Arc welding control method and arc welding apparatus

Abstract

To provide an arc welding method using a robot, which suppresses the occurrence of welding accompanied by the retraction movement of the robot after the end of welding.SOLUTION: In the arc-welding control method in which the welding wire is fed and welded by using the robot, when the welding is completed at time t2, the welding wire is retracted and fed (Fw) by a retraction distance during a period of time t3 to t4, and the robot starts retreating and moving (Vr) from the welding end position after the retraction feeding is completed at time t4.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an arc welding control method and an arc welding apparatus that uses a robot to feed a welding wire for welding. [Background technology]

[0002] An arc welding method is used in which a robot is used to feed a welding wire for welding. In the arc welding method, welding begins when the robot arrives at a welding start position, moves along the welding line during welding, and ends welding when the robot reaches a welding end position, after which the robot starts to retreat from the welding end position.

[0003] In the invention of Patent Document 1, when the robot reaches the welding start position and detects that welding has started with the welding wire in contact with the base material, it reverses the welding wire at the welding end position just before the welding start position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-219085 Summary of the Invention [Problem to be solved by the invention]

[0005] When welding is completed and the robot starts to retreat from the welding completion position, the retreating movement may cause the shape of the conduit cable, which serves as the wire feed path, to change, which may cause the welding wire to protrude forward and become welded to the molten pool. When this occurs, welding must be interrupted to remove the weld, which reduces production efficiency.

[0006] Therefore, an object of the present invention is to provide an arc welding control method and an arc welding device that can suppress the occurrence of welding that occurs, for example, when the robot retreats after welding is completed. [Means for solving the problem]

[0007] A first aspect of the present invention provides an arc welding control method for using a robot to feed a welding wire for welding, characterized in that, when welding is completed, the welding wire is fed backward by a backward feed distance, and the robot starts a retreat movement from a welding completion position after the backward feed is completed.

[0008] As an example, the arc welding control method of the present invention is characterized in that the retraction distance is set in accordance with the length of the feed path.

[0009] As an example, the arc welding control method of the present invention is characterized in that the retraction distance is set in accordance with the diameter of the welding wire.

[0010] As an example, the arc welding control method of the present invention is characterized in that the retraction distance is set in accordance with the distance between the power feed tip and the base metal.

[0011] As an example, the arc welding control method of the present invention is characterized in that, when adhesion between the welding wire and the molten pool occurs after the robot starts the retreat movement, the retreat distance is increased from the next welding.

[0012] A second aspect of the present invention provides an arc welding apparatus that uses a robot to feed a welding wire for welding, characterized in that the arc welding apparatus retracts the welding wire by a retraction distance when welding is completed, and the robot starts retracting from the welding completion position after the retraction feed is completed. [Effects of the Invention]

[0013] According to the above configuration, for example, in the arc welding control method and arc welding apparatus, it is possible to prevent welding from occurring when the robot retreats after welding is completed, thereby suppressing a decrease in production efficiency. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram of an arc welding device according to an embodiment of the present invention. [Figure 2] 2 is a timing chart of signals in the arc welding device of FIG. 1, illustrating an arc welding control method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a block diagram of an arc welding device according to an embodiment of the present invention, and each block will be described below with reference to the drawing.

[0017] The sequence circuit SC receives a welding start signal St and a rearward feed period setting signal Trr, which will be described later, as inputs, performs the following processing, and outputs a sequence signal Sc. When welding is complete, the sequence signal Sc=0. 1) During steady welding when the welding start signal St is at a high level, the sequence signal Sc=1 is output. 2) A sequence signal Sc=2 is output during a predetermined anti-stick period (approximately 200 ms) from the time when the welding start signal St changes to low level. 3) During the following predetermined pause period (approximately 10 ms), a sequence signal Sc=3 is output. 4) During the subsequent backward feeding period determined by the backward feeding period setting signal Trr, the sequence signal Sc=4 is output. 5) During the subsequent predetermined initial evacuation period (approximately 100 ms), a sequence signal Sc=5 is output. 6) When the initial evacuation period ends, the sequence signal Sc=0 (welding completed state) is output.

[0018] The wire feed length setting circuit LFR is a touch panel or the like provided on the front panel of the welding power source PS. When the welding operator inputs the length of the wire feed path for the welding wire 1 from the wire feeder WF to the power feed tip in the welding torch AT, the circuit outputs the input value as a wire feed length setting signal Lfr. The wire feed length setting signal Lfr is, for example, in the range of 10 cm to 300 cm. Because the welding wire 1 is fed through a conduit cable, the length of the wire feed path is also the length of the conduit cable.

[0019] The welding wire diameter setting circuit DR is a touch panel or the like provided on the front panel of the welding power source PS, and when the welding operator selects the diameter of the welding wire 1 to be used, it outputs a welding wire diameter setting signal Dr corresponding to the selection. The welding wire diameter is, for example, in the range of 0.8 mm to 1.6 mm. Therefore, the value of the welding wire diameter setting signal Dr is 1 when the diameter is 1.6 mm, 2 when it is 1.2 mm, 3 when it is 1.0 mm, 4 when it is 0.9 mm, and 5 when it is 0.8 mm.

[0020] The power contact point-to-base metal distance setting circuit ER is a touch panel or the like provided on the front panel of the welding power source PS, and when the welding operator inputs the power contact point-to-base metal distance, the circuit outputs the value as a power contact point-to-base metal distance setting signal Er. The power contact point-to-base metal distance setting signal Er is in the range of, for example, 10 mm to 30 mm.

[0021] The retraction distance setting circuit LRR receives the above-mentioned feed path length setting signal Lfr, the above-mentioned welding wire diameter setting signal Dr, and the above-mentioned power feed tip-to-base metal distance setting signal Er as inputs, performs calculations according to the following equation (1), and outputs a retraction distance setting signal Lrr. The standard value in the equation below is, for example, 2.5 mm. Lrr [mm] = Standard value + Lfr [cm] × 0.005 + Dr × 0.2 + Er [mm] × 0.04 (1) 1) Correction by the feeding path length setting signal Lfr The longer the wire feed path length, the greater the amount of welding wire 1 protruding forward from the tip of the power feed tip due to changes in the shape of the conduit cable as the robot retreats. The value of Lfr ranges from 10 cm to 300 cm. Therefore, a correction is made by adding (Lfr x 0.005) to the standard value. As a result, the longer the Lfr value, the greater the additional value, and the larger the correction is made so that the retract distance setting signal Lrr is increased. 2) Correction by welding wire diameter setting signal Dr As the diameter of the welding wire becomes smaller, the amount by which the welding wire 1 protrudes forward from the tip of the power contact tip increases due to changes in the shape of the conduit cable as the robot retreats. The value of Dr is 1 when the diameter is 1.6 mm, 2 when it is 1.2 mm, 3 when it is 1.0 mm, 4 when it is 0.9 mm, and 5 when it is 0.8 mm. Therefore, a correction is made by adding (Dr x 0.2) to the standard value. As the diameter becomes smaller and the value of Dr increases, the additional value increases, correcting the retract distance setting signal Lrr to be larger. 3) Correction by the power supply tip-workpiece distance setting signal Er The longer the distance between the contact tip and the workpiece, the greater the amount of welding wire 1 protruding forward from the tip of the contact tip due to changes in the shape of the conduit cable as the robot retreats. The value of Er is in the range of 10 mm to 30 mm. Therefore, a correction is made by adding (Er x 0.04) to the standard value. As a result, the longer the value of Er, the greater the additional value becomes, and the correction is made so that the retract distance setting signal Lrr becomes larger.

[0022] The reverse distance control setting circuit LCR receives the reverse distance setting signal Lrr and a welding determination signal Sd (described later) as inputs, and when the welding determination signal Sd is at a high level, adds a predetermined increment to the value of the reverse distance setting signal Lrr and outputs a reverse distance control setting signal Lcr (e.g., 2 mm).

[0023] The backward feed period setting circuit TRR receives the above-mentioned backward distance control setting signal Lcr as an input, performs the calculation according to the following equation, and outputs a backward feed period setting signal Trr. The backward feed speed in the equation below is, for example, 12 m / min. In this case, if Lcr=5 mm, then Trr=25 ms. Trr[ms]=(Lcr[mm] / (reverse feed speed [m / min]×1000 / 60))×1000

[0024] The start circuit ON receives the sequence signal Sc as input and outputs a start signal On that goes high when the sequence signal Sc is 1 (steady welding period), 2 (anti-stick period) or 5 (initial evacuation period).

[0025] The voltage setting circuit VR receives the sequence signal Sc as an input and outputs a voltage setting signal Vr which becomes the steady-state voltage setting value when the sequence signal Sc=1 (steady-state welding period), the anti-stick voltage setting value when the sequence signal Sc=2 (anti-stick period), and the welding determination voltage setting value when the sequence signal Sc=5 (initial evacuation period).

[0026] The feed speed setting circuit FR receives the sequence signal Sc as an input and outputs a feed speed setting signal Fr which is the steady feed speed setting value when the sequence signal Sc=1 (steady welding period), 0 when the sequence signal Sc=2 (anti-stick period) and 3 (rest period), the retreat feed speed setting value when the sequence signal Sc=4 (retreat feed period), and 0 when the sequence signal Sc=5 (initial retreat period).

[0027] The welding determination circuit SD receives the above sequence signal Sc and the welding voltage Vw between the output terminals of the welding power source PS as inputs, and when the sequence signal Sc=5 (initial evacuation period) and the value of the welding voltage Vw is equal to or less than the contact determination value (approximately 5 V), it determines that welding has occurred between the welding wire 1 and the molten pool and outputs a welding determination signal Sd that goes to a high level.

[0028] The welding power source PS receives the start signal On and the voltage setting signal Vr as inputs, and when the start signal On is at a high level, performs constant voltage control based on the voltage setting signal Vr, outputs a welding voltage Vw and a welding current Iw, and generates an arc 3 between the welding wire 1 and the base material 2 (molten pool).

[0029] The feeder WF receives the sequence signal Sc and the feed speed setting signal Fr as inputs, and feeds the welding wire 1 at the feed speed Fw set by the feed speed setting signal Fr when the sequence signal Sc=1 to 5.

[0030] The welding torch AT supplies the above-mentioned welding current Iw and welding voltage Vw to the welding wire 1 and ejects shielding gas onto the area where the arc 3 is generated, thereby performing arc welding.

[0031] The robot control device RC receives the sequence signal Sc as input, moves the robot RM from the welding start position along the welding line to the welding end position in accordance with a pre-taught work program, and when the sequence signal Sc changes to 5, outputs an operation control signal Mc for moving the robot RM away from the welding end position, and also outputs a welding start signal St that is at a high level during the period when the robot RM is moving from the welding start position to the welding end position.

[0032] The robot RM is equipped with the above-mentioned feeder WF and the above-mentioned welding torch AT, and receives the above-mentioned operation control signal Mc as an input to move the tip position of the welding torch AT along the weld line.

[0033] 2 is a timing chart of signals at the end of welding in the arc welding apparatus of FIG. 1, which illustrates an arc welding control method according to an embodiment of the present invention. (A) in FIG. 2 shows the change over time of the welding start signal St, (B) in FIG. 2 shows the change over time of the start signal On, (C) in FIG. 2 shows the change over time of the average value Vav of the welding voltage Vw, (D) in FIG. 2 shows the change over time of the average value Iav of the welding current Iw, (E) in FIG. 2 shows the change over time of the feed speed Fw, and (F) in FIG. 2 shows the change over time of the robot movement speed vr. The operation of each signal will be explained below with reference to the figure.

[0034] When the arc welding method is short-circuit transfer arc welding, the state is one in which short-circuit periods and arc periods alternate. The instantaneous value of the welding voltage Vw is nearly 0 V during the short-circuit period and approximately 30 V during the arc period. The instantaneous value of the welding current Iw gradually increases during the short-circuit period and gradually decreases during the arc period. When the arc welding method is pulse arc welding, the state is one in which peak periods and base periods alternate. The instantaneous value of the welding voltage Vw is a peak voltage value of approximately 30 V during the peak period and a base voltage value of approximately 25 V during the base period. The instantaneous value of the welding current Iw is a peak current value of approximately 500 A during the peak period and a base current value of approximately 50 A during the base period. When the feed speed Fw shown in Figure 1(E) is a positive value above 0, it is in a forward feed state, and when it is a negative value below 0, it is in a backward feed state.

[0035] (1) Operation during steady welding period before time t1 The period before time t1 is the steady-state welding period, and the sequence signal Sc in FIG. 1 is set to 1. As shown in FIG. 1(A), the welding start signal St from the robot control device RC in FIG. 1 is at a high level, and as shown in FIG. 1(B), the start signal On is also at a high level. As shown in FIG. 1(C), the welding voltage average value Vav is controlled based on the steady-state voltage setting value of the voltage setting signal Vr in FIG. 1, and has a waveform of approximately a constant value of approximately 20 to 40 V. As shown in FIG. 1(D), the welding current average value Iav corresponds to the steady-state feed speed setting value of the feed speed setting signal Fr in FIG. 1, and has a waveform of approximately a constant value of approximately 100 to 400 A. As shown in FIG. 1(E), the feed speed Fw is set by the steady-state feed speed setting value of the feed speed setting signal Fr in FIG. 1, and is approximately 3 to 10 m / min. As shown in FIG. 1(F), the robot movement speed vr is approximately 30 to 150 cm / min.

[0036] (2) Operation during the anti-stick period from time t1 to time t2 At time t1, when the robot RM in FIG. 1 reaches the welding end position and stops, as shown in FIG. 1A, the welding start signal St changes to low level, the sequence signal Sc in FIG. 1 becomes 2, and the predetermined anti-stick period from time t1 to t2 begins. As shown in FIG. 1B, the start signal On continues to be high level. As shown in FIG. 1C, the welding voltage average Vav is controlled based on the anti-stick voltage setting value of the voltage setting signal Vr in FIG. 1 and is maintained at a constant value approximately 5 V lower than that during steady welding. As shown in FIG. 1D, the welding current average Iav decreases over time as the feed rate Fw gradually decelerates to 0 A, reaching approximately 0 A at time t2. As shown in FIG. 1E, the feed rate Fw gradually decelerates due to inertia as the feed rate setting signal Fr in FIG. 1 becomes 0, reaching approximately 0 A at time t2. As shown in FIG. 1F, the robot movement velocity vr stops and reaches 0 A at time t1. During this anti-stick period, the tip of the welding wire burns up, and at time t2, it is separated from the molten pool by about 3 mm.

[0037] (3) Operation during the pause period from time t2 to time t3 When the anti-stick period ends at time t2, the sequence signal Sc in FIG. 1 becomes 3, and a predetermined pause period begins from time t2 to t3. As shown in FIG. 1(B), the start signal On changes to low level. In response to this, as shown in FIG. 1(C), the welding voltage average value Vav becomes 0 V because output control stops. As shown in FIG. 1(D), the welding current average value Iav also becomes 0 A. As shown in FIG. 1(E), the feed speed Fw also becomes 0.

[0038] (4) Operation during the backward feeding period from time t3 to t4 When the pause period ends at time t3, the sequence signal Sc in FIG. 1 becomes 4, and the rearward feed period from time t3 to t4 begins. As shown in FIG. 1B, the start signal On remains at a low level. As shown in FIG. 1C, the welding voltage average Vav becomes 0 V, and as shown in FIG. 1D, the welding current average Iav becomes 0 A. As shown in FIG. 1E, the feed rate Fw becomes the rearward feed rate set value of the feed rate setting signal Fr in FIG. 1, which becomes a negative rearward feed rate. The welding wire is then rearward fed by the rearward feed distance during the rearward feed period from time t3 to t4. The rearward feed distance is set by the rearward distance setting signal Lrr in FIG. 1, and is set by inputting the feed path length setting signal Lfr, welding wire diameter setting signal Dr, and power feed tip-to-base metal distance setting signal Er in FIG. 1 into Equation (1) above. In other words, the rearward feed distance is adjusted to an optimal value depending on the length of the feed path, the welding wire diameter, and the power feed tip-to-base metal distance. The reason for making such corrections is that the amount by which the welding wire protrudes forward when the robot RM retreats varies depending on these conditions. In this embodiment, the retreat distance is corrected using the above three parameters, but it may also be corrected using at least one parameter.

[0039] (5) Operation during the initial evacuation period from time t4 to t5 When the backward feed period ends at time t4, the sequence signal Sc in FIG. 1 becomes 5, and the predetermined initial retreat period from time t4 to t5 begins. As shown in FIG. 1B, the start signal On becomes high again. As shown in FIG. 1C, the welding voltage average value Vav is controlled based on the welding determination voltage setting value of the voltage setting signal Vr in FIG. 1 and becomes the welding determination voltage value. As shown in FIG. 1D, the welding current average value Iav becomes 0 A because no arc is generated. As shown in FIG. 1E, the feed speed Fw becomes 0 when the feed speed setting signal Fr in FIG. 1 becomes 0, and feeding stops. As shown in FIG. 1F, the robot movement speed vr becomes the predetermined retreat movement speed because the robot RM starts retreating. At time t4, the welding wire protrudes forward due to a change in the shape of the conduit cable as the robot RM starts retreating. However, since the welding wire is fed backward by an appropriate length during the backward feed period, it is possible to prevent the tip of the welding wire from coming into contact with the molten pool and causing welding.

[0040] During the initial retraction period, the welding voltage average value Vav is set to the welding determination voltage value. This welding determination voltage value is set to approximately 10 V, a value at which no arc occurs. Therefore, in the extremely rare case where the welding wire protrudes forward so much that it comes into contact with the molten pool and causes welding, the welding determination signal Sd in FIG. 1 goes high. When the welding determination signal Sd goes high, the retraction distance is corrected to a value set by the retraction distance control setting signal Lcr in FIG. 1, which is obtained by adding a predetermined increase value to the value of the retraction distance setting signal Lrr in FIG. 1. As a result, the retraction distance is increased from the next welding, thereby preventing welding from occurring.

[0041] (6) Welding end state behavior after time t5 When the initial evacuation period ends at time t5, the sequence signal Sc in Figure 1 becomes 0, and the welding ends. As shown in Figure 1(B), the start signal On becomes low level. As shown in Figure 1(C), the welding voltage average value Vav becomes 0 V, and as shown in Figure 1(D), the welding current average value Iav becomes 0 A. As shown in Figure 1(E), the feed speed Fw becomes 0, and the feed stops. As shown in Figure 1(F), the robot movement speed vr remains the evacuation movement speed, so the evacuation movement continues.

[0042] The effects of this embodiment are described below. According to this embodiment, in an arc welding control method using a robot to feed a welding wire for welding, when welding is completed, the welding wire is fed backward by a retreat distance, and the robot starts retracting from the welding end position after the retreat feed is completed. In conventional technology, when welding is completed and the robot starts retracting from the welding end position, the retreat movement can cause the welding wire to protrude forward and become welded to the molten pool due to a change in the shape of the conduit cable that serves as the feed path. When this adhesion occurs, welding must be interrupted and work performed to remove the adhesion, resulting in a decrease in production efficiency. In contrast, in this embodiment, when welding is completed, the welding wire is fed backward by a retreat distance, and the robot starts retracting from the welding end position after the retreat feed is completed. In this manner, even if the welding wire protrudes forward when the robot starts retracting, it will not be welded to the molten pool, thereby preventing a decrease in production efficiency.

[0043] More preferably, according to this embodiment, the retraction distance is set according to the length of the feed path. As the feed path becomes longer, the amount by which the welding wire protrudes forward increases due to changes in the shape of the conduit cable accompanying the retraction movement of the robot. In this embodiment, the retraction distance is corrected to be longer as the feed path becomes longer. In this way, even if the feed path becomes longer and the amount by which the welding wire protrudes forward increases, the retraction distance is longer, so the occurrence of welding can be suppressed.

[0044] More preferably, according to this embodiment, the retraction distance is set according to the diameter of the welding wire. As the diameter of the welding wire becomes smaller, the amount by which the welding wire protrudes forward increases due to a change in the shape of the conduit cable accompanying the retraction movement of the robot. In this embodiment, the retraction distance is corrected so that it becomes longer as the diameter of the welding wire becomes smaller. In this way, even if the diameter of the welding wire becomes smaller and the amount by which the welding wire protrudes forward increases, the retraction distance is longer, so that welding can be suppressed.

[0045] More preferably, according to this embodiment, the retraction distance is set in accordance with the distance between the power feed tip and the base metal. As the distance between the power feed tip and the base metal increases, the amount by which the welding wire protrudes forward increases due to changes in the shape of the conduit cable as the robot retracts. In this embodiment, the retraction distance is corrected so that it increases as the distance between the power feed tip and the base metal increases. In this way, even if the distance between the power feed tip and the base metal increases and the amount by which the welding wire protrudes forward increases, the retraction distance is long, so it is possible to prevent welding.

[0046] More preferably, according to this embodiment, if adhesion between the welding wire and the molten pool occurs after the robot has started its retraction movement, the retraction distance is increased from the next welding. Even if the robot starts its retraction movement after retracting the welding wire, there are rare cases where the welding wire protrudes forward too far and adhesion occurs. In this embodiment, if adhesion occurs, the retraction distance is increased from the next welding. This can reliably prevent the rare occurrence of adhesion.

[0047] Furthermore, according to this embodiment, in an arc welding apparatus that uses a robot to feed a welding wire for welding, the arc welding apparatus feeds the welding wire backward by a backward distance when welding is completed, and the robot starts to retreat from the welding completion position after the backward feed is completed. The arc welding apparatus according to this embodiment achieves the above-mentioned effects. [Explanation of symbols]

[0048] 1: welding wire, 2: base metal (molten pool), 3: arc, AT: welding torch, DR: welding wire diameter setting circuit, Dr: welding wire diameter setting signal, ER: contact tip-base metal distance setting circuit, Er: contact tip-base metal distance setting signal, FR: feed rate setting circuit, Fr: feed rate setting signal, Fw: feed rate, Iav: welding current average value, Iw: welding current, LCR: retraction distance control setting circuit, Lcr: retraction distance control setting signal, LFR: feed path length setting circuit, Lfr: feed path length setting signal, LRR: retraction distance setting circuit , Lrr: Retract distance setting signal, Mc: Operation control signal, ON: Start circuit, On: Start signal, PS: Welding power source, RC: Robot control device, RM: Robot, SC: Sequence circuit, Sc: Sequence signal, SD: Welding determination circuit, Sd: Welding determination signal, St: Welding start signal, TRR: Retract feed period setting circuit, Trr: Retract feed period setting signal, Vav: Welding voltage average value, Vav: Welding voltage average value, VR: Voltage setting circuit, Vr: Voltage setting signal, vr: Robot movement speed, Vw: Welding voltage, WF: Feeder

Claims

1. 1. A method for controlling arc welding in which a robot is used to feed a welding wire for welding, comprising: an arc welding control method comprising: when welding is completed, feeding the welding wire backward by a backward distance; and after the backward feeding is completed, the robot starts to move away from the welding completion position.

2. 2. The method for controlling arc welding according to claim 1, wherein the retraction distance is set in accordance with the length of the feed path.

3. 3. The arc welding control method according to claim 1, wherein the retraction distance is set in accordance with a diameter of the welding wire.

4. 3. The method for controlling arc welding according to claim 1, wherein the retraction distance is set in accordance with a distance between the power feed tip and the base metal.

5. 3. The arc welding control method according to claim 1, wherein when adhesion between the welding wire and the molten pool occurs after the robot starts the retreat movement, the retreat distance is increased from the next welding.

6. In an arc welding device that uses a robot to feed a welding wire for welding, the arc welding device retracts the welding wire by a retraction distance when welding is completed, and the robot starts retracting from the welding completion position after the retraction feed is completed.

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