JP2012143774A - Arc welding method and arc welding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc welding method and an arc welding system, allowing formation of a uniform-width bead.SOLUTION: In this arc welding method, a droplet transfer period T1 wherein a droplet 151 is transferred from a consumable electrode 15 to a base material W while generating an arc a1 between the consumable electrode 15 and the base material W, and a cooling period T2 wherein a molten pool formed in the base material W is cooled are repeated. The arc welding method includes processes of: repeatedly passing a current of a unit pulse waveform which includes a peak period Tp passing a current of a peak value ip and a base period Tb passing a current of a base value ib smaller than the peak value ip from the consumable electrode 15 to the base material W during each droplet transfer period T1; moving the consumable electrode 15 in a welding advance direction along the base material W relatively to the base material W during each cooling period T2; and ending the droplet transfer period T1 when the frequency of the peak period Tp in each droplet transfer period T1 reaches a set frequency. Thereby, size of each welded mark formed in the base material W in each droplet transfer period T1 can be uniform. Accordingly, the uniform-width good-looking bead can be formed.

Description

  The present invention relates to an arc welding method and an arc welding system.

  Conventionally, a welding method that repeats a droplet transfer period and a cooling period is known (see, for example, Patent Document 1). In this welding method, the droplet is transferred from the consumable electrode to the base material during the droplet transfer period. During the droplet transfer period, the welding torch holding the consumable electrode is stopped with respect to the base material. Thus, a circular molten pool is formed in plan view during the droplet transfer period. On the other hand, during the cooling period, a slight welding current that does not transfer droplets from the consumable electrode to the base material is allowed to flow from the consumable electrode to the base material. Further, during the cooling period, the welding torch is moved to a point in the base material where the next droplet transfer period starts. During the cooling period, the molten pool is solidified to form welding marks. The droplet transfer period and the cooling period as described above are repeated. As a result, a scaly bead is formed in which circular welding marks are continuous in one direction.

  In the conventional welding method, the welding robot or the welding power supply device controls the length of each droplet transfer period to be a certain length. In such a method, the length of each droplet transfer period is unlikely to be a fixed length and often varies. When the length of each droplet transfer period varies, the size of the circular weld mark varies. If it does so, the width | variety of a bead will become non-uniform | heterogenous and will cause deterioration of the external appearance of a bead.

Japanese Patent Laid-Open No. 11-267839

  The present invention has been conceived under the circumstances described above, and an object thereof is to provide an arc welding method and an arc welding system capable of forming a bead having a uniform width.

  An arc welding method provided by the first aspect of the present invention includes a droplet transfer period in which a droplet is transferred from the consumable electrode to the base material while generating an arc between the consumable electrode and the base material, An arc welding method in which a cooling period for cooling a molten pool formed in a base material is repeated, and during each droplet transfer period, a peak period in which current flows at a peak value and a base value smaller than the peak value. A step of repeatedly flowing a current of a unit pulse waveform including a base period through which current flows from the consumable electrode to the base material, and the consumable electrode with respect to the base material in the welding progress direction during each cooling period. And a step of ending the droplet transfer period when the number of times of the peak period in each droplet transfer period reaches a set number.

  In a preferred embodiment of the present invention, the step of repeatedly flowing includes a step of repeatedly generating a pulse generation instruction signal during each droplet transfer period, and a unit pulse waveform every time the pulse generation instruction signal is generated. And the step of ending the droplet transfer period includes a step of measuring the number of peak periods based on the number of times the pulse generation instruction signal is generated.

  In a preferred embodiment of the present invention, the step of ending the droplet transfer period includes a step of measuring the number of times of the peak period based on a value of a current flowing between the consumable electrode and the base material. .

  In a preferred embodiment of the present invention, when the number of peak periods in each droplet transfer period exceeds a set number, the step of starting to move the consumable electrode relative to the base material along the base material. In addition.

  In a preferred embodiment of the present invention, in the step of repeatedly flowing, in the step of moving the current from the consumable electrode to the base material so that the time average value of the absolute value is the first value, The current is passed from the consumable electrode to the base material so that the time average value of the absolute value is a second value smaller than the first value, and the second value is 5 to 20A.

  In a preferred embodiment of the present invention, in the step of repeatedly flowing, in the step of moving the current from the consumable electrode to the base material so that the time average value of the absolute value is the first value, The current flows from the consumable electrode to the base material so that the time average value of the absolute value is a second value smaller than the first value, and the second value is 0A.

  The arc welding system provided by the second aspect of the present invention includes a droplet transfer period in which a pulse current is passed from a consumable electrode to a base material, and a cooling period in which the molten pool formed in the base material is cooled alternately. The waveform of the pulse current is a shape that repeats a unit pulse waveform including a peak period in which current flows at a peak value and a base period in which current flows at a base value smaller than the peak value. A welding system, comprising a set number storage unit that stores a set number, and an end determination circuit that sends an end instruction signal when the number of times of the peak period in each droplet transfer period reaches the set number, The output circuit ends the droplet transfer periods when receiving the end instruction signal.

  In a preferred embodiment of the present invention, the output circuit includes a signal generation circuit that repeatedly generates a pulse generation instruction signal during each droplet transfer period, and the unit pulse waveform every time the pulse generation instruction signal is received. The end determination circuit includes a measurement circuit that measures the number of times of the peak period based on the number of times the pulse generation instruction signal is generated.

  In a preferred embodiment of the present invention, the termination determination circuit is based on a current detection circuit that detects a current flowing between the consumable electrode and the base material, and a current value detected by the current detection circuit. And a measuring circuit for measuring the number of times of the peak period.

  In a preferred embodiment of the present invention, the robot further comprises a welding robot that holds the consumable electrode, and an operation control circuit that sends an operation control signal to the welding robot, and the operation control circuit receives the end instruction signal. Then, a signal for moving the consumable electrode relative to the base material along the base material is sent as the operation control signal.

  According to such a configuration, the size of each welding mark formed on the base material during each droplet transfer period can be made uniform. Therefore, a clean bead having a uniform width can be formed.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure which shows the structure of the arc welding system concerning 1st Embodiment of this invention. It is a figure which shows the internal structure of the arc welding system shown in FIG. FIG. 3 is a block diagram illustrating an example of a current waveform generation circuit in FIG. 2. It is a timing chart of the signal etc. in the welding method concerning a 1st embodiment of the present invention. It is a figure which shows the timing chart shown in FIG. 4 in detail. (A) is a figure which shows the states of the arc etc. during the droplet transfer period of the welding method concerning 1st Embodiment of this invention. (B) is a figure which shows the state of the arc etc. at the time of the start of the cooling period of the welding method concerning 1st Embodiment of this invention. (C) is a figure which shows the states, such as an arc at the time of the completion | finish of the cooling period of the welding method concerning 1st Embodiment of this invention. (D) is a figure which shows states, such as an arc at the time of the restart of the droplet transfer period of the welding method concerning 1st Embodiment of this invention. It is a top view which shows the shape of the bead formed by the welding method concerning 1st Embodiment of this invention. It is a figure which shows the internal structure of the arc welding system concerning 2nd Embodiment of this invention. It is a figure which shows the internal structure of the arc welding system concerning 3rd Embodiment of this invention. It is a timing chart of the signal etc. in the welding method concerning a 3rd embodiment of the present invention. It is a figure which shows the timing chart shown in FIG. 10 in detail. It is a figure which shows the internal structure of the arc welding system concerning 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an arc welding system according to the first embodiment of the present invention.

  An arc welding system A1 shown in FIG. 1 includes a welding robot 1, a robot control device 2, and a welding power source device 3. The welding robot 1 automatically performs arc welding on the base material W. The welding robot 1 includes a base member 11, a plurality of arms 12, a plurality of motors 13, a welding torch 14, a wire feeding device 16, and a coil liner 19.

  The base member 11 is fixed to an appropriate location such as a floor. Each arm 12 is connected to the base member 11 via a shaft. The welding torch 14 guides the consumable electrode 15 (welding wire) to a predetermined position near the base material W. The welding torch 14 is provided with a shield gas nozzle (not shown). The shield gas nozzle is for supplying a shield gas such as argon. The motor 13 is a moving mechanism and is rotationally driven by the robot control device 2. By this rotational drive, the movement of each arm 12 is controlled, and the welding torch 14 can move freely up and down, front and rear, and left and right.

  The motor 13 is provided with an encoder (not shown). The output of the encoder is sent to the robot control device 2. The wire feeding device 16 is provided in the upper part of the welding robot 1. The wire feeding device 16 is for feeding the consumable electrode 15 to the welding torch 14. The wire feeding device 16 includes a feeding mechanism 161 (motor WM), a wire reel (not shown), and a wire push device (not shown). Using the feeding mechanism 161 as a drive source, the wire push device feeds the consumable electrode 15 wound around the wire reel to the welding torch 14.

  One end of the coil liner 19 is connected to the wire feeder 16 and the other end is connected to the welding torch 14. The coil liner 19 has a tube shape, and a consumable electrode 15 is inserted through the coil liner 19. The coil liner 19 guides the consumable electrode 15 delivered from the wire feeder 16 to the welding torch 14. The fed consumable electrode 15 protrudes from the welding torch 14.

  FIG. 2 is a diagram showing an internal configuration of the arc welding system A1 shown in FIG.

  The robot control device 2 includes an operation control circuit 21 and a teach pendant 23. The robot control device 2 is for controlling the operation of the welding robot 1.

  The operation control circuit 21 has a microcomputer and a memory (not shown). The memory stores a work program in which various operations of the welding robot 1 are set. The operation control circuit 21 sets the robot moving speed VR. The robot moving speed VR is the speed of the welding torch 14 with respect to the base material W in the in-plane direction of the base material W. The operation control circuit 21 sends an operation control signal Ms to the welding robot 1 based on the work program, the coordinate information from the encoder, the robot moving speed VR, and the like. The welding robot 1 receives the operation control signal Ms and rotates each motor 13. By rotating the motors 13, the welding torch 14 moves to a predetermined welding start position on the base material W or moves along the in-plane direction of the base material W. The operation control circuit 21 sends a droplet transfer start signal Ss.

  The teach pendant 23 is connected to the operation control circuit 21. The teach pendant 23 is for the user of the arc welding system A1 to set parameters and the like when performing welding.

  The welding power supply device 3 includes an output circuit 31, a current value storage unit 33, an end determination circuit 34, a set number storage unit 35, and a feed control circuit 38. The welding power source device 3 is a device for supplying the welding current Iw while applying the welding voltage Vw between the consumable electrode 15 and the base material W, and is a device for feeding the consumable electrode 15. .

  The current value storage unit 33 stores the second value ir2. The set number storage unit 35 stores the set number Nb. Each value of the second value ir2 and the set number Nb is input from the teach pendant 23 and stored in each storage unit via the operation control circuit 21, for example.

  The output circuit 31 includes a power supply circuit 311, a current detection circuit 312, a current error calculation circuit EI, a current switching circuit 313, a current control circuit 314, a current waveform generation circuit 315, a signal generation circuit 316, and a voltage detection. A circuit 317, a voltage error calculation circuit EV, and a voltage control circuit 318 are included. The output circuit 31 applies the welding voltage Vw at a value designated between the consumable electrode 15 and the base material W, or allows the welding current Iw to flow at a value designated from the consumable electrode 15 to the base material W. Is.

  The power supply circuit 311 receives, for example, a commercial power supply such as three-phase 200 V, performs output control such as inverter control and thyristor phase control, and outputs a welding voltage Vw and a welding current Iw.

  The current detection circuit 312 is for detecting the value of the welding current Iw flowing between the consumable electrode 15 and the base material W. The current detection circuit 312 sends a current detection signal Id corresponding to the value of the welding current Iw. The current error calculation circuit EI is for calculating a difference ΔIw between the value of the welding current Iw that is actually flowing and the set value of the welding current. The current error calculation circuit EI receives a current detection signal Id and a current setting signal Ir described later corresponding to the set welding current value, and sends a current error signal Ei corresponding to the difference ΔIw to the power supply circuit 311. The current error calculation circuit EI may send a current error signal Ei corresponding to a value obtained by amplifying the difference ΔIw.

  The voltage detection circuit 317 is for detecting the value of the welding voltage Vw applied between the consumable electrode 15 and the base material W. The voltage detection circuit 317 sends a voltage detection signal Vd corresponding to the value of the welding voltage Vw. In the present embodiment, the voltage detection circuit 317 sends a voltage detection signal Vd corresponding to the time average value of the welding voltage Vw. The voltage control circuit 318 is for setting the value of the welding voltage Vw applied between the consumable electrode 15 and the base material W. The voltage control circuit 318 sends a voltage setting signal Vr for instructing the value of the welding voltage Vw based on a setting voltage value stored in a storage unit (not shown). The voltage error calculation circuit EV is for calculating a difference ΔVw between the value of the welding voltage Vw actually applied and the value of the set welding voltage. The voltage error calculation circuit EV receives the voltage detection signal Vd and the voltage setting signal Vr corresponding to the set welding voltage value, and sends a voltage error signal Ev corresponding to the difference ΔVw. The voltage error calculation circuit EV may send a voltage error signal Ev corresponding to a value obtained by amplifying the difference ΔVw.

  The signal generation circuit 316 is for repeatedly generating the pulse generation instruction signal Ps. In the present embodiment, the signal generation circuit 316 is a voltage frequency conversion circuit. Therefore, the signal generation circuit 316 receives the voltage error signal Ev, converts the difference ΔVw into a frequency (1 / Tf) proportional to the difference ΔVw, and changes to a high level for a short period every period Tf. Send Ps. Since the frequency (1 / Tf) is proportional to the difference ΔVw, the period Tf is not a constant value but varies somewhat.

  The current waveform generation circuit 315 is for generating a waveform of the welding current Iw in a droplet transfer period T1 described later. Specifically, the current waveform generation circuit 315 generates a unit pulse waveform (the waveform of the welding current Iw in the period Tf in FIG. 5C) every time the pulse generation instruction signal Ps is received. The current waveform generation circuit 315 sends a current setting signal Ir1 corresponding to the generated waveform current.

  FIG. 3 is a block diagram illustrating an example of the current waveform generation circuit 315. The block diagram of the current waveform generation circuit 315 shown in the figure is for generating the unit pulse waveform shown in FIG. 5C, and if the unit pulse waveform is different from that shown in FIG. 5C. The block diagram of the current waveform generation circuit 315 is also different from that in FIG.

  As shown in the figure, the current waveform generation circuit 315 includes a timer circuit TM, a switching circuit SW, current control circuits IPR and IBR, an increase period storage unit TU, a peak period storage unit TP, and a decrease period storage unit. It has TD, peak current memory | storage part IP, and base current memory | storage part IB.

  The increase period storage unit TU stores the increase period Tu, the peak period storage unit TP stores the peak period Tp, the decrease period storage unit TD stores the decrease period Td, and the peak current storage unit IP stores the peak current value ip. The base current storage unit IB stores the base current value ib.

  The timer circuit TM receives the pulse generation instruction signal Ps and sends a period signal tss. The period signal tss is at a high level for a preset period Ts (see FIG. 5C) from the time when the pulse generation instruction signal Ps changes to a high level. The current control circuit IPR receives the period signal tss and sends a current setting signal ipr. The current control circuit IPR is connected to the increase period storage unit TU, the peak period storage unit TP, the decrease period storage unit TD, and the peak current storage unit IP. The current control circuit IPR generates a current setting signal ipr for causing the welding current Iw to have a waveform in the period Ts shown in FIG. 5 from the time when the period signal tss becomes High level (ta (1) in FIG. 5). Generate. The current control circuit IBR is connected to the base current storage unit IB. The current control circuit IBR generates a current setting signal ibr for making the welding current Iw the base current value ib.

  The switching circuit SW receives the period signal tss and the current setting signals ipr and ibr and sends the current setting signal Ir1. While the period signal tss is at the High level, the switching circuit SW sends the current setting signal ipr to the current switching circuit 313 as the current setting signal Ir1. On the other hand, while the period signal tss is at the low level, the switching circuit SW sends the current setting signal ibr to the current switching circuit 313 as the current setting signal Ir1. As described above, the current waveform generation circuit 315 generates the unit pulse waveform shown in FIG. 5C and sends the current setting signal Ir1.

  The current control circuit 314 shown in FIG. 2 is for setting the value of the welding current Iw flowing between the consumable electrode 15 and the base material W in the cooling period T2 described later. The current control circuit 314 sends a current setting signal Ir2 for causing the welding current Iw to flow at the second value ir2.

  The current switching circuit 313 switches the power supply characteristic (constant voltage characteristic or constant current characteristic) of the output circuit 31. When the power supply characteristic of the output circuit 31 is a constant voltage characteristic, the output of the output circuit 31 is controlled so that the value of the welding voltage Vw becomes a set value. On the other hand, when the power supply characteristic of the output circuit 31 is a constant current characteristic, the output of the output circuit 31 is controlled so that the value of the welding current Iw becomes a set value. More specifically, it is as follows. The current switching circuit 313 receives current setting signals Ir1 and Ir2, a droplet transfer start signal Ss described later, and an end instruction signal Es described later. When the current switching circuit 313 receives the droplet transfer start signal Ss, the switch in the current switching circuit 313 is connected to the a side in FIG. In this case, the power supply characteristic of the output circuit 31 is a constant voltage characteristic. That is, the current switching circuit 313 sends the current setting signal Ir1 as the current setting signal Ir to the current error calculation circuit EI, and the welding voltage Vw becomes a value set by the voltage control circuit 318. On the other hand, when the current switching circuit 313 receives the end instruction signal Es, the switch in the current switching circuit 313 is connected to the b side in FIG. In this case, the power supply characteristic of the output circuit 31 is a constant current characteristic. That is, the current switching circuit 313 sends the current setting signal Ir2 as the current setting signal Ir to the current error circuit EI, and the welding current Iw becomes a value set by the current control circuit 314.

  The end determination circuit 34 is for determining whether or not to end the droplet transfer period T1. The end determination circuit 34 includes a measurement circuit 341 and a comparison circuit 342. The measuring circuit 341 is for measuring the number Ns of peak periods Tp in each droplet transition period T1 (that is, the number of unit pulse waveforms of the welding current Iw in each droplet transition period T1). In the present embodiment, the measurement circuit 341 measures the number Ns of peak periods Tp based on the number of times that the pulse generation instruction signal Ps has been generated. When the number Ns of peak periods Tp in each droplet transfer period T1 reaches the set number Nb stored in the set number storage unit 35, the comparison circuit 342 outputs the end instruction signal Es to the output circuit 31 (in this embodiment, current To the switching circuit 313) and the operation control circuit 21.

  The feed control circuit 38 is for controlling the speed at which the consumable electrode 15 is fed from the welding torch 14 (feed speed Fw). The feed control circuit 38 sends a feed speed control signal Fc for instructing the feed speed Fw to the feed mechanism 161.

  Next, the arc welding method using the arc welding system A1 will be described with reference to FIGS. FIG. 4 is a timing chart of signals and the like in the arc welding method using the arc welding system A1. FIG. 4A shows a change state of the robot moving speed VR, FIG. 5B shows a connection state of the switch Sw in the current switching circuit 313 (change state of power supply characteristics), and FIG. 5C shows a change state of the welding current Iw. (D) shows the changing state of the welding voltage Vw, (e) shows the changing state of the feeding speed Fw, (f) shows the changing state of the droplet transfer start signal Ss, (g) The change state of the end instruction signal Es is shown, and (h) shows the change state of the pulse generation instruction signal Ps. In FIG. 6B, a high level indicates that the switch Sw of the current switching circuit 313 is connected to the a side, and a low level indicates that the switch Sw is connected to the b side.

  In the arc welding method using the arc welding system A1, the droplet transfer period T1 and the cooling period T2 are alternately repeated. The droplet transfer period T1 is, for example, 0.1 to 0.5 seconds. The cooling period T2 is, for example, 0.1 to 0.5 seconds. FIG. 5 is a timing chart showing in detail the change state of each signal and the like in the droplet transfer period T1 of FIG.

<Droplet transfer period T1 (time ta (1) to time ta (n + 1))>
The droplet transfer period T1 is a period for transferring the droplet 151 from the consumable electrode 15 to the base material W while generating an arc a1 between the consumable electrode 15 and the base material W. At time ta (1) shown in FIGS. 4A and 5A, the operation control circuit 21 sends an operation control signal Ms for setting the robot moving speed VR to the speed v1 to the welding robot 1. Accordingly, the speed VR of the welding torch 14 holding the consumable electrode 15 with respect to the base material W is v1. In this embodiment, v1 = 0. Therefore, during the droplet transfer period T1, the welding torch 14 is stopped with respect to the base material W in the in-plane direction of the base material W. As shown in FIG. 5F, at time ta (1), the operation control circuit 21 sends the droplet transfer start signal Ss, the feed control circuit 38, the current switching circuit 313 of the output circuit 31, and the end determination circuit. 34 measurement circuits 341. Upon receiving the droplet transfer start signal Ss, the feed control circuit 38 sends a feed speed control signal Fc for setting the feed speed Fw to the speed fw1 to the feed mechanism 161. As a result, as shown in FIG. 5E, the consumable electrode 15 starts to be fed at the feeding speed Fw at the feeding speed Fw1. The feed speed Fw is positive in the direction from the welding torch 14 toward the base material W. The speed fw1 is, for example, 100 to 300 cm / min. As shown in FIG. 6H, at time ta (1), the pulse generation instruction signal Ps changes to the high level. As a result, the current waveform generation circuit 315 sends a current setting signal Ir1 for flowing the welding current Iw having a unit pulse waveform to the current switching circuit 313. Further, as shown in FIG. 4B, when the current switching circuit 313 receives the droplet transfer start signal Ss, the switch Sw in the current switching circuit 313 is connected to the a side. Therefore, a welding current Iw having a unit pulse waveform shown in FIG. 3C flows from time ta (1).

  As shown in FIG. 5C, the period Tf in which the welding current Iw having a unit pulse waveform flows is composed of an increase period Tu, a peak period Tp, a decrease period Td, and a base period Tb. In the increase period Tu, the welding current Iw increases to the peak current value ip. During the peak period Tp, the welding current Iw flows at the peak current value ip. In the decrease period Td, the welding current Iw decreases from the peak current value ip to the base current value ib. During the base period Tb, the welding current Iw flows at the base current value ib. In the present embodiment, the length of the base period Tb is adjusted so that the time average value of the welding voltage Vw becomes a preset voltage value vr1. Thereby, the length of the arc a1 is kept at an appropriate value. Then, the welding current Iw flows with the absolute value of the time average value at the first value ir1. In the peak period Tp, the droplet 151 grown at the tip of the consumable electrode 15 is affected by the electromagnetic pinch force. Then, the droplet 151 separates from the consumable electrode 15 and falls onto the base material W during the peak period Tp or the decrease period Td. Thus, one droplet 151 moves to the base material W during the period Tf.

  As shown in FIG. 5 (h), at time ta (2), the pulse generation instruction signal Ps again changes to the high level. As a result, the current waveform generation circuit 315 sends a current setting signal Ir1 for flowing the welding current Iw having a unit pulse waveform to the current switching circuit 313. Further, as shown in FIG. 2B, the switch Sw in the current switching circuit 313 is connected to the a side. Therefore, a welding current Iw having a unit pulse waveform shown in FIG. 5C flows from time ta (2). Similarly, a welding current Iw having a unit pulse waveform flows from time ta (3), ta (4)... Ta (n) (n is an integer). That is, in the droplet transfer period T1, a pulse current having a shape in which the unit pulse waveform is repeated a plurality of times flows. As shown in FIG. 6A, in the droplet transfer period T <b> 1, the droplet moves to the base material W and a molten pool 881 is formed in the base material W.

  During the droplet transfer period T1, the pulse generation instruction signal Ps is sent to the measurement circuit 341 in the end determination circuit 34. Further, as described above, the droplet transfer start signal Ss is sent to the measurement circuit 341 at time ta (1), which is the start time of the droplet transfer period T1. The measurement circuit 341 measures the number of times the pulse generation instruction signal Ps is received after the time when the droplet start signal Ss is received. Thereby, the measurement circuit 341 measures the number Ns of peak periods Tp in each droplet transfer period T1. Then, when the number Ns reaches the set number Nb, the comparison circuit 342 sends an end instruction signal Es to the current switching circuit 313, the feed control circuit 38, and the operation control circuit 21 in the output circuit 31. In the present embodiment, the comparison circuit 342 ends the end instruction signal at the time (time ta (n + 1)) after the period Tf from the time (time ta (n)) at which the number Ns has reached the set number Nb. Sending Es. The time at which the comparison circuit 342 sends the end instruction signal Es is not necessarily the time ta (n + 1), and may be before the time ta (n + 1). For example, the time at which the comparison circuit 342 sends the end instruction signal Es may be a time after the period Ts from the time (time ta (n)) when it is determined that the number Ns has reached the set number Nb. The set number Nb is, for example, 15-18.

<Cooling period T2>
The cooling period T2 is a period for cooling the molten pool 881 formed in the base material W. When the current switching circuit 313 receives the end instruction signal Es at time ta (n + 1), the switch Sw in the current switching circuit 313 is connected to the b side, as shown in FIGS. 4B and 5B. Thereby, the droplet transfer period T1 ends and the cooling period T2 starts. As shown in FIG. 6C, when the switch Sw in the current switching circuit 313 is connected to the b side, the welding current Iw flows with the second value ir2 as the time average value of the absolute value of the welding current Iw from the time ta (n + 1). In the present embodiment, the second value ir2 is a direct current. The second value ir2 is smaller than the first value ir1. The second value is an extremely small value such that the droplet does not migrate from the consumable electrode 15 to the base material W, and is, for example, 5 to 20A. In the present embodiment, the state where the arc a1 is generated in the cooling period T2 is continued. Therefore, it is not necessary to regenerate the arc a1 when starting the next droplet transfer period T1. On the other hand, as shown in FIGS. 4A and 5A, when the operation control circuit 21 receives the end instruction signal Es at time ta (n + 1), the operation for setting the robot moving speed VR to the speed v2. A control signal Ms is sent to the welding robot 1. As a result, the welding torch 14 holding the consumable electrode 15 moves at a speed v2 with respect to the base material W in the in-plane direction of the base material W along the welding progress direction Dr of FIGS. 6B and 7. start. The speed v2 is larger than the speed v1. The speed v2 is, for example, 50 to 150 cm / min. The welding direction Dr in each cooling period T2 is common to each other. As shown in FIG. 4E, when the feed control circuit 38 receives the end instruction signal Es, the feed control circuit 38 sends a feed speed control signal Fc for setting the feed speed Fw to the speed fw2 to the feed mechanism 161. Thereby, the consumable electrode 15 starts to be fed from the welding torch 14 toward the base material W at the speed fw2. The speed fw2 is smaller than the speed fw1, for example, 70 cm / min. As shown in FIG.6 (c), in the cooling period T2, the molten pool 881 is solidified by being cooled, and the circular welding trace 882 is formed by planar view (refer FIG. 7). When the welding torch 14 reaches a predetermined position of the base material W, the droplet transfer period T1 starts again as shown in FIG.

  As described above, welding is performed by repeating the droplet transfer period T1 and the cooling period T2. As a result, as shown in FIG. 7, a scaly bead is formed in which a plurality of circular welding marks 882 are continuous along the welding progress direction Dr.

  Next, the effect of this embodiment is demonstrated.

  In the present embodiment, when the number Ns (the number of unit pulse waveforms of the welding current Iw) of the peak period Tp in each droplet transition period T1 reaches the set number Nb, the droplet transition period T1 is terminated. Yes. One droplet 151 moves from the consumable electrode 15 to the base material W during the period Tf in which the welding current Iw having one unit pulse waveform flows. Therefore, the number of droplets 151 transferred in each droplet transfer period T1 can be made uniform. Moreover, the volume of the droplet 151 which transfers in each period Tf is substantially the same. Therefore, the size of each welding mark 882 formed on the base material W in each droplet transfer period T1 can be made uniform. Therefore, according to the present embodiment, a clean bead having a uniform width can be formed.

  In general, the period Tf, which is the period of the pulse generation instruction signal Ps sent by the signal generation circuit 316 that is a voltage frequency conversion circuit, is not a constant value but varies somewhat. Therefore, when the droplet transfer period T1 is controlled to have a certain length using the timer circuit, the number of times Ns in each droplet transfer period T1 may vary for each droplet transfer period T1. If the number of times Ns in each droplet transition period T1 varies, the number of droplets 151 that migrate in each droplet transition period T1 varies. Then, since the size of each welding mark 882 formed on the base material W in each droplet transfer period T1 varies, a clean bead having a uniform width cannot be formed. On the other hand, according to the present embodiment, as described above, the droplet transfer period T1 ends by measuring the number Ns of peak periods Tp in each droplet transfer period T1. Therefore, the number of times Ns in each droplet transfer period T1 does not vary. If the number of times Ns in each droplet transfer period T1 does not vary, the size of each welding mark 882 formed on the base material W in each droplet transfer period T1 can be made uniform as described above. Therefore, this embodiment is suitable for forming a clean bead having a uniform width.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a diagram showing an internal configuration of the arc welding system according to the present embodiment.

  An arc welding system A2 shown in FIG. 1 includes a welding robot 1, a robot control device 2, and a welding power source device 3. The arc welding system A2 is different from the above-described arc welding system A1 in that the measuring circuit 341 measures the number of times Ns, and the other points are the same. The measurement circuit 341 does not measure the number Ns of the peak period Tp based on the number of times the pulse generation instruction signal Ps is generated, but measures the number Ns based on the value of the welding current Iw detected by the current detection circuit 312. . Therefore, in the present embodiment, the current detection signal Id is sent from the current detection circuit 312 to the measurement circuit 341. The measurement circuit 341 employs, for example, the number of times Ns that the value of the welding current Iw exceeds a certain threshold value.

  According to the present embodiment, a clean bead having a uniform width can be formed for the same reason as described in the first embodiment.

  Next, a third embodiment of the present invention will be described with reference to FIGS.

  FIG. 9 is a diagram showing an internal configuration of the arc welding system according to the present embodiment. FIG. 10 is a timing chart of signals and the like in the welding method according to the present embodiment. FIG. 11 is a timing chart showing in detail a change state of each signal and the like in the droplet transfer period period T1 of FIG.

  As shown in FIGS. 10 and 11, the present embodiment is different from the first embodiment in that the welding torch 14 is moved relative to the base material W while the arc a1 is extinguished during the cooling period T2. An arc welding system A3 shown in FIG. 9 includes a welding robot 1, a robot control device 2, and a welding power source device 3. Since the welding robot 1 and the robot control device 2 in the arc welding system A3 are the same as the arc welding system A1 according to the first embodiment, the description thereof is omitted. The welding power source device 3 includes an output circuit 31, a current value storage unit 37, an end determination circuit 34, a set number storage unit 35, and a feed control circuit 38. Each configuration of the welding power source device 3 is substantially the same as the configuration in the first embodiment except for the output circuit 31 and the current value storage unit 37, and thus the description thereof is omitted.

  The current value storage unit 37 stores the third value ir3. The value of the third value ir3 is input from the teach pendant 23 and stored in the storage unit via the operation control circuit 21, for example.

  The output circuit 31 includes a power supply circuit 311, a current detection circuit 312, a current error calculation circuit EI, a current switching circuit 313, a current control circuit 319, a current waveform generation circuit 315, a signal generation circuit 316, and a voltage detection. A circuit 317, a voltage error calculation circuit EV, and a voltage control circuit 318 are included. Each configuration of the output circuit 31 is substantially the same as the configuration in the first embodiment except for the current control circuit 319, and thus the description thereof is omitted. The current control circuit 319 is for setting a value of a welding current Iw that flows during an arc generation period T0 described later. The current control circuit 319 sends a current setting signal Ir3 for allowing the welding current Iw to flow at the third value ir3 to the current switching circuit 313.

  Next, an arc welding method using the arc welding system A3 will be described with reference to FIGS. In the method according to this embodiment, the arc generation period T0, the droplet transfer period T1, and the cooling period T2 are repeated.

<Arc generation period T0 (time tg1 to time ta (1))>
[Time tg1 to Time tg2]
The arc generation period T0 starts at time tg1. As shown in FIG. 11 (e), at time tg 1, the feed control circuit 38 sets the feed speed Fw as the feed speed control signal Fc to the value fw 3 (slow-down feed speed). To the feeding mechanism 161. As a result, the consumable electrode 15 is fed from the welding torch 14 with the feeding speed Fw as the value fw3. The value fw3 is, for example, 100 to 300 cm / min. At time tg1, since consumable electrode 15 and base material W are separated from each other, as shown in FIG. 5C, during a certain period from time tg1 (time tg1 to time tg2 in this embodiment). The welding current Iw does not flow between the consumable electrode 15 and the base material W. On the other hand, as shown in FIG. 4D, from time tg1 to time tg2, a no-load voltage V0 of about 80 V, for example, is applied as the welding voltage Vw between the consumable electrode 15 and the base material W. The current control circuit 319 sends a current setting signal Ir3 to the current switching circuit 313. During time tg1 to time ta (1), the switch of the current switching circuit 313 is connected to the b side. Therefore, during the period from time tg1 to time ta (1), the current setting signal Ir3 is sent from the current switching circuit 313 to the current error calculation circuit EI as the current setting signal Ir.

  Note that, as shown in FIG. 5A, in the arc generation period T0, the robot moving speed VR is 0, and the welding torch 14 does not move along the base material W.

[Time tg2 to Time tg3]
The consumable electrode 15 is fed from the welding torch 14 and approaches the base material W, and the consumable electrode 15 and the base material W come into contact at time tg2. Then, as shown in FIG. 11 (d), the welding voltage Vw applied between the consumable electrode 15 and the base material W rapidly decreases. Further, as shown in FIG. 3C, energization of the welding current Iw from the consumable electrode 15 to the base material W is started. As described above, the current setting signal Ir3 is sent from the current switching circuit 313 to the current error calculation circuit EI as the current setting signal Ir. Therefore, the value of the welding current Iw increases rapidly so as to become the third value ir3.

[Time tg3 to Time tg4]
As shown in FIG. 11C, at time tg3, the value of the welding current Iw reaches the third value ir3. And for a while from time tg3, the welding current Iw flows at the third value ir3. During a short period from time tg3 (in the present embodiment, time tg3 to time tg4), the consumable electrode 15 and the base material W are kept in contact with each other. While the consumable electrode 15 and the base material W are in contact, a portion of the consumable electrode 15 adjacent to the base material W is melted by Joule heat.

[Time tg4 to Time ta (1)]
At time tg4, a portion of the consumable electrode 15 that is close to the base material W is melted, and an arc a1 is generated between the consumable electrode 15 and the base material W. As shown in FIG. 11D, the welding voltage Vw applied between the consumable electrode 15 and the base material W increases rapidly in the vicinity of time tg4. From time tg4 to time ta (1), the welding current Iw is kept flowing at the third value ir3. This is because the distance between the consumable electrode 15 and the base material W is set to an appropriate length.

<Droplet transfer period T1 (time ta (1) to time ta (n + 1))>
The droplet transfer period T1 starts from time ta (1). As shown in FIGS. 10 (f) and 11 (f), at time ta (1), the operation control circuit 21 sends the droplet transfer start signal Ss to the feed control circuit 38 and the current switching circuit of the output circuit 31. 313 and the measurement circuit 341 of the end determination circuit 34. Thereafter, the same process as the process in the droplet transfer period T1 of the first embodiment is performed.

  Also in the present embodiment, the pulse generation instruction signal Ps is sent to the measurement circuit 341 in the end determination circuit 34 during the droplet transfer period T1. Further, as described above, the droplet transfer start signal Ss is sent to the measurement circuit 341 at time ta (1), which is the start time of the droplet transfer period T1. The measurement circuit 341 measures the number of times the pulse generation instruction signal Ps is received after the time when the droplet transfer start signal Ss is received. Thereby, the measurement circuit 341 measures the number Ns of peak periods Tp in each droplet transfer period T1. Then, when the number of times Ns reaches the set number Nb, the comparison circuit 342 sends an end instruction signal Es to the power supply circuit 311, the current switching circuit 313, the feed control circuit 38, and the operation control circuit 21.

<Cooling period T2>
The cooling period T2 is a period for cooling the molten pool 881 formed in the base material W. As shown in FIG. 11C and FIG. 11D, when the power supply circuit 311 receives the end instruction signal Es at time ta (n + 1), the power supply circuit 311 stops, and the welding voltage Vw and the welding current Iw are set. 0 (welding current Iw is caused to flow at second value ir2 = 0A). In this way, the droplet transfer period T1 ends and the cooling period T2 starts. As shown in FIG. 5E, when the feed control circuit 38 receives the end instruction signal Es, the feed control circuit 38 sends a feed speed control signal Fc for setting the feed speed Fw to 0 to the feed mechanism 161. Thereby, the supply of the consumable electrode 15 is stopped. As shown in FIGS. 10A and 11A, when the operation control circuit 21 receives the end instruction signal Es at time ta (n + 1), the operation control signal for setting the robot moving speed VR to the speed v2. Ms is sent to the welding robot 1. As a result, the welding torch 14 holding the consumable electrode 15 starts to move at a velocity v2 with respect to the base material W along the welding progress direction Dr (see FIGS. 6 and 7) in the in-plane direction of the base material W. . In the cooling period T2, the molten pool 881 is solidified by being cooled, and a circular welding mark 882 (see FIGS. 6 and 7) is formed in plan view. When the cooling period T2 ends, the arc generation period T0 described above is started and the arc a1 is generated again.

  As described above, in this embodiment, welding is performed by repeating the arc generation period T0, the droplet transfer period T1, and the cooling period T2.

  According to the present embodiment, a clean bead having a uniform width can be formed for the same reason as described in the first embodiment.

  Next, a fourth embodiment of the present invention will be described with reference to FIG.

  FIG. 12 is a diagram showing an internal configuration of the arc welding system according to the present embodiment.

  An arc welding system A4 shown in the figure includes a welding robot 1, a robot control device 2, and a welding power source device 3. The arc welding system A4 is different from the above-described arc welding system A3 in that the measuring circuit 341 measures the number of times Ns, and the other points are the same. The measurement circuit 341 does not measure the number Ns of the peak period Tp based on the number of times the pulse generation instruction signal Ps is generated, but measures the number Ns based on the value of the welding current Iw detected by the current detection circuit 312. . Therefore, in the present embodiment, the current detection signal Id is sent from the current detection circuit 312 to the measurement circuit 341. The measurement circuit 341 employs, for example, the number of times Ns that the value of the welding current Iw exceeds a certain threshold value.

  According to the present embodiment, a clean bead having a uniform width can be formed for the same reason as described in the third embodiment.

  The scope of the present invention is not limited to the embodiment described above. The specific configuration of each part of the present invention can be changed in various ways. In the above-described embodiment, the voltage frequency conversion circuit is described as the signal generation circuit. However, the signal generation circuit may be a circuit in which an integration circuit and a comparison circuit are combined. In the above-described embodiment, an example in which the unit pulse waveform is a direct current has been described. However, an alternating current having an EN period may be used.

A1-A4 Arc welding system 1 Welding robot 11 Base member 12 Arm 13 Motor 14 Welding torch 15 Consumable electrode 151 Droplet 16 Wire feeding device 161 Feeding mechanism 19 Coil liner 2 Robot control device 21 Operation control circuit 23 Teach pendant 3 Welding Power supply device 31 Output circuit 311 Power supply circuit 312 Current detection circuit 313 Current switching circuit 314 Current control circuit 315 Current waveform generation circuit 316 Signal generation circuit 317 Voltage detection circuit 318 Voltage control circuit 33 Current value storage unit 34 Termination determination circuit 341 Measurement circuit 342 Comparison circuit 35 Set number storage unit 37 Current value storage unit 38 Feed control circuit EI Current error calculation circuit Ei Current error signal EV Voltage error calculation circuit Ev Voltage error signal Es End instruction signal Fc Feed rate control signal Fw Feed rate IB Base current storage unit ib Source current value IBR current control circuit ibr current setting signal Id current detection signal IP peak current storage part ip peak current value IPR current control circuit ipr current setting signals Ir, Ir1, Ir2 current setting signal ir1 first value ir2 second value Iw Welding current T0 Arc generation period T1 Droplet transition period T2 Cooling period TB Base period storage unit TD Decrease period storage unit Td Decrease period TM Timer circuit TP Peak period storage unit Tp Peak period tss period signal Ts period TU Increase period storage unit Tu Increase Period Ms Operation control signal Nb Set number Ns Number of times Ps Pulse generation instruction signal Ss Droplet transfer start signal SW Switching circuit Vd Voltage detection signal VR Robot movement speed Vr Voltage setting signal Vw Welding voltage W Base material

Claims (10)

A droplet transfer period for transferring a droplet from the consumable electrode to the base material while generating an arc between the consumable electrode and the base material, and a cooling period for cooling the molten pool formed in the base material are repeated. Arc welding method,
During each droplet transfer period, a current of a unit pulse waveform including a peak period in which current flows at a peak value and a base period in which current flows at a base value smaller than the peak value is transferred from the consumable electrode to the base material. A process of repeatedly flowing;
Moving the consumable electrode along the base material with respect to the base material in the welding progress direction during each cooling period;
A step of ending the droplet transfer period when the number of times of the peak period in each droplet transfer period reaches a set number. The step of repeatedly flowing includes a step of repeatedly generating a pulse generation instruction signal during each droplet transfer period, and a step of generating a unit pulse waveform each time the pulse generation instruction signal is generated,
The arc welding method according to claim 1, wherein the step of ending the droplet transfer period includes a step of measuring the number of times of the peak period based on the number of times the pulse generation instruction signal is generated.   The arc welding method according to claim 1, wherein the step of ending the droplet transfer period includes a step of measuring the number of times of the peak period based on a value of a current flowing between the consumable electrode and the base material. .   4. The method according to claim 1, further comprising a step of starting to move the consumable electrode relative to the base material along the base material when the number of times of the peak period in each droplet transfer period exceeds a set number. The arc welding method according to claim 1.   In the step of repeatedly flowing, a current is passed from the consumable electrode to the base material so that the time average value of the absolute value is the first value, and in the step of moving, a current is passed from the consumable electrode to the base material. The arc welding method according to claim 1, wherein the time average value of the absolute value is a second value smaller than the first value, and the second value is 5 to 20A.   In the step of repeatedly flowing, a current is passed from the consumable electrode to the base material so that the time average value of the absolute value is the first value, and in the step of moving, a current is passed from the consumable electrode to the base material. The arc welding method according to claim 1, wherein the time average value of the absolute value is a second value smaller than the first value, and the second value is 0A. An output circuit that alternately repeats a droplet transfer period in which a pulse current flows from the consumable electrode to the base material and a cooling period for cooling the molten pool formed in the base material,
The waveform of the pulse current is an arc welding system having a shape that repeats a unit pulse waveform including a peak period in which current flows at a peak value and a base period in which current flows at a base value smaller than the peak value,
A set number storage unit for storing the set number;
An end determination circuit that sends an end instruction signal when the number of times of the peak period in each droplet transfer period reaches the set number,
The arc welding system, wherein the output circuit ends the droplet transfer periods when receiving the end instruction signal. The output circuit includes: a signal generation circuit that repeatedly generates a pulse generation instruction signal during each droplet transfer period; and a current waveform generation circuit that generates the unit pulse waveform every time the pulse generation instruction signal is received. Including
The arc welding system according to claim 7, wherein the end determination circuit includes a measurement circuit that measures the number of times of the peak period based on the number of times the pulse generation instruction signal is generated.   The termination determination circuit includes a current detection circuit that detects a current flowing between the consumable electrode and the base material, and a measurement that measures the number of times of the peak period based on a current value detected by the current detection circuit. And an arc welding system according to claim 7. A welding robot for holding the consumable electrode;
An operation control circuit for sending an operation control signal to the welding robot,
10. The operation control circuit according to claim 7, wherein when receiving the end instruction signal, the operation control circuit sends a signal for moving the consumable electrode relative to the base material along the base material as the operation control signal. The arc welding system according to the above.

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