2). Figure 3 ) during the forward feed period of TP p Current target value I of (i+1) r (i+1).

[0094] [Mathematical formula 2]

[0095]

[0096] For example, when it is determined that the short-circuit time Δt(1) is shorter than the short-circuit target time range, the peak current I p (1) Add a negative correction value ΔI to correct the peak current I of the next cycle p (2) Current target value I r (2). In the next short-circuit period St, the short-circuit time Δt(2) is also detected. If it is determined that the short-circuit time Δt(2) is longer than the short-circuit target time range, the peak current I p (2) adds a positive correction value ΔI to correct the peak current Ip of the next cycle (3) to the current target value I r (3) Each correction value ΔI is set according to the length of the short-circuit time. In this way, for each short-circuit period St, the peak current I in the next cycle Tf is adjusted according to each short-circuit time Δt(i). p (i+1), so that the short-circuit period St always converges within the short-circuit target time range.

[0097] The correction value ΔI is set based on characteristic information that associates the peak current value with the short-circuit time. The characteristic information may be a predetermined calculation formula or a table value obtained experimentally or analytically and stored as a database in a storage unit (not shown).

[0098] The peak current target value setting unit 31c may also set the peak current I according to the short circuit time and the welding voltage. p target value.

[0099] Figure 5 The peak current I is adjusted according to the short circuit time and welding voltage. p In this case, the voltage target value V in each short-circuit period St is preset. ref (i) and the short-circuit time target value st_ref.

[0100] First, as shown in equation (3), the voltage target value V is calculated as the voltage error ev(i): ref (i) With the voltage detection signal V o The difference in voltage value (step S11, hereinafter referred to as S11).

[0101] [Mathematical formula 3]

[0102]

[0103] Furthermore, as shown in the equation (4), the difference between the short-circuit time target value st_ref(i) and the short-circuit time detection value st(i) is obtained as the short-circuit time error e_st(i) ( S12 ).

[0104] [Formula 4]

[0105]

[0106] Next, the current target value I of the peak current in the next cycle Tf is calculated using the obtained voltage error ev(i) and short-circuit time error e_st(i) by equation (5): r (i+1)(S13).

[0107] [Mathematical formula 5]

[0108]

[0109] Here, K vp is the voltage error gain, K stp is the time error gain.

[0110] The peak current target value I obtained by equation (5) is r(i+1) is output to the current error amplifier 43 (S14). p The current value is changed to the current target value I r As a result, the short-circuit time is set more appropriately, and the effect of maintaining the arc length constant can be enhanced.

[0111] As described above, in this control, the average feed speed of the welding wire is kept constant during the weld bead stacking, and based on the relationship between the peak current value of the welding current and the short-circuit time, the short-circuit time is detected for each cycle of the welding wire feed and the control of adding the adjustment amount to the peak current value is performed so that the short-circuit time converges within the target range. Such welding current adjustment is implemented by real-time feedback (FB) control. Therefore, by performing FB control in real time for each pulse in the current waveform (or each cycle Tf of the forward and reverse feed of the welding wire), the melting cycle of the welding wire can be stabilized even under low heat input conditions such as the feeding speed of the welding wire being 1 mpm to 3 mpm.

[0112] <Second control example>

[0113] In the cycle of melting, welding, and separation of the welding wire, sometimes even if the front end of the welding wire is fed to the bottom of the amplitude feed, there will be no short circuit. This is because the feeding amount of the welding wire is reduced due to external force, etc., which causes the distance between the welding tip and the base material to be longer than expected. Therefore, in this control, according to the cycle of forward feeding and reverse feeding of the welding wire, whether it is a short circuit or not is detected. If no short circuit occurs during the reverse feeding period TN, the welding current is suppressed so that the welding current in the next period Tf does not reach the peak current I p As a result, no droplets of the welding wire are formed, and the generation of sputtering is suppressed. p The suppression of is performed as real-time FB control at each cycle Tf of the feeding of the welding wire.

[0114] Figure 6 Graphs showing waveforms of welding current and welding voltage in the second control example. Figure 7 It shows that the peak current I is set according to whether there is a short circuit. p Flowchart of the sequence.

[0115] In the second control example, Figure 2 The short circuit detection unit 49 shown in FIG. o The presence or absence of a short circuit is detected at each cycle Tf of the feeding of the welding wire. The presence or absence of a short circuit is detected based on the waveform of the welding voltage (voltage detection signal V o ) is judged and the result is used as the short-circuit detection signal D rlThe short-circuit detection signal D is output to the current setting unit 31 (S21). rl When there is a short circuit (St(i)>0), the current setting unit 31 sets the welding current to have a peak current I in the next cycle Tf. p The current target value I r ( S22 ). On the other hand, if there is no short circuit, it is set that the peak current I p While maintaining the base current I b The current target value I r (S23).

[0116] According to this control example, when a short circuit does not occur in one cycle Tf, in the cycle Tf next to the cycle Tf, no peak current I is generated during the forward feeding period TP of the welding wire. p , and temporarily suppress the peak current I p The addition of the base current I b Thus, it is possible to prevent the scattering of the molten droplet at the tip of the welding wire that would otherwise occur if the peak current were generated in the next cycle Tf. As a result, it is possible to suppress the generation of sputtering and the change in the shape of the weld bead. In addition, in this control example, as in the first control example, it is preferred to adjust the peak current I of the next cycle Tf according to the short circuit time. p .

[0117] <Third control example>

[0118] Figure 8 Graphs showing waveforms of welding current, welding voltage, and wire feed speed in the third control example. Fig. 9 This is a flowchart showing the procedure for controlling the welding current and the wire feed speed according to the presence or absence of a short circuit.

[0119] As described above, in the cycle of melting, welding, and separation of the welding wire, sometimes even if the front end of the welding wire is sent to the bottom end of the amplitude feed, there is no short circuit, and the distance between the welding tip and the base material is longer than expected. For this reason, in this control, if no short circuit occurs within the cycle Tf of the forward and reverse feed of the welding wire, the welding wire is not fed in the reverse direction, and the welding wire is continuously fed in the forward direction until a short circuit occurs. In this way, the front end of the welding wire is brought close to the base material, and a short circuit is forced to occur. This promotes the continuous formation of the weld bead.

[0120] Figure 8 The time ta0 in the waveform of the welding voltage shown in FIG. 1 represents the average feed speed F immediately before the tip of the welding wire reaches the lowest end of the amplitude feed. ave However, when the average feed speed F is reached during the transition from the forward feed period TP to the reverse feed period TN of the next cycle Tf, aveAt the time ta, the welding voltage remains in a non-short-circuited state. In this case, in this control, the welding wire is not retracted and the average feed speed F is maintained. ave The welding wire is continuously fed forward and the welding wire is started to be withdrawn at time tb when a short circuit occurs.

[0121] Specifically, similarly to the second control example, Figure 2 The short circuit detection unit 49 shown in FIG. o The presence or absence of a short circuit is detected at each cycle Tf of the feeding of the welding wire (S31). The presence or absence of a short circuit here is detected by the waveform of the welding voltage (voltage detection signal V o ) and short circuit detection voltage V th to judge by comparison.

[0122] In addition, the current setting unit 31 detects that the average feed speed F is reached when the forward feed period TP is shifted to the reverse feed period TN. ave If a short circuit occurs at the time ta when the current setting unit 31 detects that a short circuit occurs, the cycle returns to normal and the welding current of the next cycle Tf is set to the peak current I p (S32) On the other hand, if a short circuit does not occur, the welding current of the current cycle Tf is maintained at the base current I b unchanged (S33), the feed speed setting unit 55 stops the amplitude feed (F f = 0), the output makes the welding wire feed at the average speed F ave Then, the feed speed setting unit 55 outputs a control signal to set the average feed speed F ave Set the feed speed target value signal F as the target speed r (F r =F ave ), the feeding speed of the welding wire M by the extraction mechanism 15b is set to the average feeding speed F ave .

[0123] Furthermore, the welding wire M is fed at an average feed speed F ave Continue forward feeding (period T fd ). When the short-circuit detection unit 49 detects a short circuit in this state (S35), the current setting unit 31 restarts the amplitude feeding and outputs a feed speed target value signal F to cause the feed speed setting unit 55 to start reverse feeding. r (S36) Thus, the process returns to the normal cycle, and in S32 the welding current of the next cycle Tf is set to the peak current I p .

[0124] From the viewpoint of making the welding speed constant, during the feeding period T from the above-mentioned time ta to the time tb, the welding wire is fed forward. fd Set the feed speed to the preset average feed speed F ave Therefore, the average feed speed F of the whole process is ave It does not fluctuate and is easy to maintain the shape of the weld bead constant.

[0125] The feeding speed of the welding wire can also be controlled by switching the torque value generated by the feeding motor of the extraction mechanism 15b. In addition, in this control example, as in the first control example, it is preferred to adjust the peak current I of the next cycle Tf according to the short circuit time. p .

[0126] Thus, the present invention is not limited to the above-mentioned embodiments, and the combination of the structures of the embodiments and the changes and applications made by those skilled in the art based on the description in the specification and known technologies are also the intended contents of the present invention and are included in the scope of protection required.

[0127] The above-mentioned control examples are mainly implemented by the power supply control unit of the welding power supply unit 17, but the control examples may be implemented by the control device 19 or by another computer via a network or the like. In addition, the welding power supply unit 17 may be configured as a welding power supply including the control device 19.

[0128] As described above, the following matters are disclosed in this specification.

[0129] (1) A method for controlling the shape of a weld bead when manufacturing a laminated object by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feed period and a reverse feed period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at a tip of a welding torch during the one cycle,

[0130] The method for controlling the weld bead shape comprises:

[0131] The average feed speed of the welding wire is kept constant,

[0132] At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

[0133] According to this method of controlling the weld bead shape, a weld bead can be stably formed in real time by setting a short circuit period of an appropriate time.

[0134] (2) In the method for controlling the weld bead shape described in (1),

[0135] Regarding the adjustment of the peak current value, when the short-circuit time is smaller than the target range, the peak current value is reduced, and when the short-circuit time is larger than the target range, the peak current value is increased.

[0136] According to this method of controlling the weld bead shape, the cycle of melting, welding, and separation of the welding wire can be stabilized by precisely adjusting the short circuit time.

[0137] (3) In the method for controlling the weld bead shape described in (1) or (2),

[0138] The short circuit time is a period during which the welding voltage is equal to or lower than a predetermined short circuit determination voltage.

[0139] According to this method of controlling the weld bead shape, the short circuit period can be accurately detected based on the short circuit determination voltage.

[0140] (4) In the method for controlling the weld bead shape described in (3),

[0141] The method for controlling the weld bead shape comprises:

[0142] The average value of the welding voltage during the period of conducting the welding with the peak current value is obtained.

[0143] The target value of the peak current value is determined based on the short-circuit time and the average value of the welding voltage.

[0144] According to this method of controlling the weld bead shape, the short-circuit time can be adjusted more appropriately.

[0145] (5) In the method for controlling a weld bead shape according to any one of (1) to (4),

[0146] In one cycle of feeding the welding wire, when there is no transition from the arc period to the short circuit period, conduction at the peak current value is temporarily suppressed.

[0147] According to this method of controlling the shape of a weld bead, it is possible to prevent the scattering of droplets at the tip of the welding wire, and to suppress the occurrence of spatter and the change in the shape of the weld bead.

[0148] (6) In the method for controlling the weld bead shape described in (5),

[0149] After energization is performed at the peak current value during the forward feed period of the one cycle, if there is no transition from the arc period to the short circuit period within the one cycle, in the next cycle following the one cycle, energization at the peak current value is not performed, and a base current lower than the peak current value is continuously maintained.

[0150] According to this method of controlling the weld bead shape, it is possible to prevent the scattering of the molten droplet at the tip of the welding wire that occurs when the peak current is generated in the next cycle Tf, and to suppress the occurrence of spatter and the change in the shape of the weld bead.

[0151] (7) In the method for controlling a weld bead shape described in any one of (1) to (4),

[0152] When the welding wire feed speed decreases and reaches the average feed speed without transitioning from the arc period to the short circuit period, the welding wire is fed out while the welding wire feed speed is maintained at the average feed speed until transitioning to the short circuit period.

[0153] According to this method of controlling the shape of a weld bead, the tip of the welding wire is brought close to the base material to forcibly generate a short circuit, thereby promoting the continuous formation of the weld bead.

[0154] (8) A power supply control method,

[0155] The welding power source is controlled based on the method for controlling a weld bead shape described in any one of (1) to (7).

[0156] According to this power supply control method, the shape of the weld bead is stabilized by power supply control, and good welding can be performed.

[0157] (9) A layered modeling method,

[0158] The weld beads formed by the weld bead shape control method described in any one of (1) to (7) are stacked to produce a stacked shaped object.

[0159] According to this stacking modeling method, since the weld bead shape is stable, a stacking modeled object having a stacked shape with higher accuracy can be manufactured.

[0160] (10) A control device,

[0161] The welding current is controlled based on the weld bead shape control method described in any one of (1) to (7).

[0162] According to this control device, a weld bead can be stably formed by controlling the welding current.

[0163] (11) A welding power source,

[0164] A control device as described in (10) is provided.

[0165] According to this welding power source, various parts can be controlled by adjusting the short-circuit period by the welding power source itself, thereby easily forming a good weld bead with high shape accuracy.

[0166] (12) A welding system,

[0167] A welding power source as described in (11) is provided.

[0168] According to this welding system, welding with high shape accuracy can be performed.

[0169] (13) A layered modeling system,

[0170] The welding system according to (12) is provided, wherein the weld beads are stacked to shape a stacked shape object.

[0171] According to this stacking molding system, a stacking molded object with high shape accuracy can be manufactured.

[0172] (14) A program for realizing a function of controlling the shape of a weld bead when a laminated object is manufactured by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feed period and a reverse feed period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at the tip of a welding torch during the one cycle,

[0173] The program enables the computer to implement the following functions:

[0174] The average feed speed of the welding wire is kept constant,

[0175] At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

[0176] According to this program, a weld bead can be stably formed in real time by setting a short circuit period of an appropriate time.

[0177] In addition, the present application is based on the Japanese patent application (Japanese Patent Application No. 2022-080525) filed on May 16, 2022, the contents of which are incorporated herein by reference.

[0178] -Explanation of symbols-

[0179] 11. Robot

[0180] 13 Robot control unit

[0181] 15. Wire supply unit

[0182] 15a Reel

[0183] 15b Extraction mechanism

[0184] 17 Welding power supply

[0185] 19 Control Device

[0186] 21 Welding torch

[0187] 23 Base

[0188] 31 Current setting unit

[0189] 31a Current suppression period setting unit

[0190] 31b Short circuit time detection unit

[0191] 31c Peak current target value setting unit

[0192] 33 Arc

[0193] 35 Feed drive unit

[0194] 37 Voltage setting unit

[0195] 39 Voltage comparison unit

[0196] 41 Voltage detection unit

[0197] 43 Current error amplifier

[0198] 45 Current detection unit

[0199] 47 Inverter drive unit

[0200] 49 Short circuit detection unit

[0201] 51 Average feed speed setting unit

[0202] 53 Amplitude feed speed setting unit

[0203] 55 Feed speed setting unit

[0204] 57 Phase shift detection unit

[0205] 59 Feed error amplifier

[0206] 61 Feed speed conversion unit

[0207] 100 Layer Modeling System

[0208] B weld pass

[0209] Drl Short circuit detection signal

[0210] E c Drive signal

[0211] E d Current error amplification signal

[0212] F Frequency

[0213] F ave Average feed speed

[0214] F c Control Signal

[0215] F d Speed ​​error amplification signal

[0216] F f Amplitude feed speed

[0217] F r Feed speed target value signal

[0218] F o Feed speed detection signal

[0219] I b Base current

[0220] I p Peak current

[0221] I o Current detection signal

[0222] I r Current setting signal

[0223] M welding wire

[0224] MC1 three-phase AC power supply (AC power supply)

[0225] MC2 Primary Side Rectifier

[0226] MC3 smoothing capacitor

[0227] MC4 Switching Element

[0228] MC5 Transformer

[0229] MC6 Secondary Side Rectifier

[0230] MC7 Reactor

[0231] P1 Top position

[0232] P2 Wire midpoint

[0233] P3 Welding wire lowest point

[0234] TP forward feed period

[0235] TN Reverse feed period

[0236] Tf period

[0237] T θd Phase shift time

[0238] T fd During feeding

[0239] V a Voltage error amplification signal

[0240] V o Voltage detection signal

[0241] V r Voltage setting signal

[0242] W Workpiece (Laminated molding body)

[0243] W f amplitude

[0244] ΔI correction value.

Claims

1. A method for controlling the shape of a weld bead when manufacturing a laminated object by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feeding period and a reverse feeding period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at the front end of a welding torch during the one cycle, The method for controlling the weld bead shape is characterized in that: include: The average feed speed of the welding wire is kept constant, At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

2. The method for controlling the weld bead shape according to claim 1, in, Regarding the adjustment of the peak current value, when the short-circuit time is smaller than the target range, the peak current value is reduced, and when the short-circuit time is larger than the target range, the peak current value is increased.

3. The method for controlling the weld bead shape according to claim 1, in, The short circuit time is a period during which the welding voltage is equal to or lower than a predetermined short circuit determination voltage.

4. The method for controlling the weld bead shape according to claim 3, in, The method for controlling the weld bead shape comprises: The average value of the welding voltage during the period of conducting the welding with the peak current value is obtained. The target value of the peak current value is determined based on the short-circuit time and the average value of the welding voltage.

5. The method for controlling the weld bead shape according to claim 1, in, In one cycle of feeding the welding wire, when there is no transition from the arc period to the short circuit period, conduction at the peak current value is temporarily suppressed.

6. The method for controlling the weld bead shape according to claim 5, in, After power is supplied at the peak current value during the forward feed period of the one cycle, if there is no transition from the arc period to the short circuit period within the one cycle, power is not supplied at the peak current value in the next cycle following the one cycle, and a base current lower than the peak current value is continuously maintained.

7. The method for controlling the weld bead shape according to claim 1, in, When the welding wire feed speed decreases and reaches the average feed speed without transitioning from the arc period to the short circuit period, the welding wire is fed out while maintaining the welding wire feed speed at the average feed speed until transitioning to the short circuit period.

8. A power control method, It is characterized in that The welding power source is controlled based on the method for controlling a weld bead shape according to any one of claims 1 to 7.

9. A layered modeling method, It is characterized in that The weld beads formed by the weld bead shape control method according to any one of claims 1 to 7 are stacked to produce a stacked shaped object.

10. A control device, It is characterized in that The welding current is controlled based on the welding bead shape control method according to any one of claims 1 to 7.

11. A welding power source, It is characterized in that A control device according to claim 10 is provided.

12. A welding system, It is characterized in that A welding power source according to claim 11 is provided.

13. A cascading modeling system, It is characterized in that The welding system according to claim 12 is provided, wherein the weld beads are stacked to shape a stacked shape object.

14. A program for realizing a function of controlling the shape of a weld bead when a laminated object is manufactured by repeatedly laminating weld beads, wherein the weld bead is formed by periodically repeating a forward feeding period and a reverse feeding period of a welding wire as one cycle, and providing an arc period and a short circuit period for generating an arc at the front end of a welding torch during the one cycle, It is characterized in that The program enables the computer to implement the following functions: The average feed speed of the welding wire is kept constant, At the same time, based on characteristic information that associates the peak current value of the welding current rising from the base current with the short-circuit time which is the length of the short-circuit period within the one cycle, the short-circuit time is detected and the peak current value is controlled in each cycle of the welding wire feeding, so that the short-circuit time converges within the target range determined by the characteristic information.

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