JP4490011B2 - Arc start control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of an arc start control method in consumable electrode gas shielded arc welding.
[0002]
[Prior art]
FIG. 1 is a configuration diagram of a welding apparatus for performing consumable electrode gas shield arc welding. Hereinafter, each component will be described with reference to FIG.
When a welding start signal As is input from a welding start circuit AS provided outside, the welding power source device PS outputs a welding voltage Vw and a welding current Iw suitable for welding, and also feeds the welding wire 1 to the feed motor WM. The feed control signal Fc for feeding is output by The welding start circuit AS corresponds to a torch switch attached to the welding torch, a circuit in a control device that controls the welding process, and the like. The welding wire 1 is fed through a liner in the welding torch 4 as the feeding roll 5 directly connected to the feeding motor WM rotates, and the contact tip 4a attached to the tip of the welding torch 4 is used. Is fed, and an arc is generated between the welding wire 1 and the base material 2 to perform welding. At this time, when the feed roll 5 rotates forward, the welding wire 1 is fed forward in a direction approaching the base material 2, and conversely, when the feed roll rotates reversely, the welding wire 1 moves backward in a direction away from the base material 2. Be paid. The wire tip / base material distance Lw represents the distance between the tip of the welding wire 1 and the base material 2 and is substantially equal to the arc length in the arc generation state. In the normal arc start control of the prior art 1 to be described later, the welding wire is only forward fed, and in the retract arc start control of the prior art 2 to be described later, the welding wire is both forward fed and backward fed.
[0003]
[Prior art 1]
In the prior art 1, when a welding start signal is input, the welding wire is fed forward to the base material, and when the welding wire contacts or approaches the base material, a steady welding current is supplied to generate a steady arc. This is a control method (hereinafter referred to as normal arc start control). The normal arc start control will be described below with reference to the drawings.
[0004]
FIG. 2 is a timing chart of each signal of the normal arc start control. (A) shows the time change of the welding start signal As, (B) shows the time change of the feed control signal Fc, (C) shows the time change of the welding current Iw, (D) shows the time change of the wire tip / base material distance Lw, and FIGS. (E1) to (E4) show the state of the arc generating portion at each time.
[0005]
(1) Period from time t1 to t2
At time t1, when the welding start signal As is input (High level) as shown in FIG. 9A, the value of the feed control signal Fc is set to the initial feed speed as shown in FIG. The set value Fsi is set, and feeding of the welding wire is started at a speed slower than a steady feed speed set value Fs described later. At the same time, although not shown, the output of the welding power source is also started, and a welding voltage is applied between the welding wire and the base material. During this period, as shown in FIG. 4D, the wire tip / base material distance Lw gradually decreases at a speed corresponding to the initial feed speed set value Fsi.
[0006]
(2) Period after time t2
At time t2, as shown in the figure (E2), when the tip of the welding wire comes into contact with the base material or approaches a very short distance, as shown in the figure (E3), an arc 3 is generated, As shown in FIG. 3C, a steady welding current is applied. In response to this, as shown in FIG. 5B, the value of the feed control signal Fc becomes the steady feed speed set value Fs, and the welding wire is fed at a speed corresponding to this set value. And as shown in the figure (D), the arc length (distance Lw between the tip of the wire and the base metal) is appropriate as shown in the figure (E4) through a transitional period from the time t2 to the time t3. It becomes the steady arc length.
[0007]
The arc start of the consumable electrode gas shield arc welding is performed by the normal arc start control described above. However, when the material of the welding wire is aluminum or stainless steel, it is known that in this normal arc start control, an arc break or a short-circuit state is likely to occur immediately after the arc start, and a defective arc start is likely to occur. ing. In addition, when the material of the welding wire is steel, the arc start property is almost good, but when the diameter of the welding wire is as thin as 0.8 to 1.0 [mm] and as thick as 1.6 [mm]. Sometimes, the arc start performance is worse than when the diameter is 1.2 [mm]. Furthermore, the arc start performance is also deteriorated when the welding current value is low (the feeding speed is slow). That is, in the normal arc start control, the arc start performance may be deteriorated depending on the welding conditions such as the type (material and diameter) of the welding wire and the feeding speed. In order to solve this problem, the retract arc start control of prior art 2 described below has been proposed.
[0008]
[Prior Art 2]
FIG. 3 is a timing chart of each signal of the retract arc start control. (A) shows the time change of welding start signal As, (B) shows the time change of feed control signal Fc, and (C) shows the short-circuit state between the welding wire and the base metal. (D) shows the time change of the welding current Iw, FIG. (E) shows the time change of the distance Lw between the wire tip and the base material, and FIG. ) To (F5) indicate the state of the arc generating portion at each time. In the figure, the operation during the period from time t1 to t2 is the same as that in FIG. Hereinafter, the operation in the period after time t2 will be described with reference to FIG.
[0009]
(1) Period from time t2 to t3
During the period from the time t1 to the time t2, the welding wire is fed forward to the base material at a speed corresponding to the initial feeding speed set value Fsi, and at the time t2, as shown in FIG. Is in contact with the base material, as shown in FIG. 3D, an initial current Is set in advance of about several [A] to several tens [A] is energized. In response to this, as shown in FIG. 5B, the value of the feed control signal Fc changes to a predetermined reverse feed speed setting value Fsr, and the welding wire corresponds to this set value. It is fed backwards from the base material at a speed to do. Here, when the value of the feed control signal Fc is a positive value, the welding wire is fed forward, and when it is a negative value, it is fed backward. At the same time, at time t2, as shown in FIG. 5C, the welding wire and the base material are brought into contact with each other, so that the short circuit determination signal Sd changes to the high level (short circuit). During this period, the welding wire is fed backward, but the time for the feeding motor to switch from forward rotation to reverse rotation and the time for backward feeding of the play of the welding wire due to the bending of the welding torch. Due to the delay, the wire tip / base material distance Lw remains in contact with 0 [mm] as shown in FIG.
[0010]
(2) Period from time t3 to t4
At time t3, as shown in FIG. 5F3, when the wire tip is separated from the base metal by the above-described backward feeding, an initial arc 3a in which the initial current Is is energized is generated. At this time, as shown in FIG. 5C, the short circuit determination signal Sd determines the occurrence of the initial arc 3a, but remains at the high level until time t4 when the predetermined off-delay delay time Td elapses. Therefore, during this period, the backward feeding is continued, and the distance Lw between the wire tip and the base material becomes longer with time as shown in FIG.
[0011]
(3) Period after time t4
At time t4, when the delay time Td elapses and the short-circuit determination signal Sd becomes a low level as shown in FIG. 10C, the value of the feed control signal Fc is set in advance as shown in FIG. It changes to the fixed feed rate set value Fs of a predetermined positive value, and the welding wire is fed forward again at a speed corresponding to this set value. At the same time, as shown in FIG. 4D, a steady welding current is applied, and at time t5, as shown in FIG. 5E, the wire tip / base material distance Lw becomes a steady arc length, As shown in FIG. 5F5, the process proceeds to the steady arc 3b.
[0012]
As described above, in the retract arc start control, the tip of the welding wire is once brought into contact with the base material, and then the welding wire is fed backward to reliably generate the initial arc, and the welding wire is fed forward again. Transition to a steady arc. According to this method, it is possible to always obtain a good arc start performance regardless of the welding conditions such as the material, diameter and feed speed of the welding wire.
[0013]
[Problems to be solved by the invention]
As described above, in the normal arc start control of the prior art 1, when the material of the welding wire is aluminum or stainless steel, the diameter of the welding wire is smaller or larger than 1.2 [mm] and the feeding speed However, when the welding current average value is low and the arc start property is low, the welding operation may be interrupted due to the arc start failure, and the welding quality may be deteriorated.
[0014]
Further, as described above, in the retract arc start control of the prior art 2, it is possible to always obtain a good arc start performance regardless of the welding conditions such as the material of the welding wire, the diameter, and the feeding speed. However, this retract arc start control has the following problems to be solved.
▲ 1 ▼ It takes a long time to start the arc
In the normal arc start control, as described above with reference to FIG. 2, after the welding wire comes into contact with the base material at time t2, a steady arc state is reached at time t3. The period is t3. On the other hand, in the retract arc start control, as described above with reference to FIG. 3, after the welding wire comes into contact with the base material at the time t2, the period of the backward feeding at the time t2 to t4 and the steady feeding at the time t4 to t5 are performed. Since the transition period to the arc is necessary, the time required for the arc start after the contact is from time t2 to t5, which is longer than that during the normal arc start control. By the way, in welding parts such as automobiles and electronic devices, a welding portion having a short welding length is often performed many times for one workpiece. In the case of welding such a workpiece, the production efficiency decreases as the time required for each arc start increases. Therefore, the retract arc start control has a problem that the production efficiency is lowered because it takes a longer time to start the arc than the normal arc start control.
[0015]
(2) The service life of consumable parts of the feed motor and welding torch is shortened
In the retract arc start control, as described above with reference to FIG. 3, the feeding motor is rotated forward during time t1 to t2 to feed the welding wire forward, and during the subsequent time t2 to t4, the feeding motor. Is rotated backward to feed the welding wire backward, and during the subsequent period after time t4, the feeding motor is rotated forward again to forwardly feed the welding wire. In this way, since the feed motor repeats forward / reverse rotation for each arc start, the service life is shortened as compared with the normal arc start control in which only forward rotation is performed. Also, in order to repeat forward / backward feeding of the welding wire at each arc start, a coil liner for passing the welding wire inserted into the welding torch, and a contact for supplying power to the welding wire attached to the tip of the welding torch Wear of consumable parts such as chips is accelerated and the replacement cycle is shortened. As described above, in the retract arc start control, the consumable parts of the feed motor and the welding torch (hereinafter referred to as consumable parts) have a short service life. Increased replacement work time was a problem.
Therefore, the present invention provides an arc start control method for solving the above-mentioned problems of the normal arc start control and the retract arc start control.
[0016]
[Means for Solving the Problems]
The first invention is shown in FIG. And FIG. As shown in
When the welding start signal As is input, the welding wire is fed forward to the base material, and when the welding wire comes into contact with the base material, an initial current Is having a small current value is energized and the welding wire is fed backward from the base material, Retract arc start control in which the welding wire is separated from the base metal by this backward feeding and the welding wire is fed forward again after the initial arc 3a is generated, and a steady welding current is energized to shift to the steady arc 3b.
When the welding start signal As is input, the welding wire is forwardly fed to the base material, and when the welding wire comes into contact with the base material, a normal arc start control for generating a steady arc by energizing a steady welding current is provided. ,
Arc start selection signal Sc set in response to the welding stop time Tm from the previous welding end time to the current welding start time point This is an arc start control method of consumable electrode gas shield arc welding in which the arc is started by switching between the retract arc start control and the normal arc start control.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Examples 1 to 5 will be described below with reference to the drawings as examples of embodiments of the present invention.
[Example 1]
The invention of Embodiment 1 includes retract arc start control and normal arc start control, and the above-described retract arc start control by an arc start selection signal Sc selected according to welding conditions such as the type of welding wire and the feeding speed. This is an arc start control method in which an arc start is performed by switching the normal arc start control. For example, when the material of the base material is aluminum or stainless steel, since the arc start property is poor, the arc start selection signal is set to the high level and the retract arc start control is selected. In addition, since the arc start performance is good when the base material is steel, the arc start selection signal Sc is set to a low level to improve the production efficiency and extend the life of consumable parts. Select start control. Furthermore, the base material is steel, one of the two welding locations has a slow feeding speed (low average welding current), and the other welding location has a high feeding speed (average welding current) When welding the former welding point, the arc start selection signal Sc is set to a high level and the retraction arc start control is selected to improve the arc start property, and when the latter welding point is welded. Since the arc start performance is good, the normal arc start control is selected by setting the arc start selection signal Sc to the low level in order to improve production efficiency and extend the life of consumable parts. Further, according to the required level of the welding quality of the base metal welding point, when very high quality is required, the arc start selection signal Sc is set to the high level and the retract arc start control is selected. Otherwise, the arc start selection signal Sc can be set to a low level to select normal arc start control. Hereinafter, the invention of Example 1 will be described in detail with reference to the drawings.
[0022]
FIG. 4 is a block diagram of a welding power source apparatus PS for carrying out the invention of the first embodiment. Hereinafter, a description will be given with reference to FIG.
The output control circuit INV receives a commercial power supply (three-phase 200 [V], etc.) as input and performs output control such as inverter control and thyristor control according to a drive signal Dv described later, and a welding current Iw and welding voltage Vw suitable for welding. Is output.
[0023]
The welding start circuit AS is provided in a welding torch, a welding process control device, etc., and outputs a welding start signal As. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The energization determination circuit CD receives the current detection signal Id and outputs an energization determination signal Cd that is at a high level when the welding current Iw is energized and is at a low level when the energization is not energized. The initial feed speed setting circuit FSI outputs a predetermined initial feed speed setting signal Fsi. The feed speed switching circuit SF switches to the a side when the energization determination signal Cd is at a low level (non-energization), and outputs the initial feed speed setting signal Fsi as the feed speed control setting signal Fsc. When the level is high (energization), the mode is switched to the b side, and a backward / steady feed speed setting signal Sr described later is output as the feed speed control setting signal Fsc. The steady feeding speed setting circuit FS outputs a predetermined steady feeding speed setting signal Fs. The reverse feed speed setting circuit FSR outputs a predetermined reverse feed speed setting signal Fsr.
[0024]
The arc start selection circuit SC indicated by a dotted line outputs an arc start selection signal Sc which is at a low level when the normal arc start control is selected and is at a high level when the retract arc start control is selected. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. As described above with reference to FIG. 3C, the short circuit determination circuit SD determines from the time when the occurrence of a short circuit is determined to the time when the delay time Td has elapsed after determining the occurrence of an arc based on the value of the voltage detection signal Vd. During this period, a short circuit determination signal Sd that is at a high level is output. The logical product circuit AND receives the arc start selection signal Sc and the short circuit determination signal Sd, and outputs a logical product signal And. The reverse / steady feed speed switching circuit SR switches to the a side when the logical product signal And is at the Low level, and outputs the above-mentioned steady feed speed setting signal Fs as the reverse / steady feed speed setting signal Sr. When it is at the High level, it switches to the b side and outputs the reverse feed speed setting signal Fsr as the reverse / steady feed speed setting signal Sr.
[0025]
Here, how the value of the feed speed control setting signal Fsc changes according to the set value of the arc start selection signal Sc will be summarized below.
(1) When the arc start selection signal Sc is at a low level (normal arc start control) (same as the operation of FIG. 2 described above)
Since the logical product signal And is always at the low level, the reverse / steady feed speed setting signal Sr is always the steady feed speed setting signal Fs. The feed speed control setting signal Fsc becomes the initial feed speed setting signal Fsi until the time when the energization determination signal Cd changes to the high level (energization) (time t2 in FIG. 2), and after that time the steady feed This is the speed setting signal Fs.
[0026]
(2) When the arc start selection signal Sc is at a high level (retract arc start control) (the same operation as in FIG. 3 described above).
The feed speed control setting signal Fsc becomes the initial feed speed setting signal Fsi until the time when the energization determination signal Cd changes to the high level (energization) (time t2 in FIG. 3). Subsequently, when the short circuit determination signal Sd changes to the high level (short circuit) (time t2 in FIG. 3), the logical product signal And changes to the high level, so that the feed speed control setting signal Fsc is the reverse feed speed setting signal. Fsr. Subsequently, when the short circuit determination signal Sd changes to the low level (time t4 in FIG. 3), the AND signal And changes to the low level, so that the feed speed control setting signal Fsc becomes the steady feed speed setting signal Fs. .
[0027]
The feed control circuit FC sends a feed control signal Fc for feeding the welding wire at a speed corresponding to the feed speed control setting signal Fsc when the welding start signal As is at a high level (start). Output to feed motor WM.
[0028]
The voltage setting circuit VS outputs a predetermined voltage setting signal Vs. The initial current setting circuit ISI outputs a predetermined initial current setting signal Isi. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vs and the voltage detection signal Vd and outputs a voltage error amplification signal Ev. By the feedback control of the voltage error amplification circuit EV, the external characteristic of the welding power source device becomes a constant voltage characteristic for supplying a steady welding current. The current error amplification circuit EI amplifies an error between the initial current setting signal Isi and the current detection signal Id and outputs a current error amplification signal Ei. By the feedback control of the current error amplifier circuit EI, the external characteristic becomes a constant current characteristic for supplying the initial current Is.
[0029]
The flip-flop circuit FF inputs the arc start selection signal Sc to the prohibit terminal, inputs the welding start signal As to the set (S) terminal, inputs the short circuit determination signal Sd to the reset (R) terminal, and switches the switching signal Ff. Is output. When the arc start selection signal Sc is at the low level (normal arc start control), the switching signal Ff is always at the low level. On the other hand, when the arc start selection signal Sc is at the high level (retract arc start control), the period from the time when the welding start signal As changes to the high level (start) to the time when the short circuit determination signal Sd changes to the low level (see FIG. 3 at time t1 to t4) becomes a high level. The external characteristic switching circuit SP outputs the voltage error amplification signal Ev as the error amplification signal Ea when the switching signal Ff is at the Low level, and outputs the current error amplification signal Ei as the error amplification signal Ea when the switching signal Ff is at the High level.
[0030]
When the arc start selection signal Sc is at a low level (normal arc start control), the voltage error amplification signal Ev is always selected to form a constant voltage characteristic. Therefore, as described above with reference to FIG. 2, when the welding wire comes into contact with the base material at time t <b> 2, a steady welding current is energized by the constant voltage characteristic corresponding to the voltage setting signal Vs. On the other hand, when the arc start selection signal Sc is at a high level (retract arc start control), the current error amplification signal Ei is selected during the period from time t1 to t4 in FIG. 3 to form a constant current characteristic. Therefore, during the period from time t1 to time t4 in FIG. 3 from when the welding start signal As is input to when the arc is generated and the delay time Td elapses, the constant current characteristic is applied to supply the initial current Is. In the subsequent period, a constant voltage characteristic is formed and a steady welding current is applied.
[0031]
When the welding start signal As is at a high level (start), the drive circuit DV outputs a drive signal Dv for forming a constant voltage characteristic or a constant current characteristic in accordance with the error amplification signal Ea.
[0032]
If the welding power supply apparatus described above is used, it is possible to select an arc start control method suitable for various welding conditions such as the type of welding wire and the feeding speed by simply switching the set value of the arc start selection signal Sc. .
[0033]
[Example 2]
The invention of Example 2 is an arc start control method in which the arc start selection signal described in the invention of Example 1 is set by switching an arc start selection switch provided in a welding power source device. Hereinafter, the invention of Example 2 will be described with reference to the drawings.
[0034]
In the welding power source apparatus for carrying out the invention of the second embodiment, the arc start selection circuit SC in the block diagram of FIG. 4 is configured as shown in FIG.
FIG. 5 is a block diagram of the arc start selection circuit SC of the second embodiment. The arc start selection switch SW is provided in the welding power source device, and is switched to the a side when selecting the normal arc start control, and is switched to the b side when selecting the retract arc start control. When the arc start selection switch SW is switched to the a side, a current flows through the resistor R and the voltage value V1 becomes approximately 0 [V]. Therefore, the arc start selection signal Sc, which is the output of the buffer circuit BUF, is low level. Become. On the other hand, when the arc start selection switch SW is switched to the b side, the voltage value V1 becomes approximately 5 [V], so that the arc start selection signal Sc becomes High level.
[0035]
As described above, the invention of the second embodiment can select an arc start control method suitable for various welding conditions only by switching the arc start selection switch SW.
[0036]
[Example 3]
In the invention of the third embodiment, the welding condition is set by a teach pendant, and in the robot arc welding performed using the welding power source device and the welding robot, the arc start selection signal described in the invention of the first embodiment is set to one of the above welding conditions. This is an arc start control method set by the teach pendant. Hereinafter, the invention of Example 3 will be described with reference to the drawings.
[0037]
FIG. 6 is a configuration diagram of a robot arc welding apparatus for carrying out the invention of the third embodiment. Teaching pendant TP presets welding conditions such as teaching of operation of manipulator RM, welding start signal As, voltage setting signal Vs, steady feed speed setting signal Fs, arc start selection signal Sc, and the like in robot controller RC. The robot controller RC outputs an operation control signal Mc for controlling the operation of the manipulator RM, a welding start signal As set by the teach pendant TP, a voltage setting signal Vs, a steady feeding speed setting signal Fs, and an arc start. A welding condition setting signal Ws including the selection signal Sc is output to the welding power source device PS. The welding power source PS sets the welding start signal As, the voltage setting signal Vs, the steady feed speed setting signal Fs and the arc start selection signal Sc in the block diagram of FIG. 4 described above by the above-described welding condition setting signal Ws. It has been changed to. The welding power supply device PS receives the welding condition setting signal Ws, outputs the welding voltage Vw and the welding current Iw, and outputs the feed control signal Fc to the feed motor WM. The welding wire 1 is fed through a welding torch 4 by a feeding motor WM, and an arc 3 is generated between the base metal 2 and welding is performed.
[0038]
As described above, in the invention of the third embodiment, the arc start selection signal Sc can be set by the teach pendant TP, and an arc start control method suitable for various welding conditions can be selected. In particular, the normal arc start control and the retract arc start control can be selected for each welding point by adding the set value of the arc start selection signal Sc to the work program of the welding robot.
[0039]
[Example 4]
The invention of the fourth embodiment is an arc start control method in which the arc start selection signal described in the invention of the first embodiment is set in response to the value of at least one of a welding wire selection signal or a feed speed setting signal. is there. Hereinafter, the invention of Example 4 will be described with reference to the drawings.
[0040]
In the welding power source apparatus for carrying out the invention of the fourth embodiment, the arc start selection circuit SC in the block diagram of FIG. 4 is configured as shown in FIG. 7 described below.
FIG. 7 is a block diagram of the arc start selection circuit SC of the fourth embodiment. The welding wire selection circuit MS outputs a welding wire selection signal Ms corresponding to the type of welding wire. For example, the welding wire selection signal Ms = 1 when the welding wire material is steel and the diameter is 1.2 [mm], and the welding wire selection is when the welding wire material is steel and the diameter is 1.0 [mm]. The signal Ms = 2, the welding wire selection signal Ms = 3 when the welding wire material is aluminum and the diameter is 1.2 [mm], the welding wire material is stainless steel and the diameter is 1.2 [mm]. The welding wire selection signal Ms = 4. The arc start selection circuit SC according to the fourth embodiment receives the welding wire selection signal Ms and the steady feeding speed setting signal Fs, and outputs an arc start selection signal Sc according to a predetermined rule in response to these values. . An example of this rule is shown in FIG. For example, when the welding wire selection signal Ms = 1 and the steady feed speed setting signal Fs ≦ 7 [m / min] (corresponding to 220 [A] in the welding current average value), the arc start selection signal Sc is at a high level ( When the normal feed speed setting signal Fs> 7 [m / min], the arc start selection signal Sc is at the low level (normal arc start control). When the welding wire selection signal Ms = 2 and the steady feed speed setting signal Fs ≦ 6 [m / min] (corresponding to 160 [A] in the welding current average value), the arc start selection signal Sc is at a high level ( When the normal feed speed setting signal Fs> 6 [m / min], the arc start selection signal Sc is at the low level (normal arc start control). Further, when the welding wire selection signal Ms = 3, the arc start selection signal Sc is at a high level (retract arc start control). The above rule is an example. For example, when the welding wire selection signal Ms = 1, the arc start selection signal Sc can be determined as the low level (normal arc start control) according to the required welding quality level. When the welding wire selection signal Ms = 4, the arc start selection signal Sc can be set to the high level or the low level according to the value of the steady feed speed setting signal Fs. Furthermore, the circuit block of FIG. 7 may be provided inside the welding power source apparatus, or may be provided inside the robot control apparatus RC of FIG. 6 described above.
[0041]
As described above, in the invention of the fourth embodiment, the optimum arc start control method is automatically selected according to the type of the welding wire and the feeding speed.
[0042]
[Example 5]
The invention of Example 5 is an arc start control method in which the arc start selection signal described in the invention of Example 1 is set in response to the welding stop time from the previous welding end time to the current welding start time. . Hereinafter, the invention of Example 5 will be described with reference to the drawings.
[0043]
In the welding power source apparatus for carrying out the invention of the fifth embodiment, the arc start selection circuit SC in the block diagram of FIG. 4 described above is configured as shown in FIG.
FIG. 8 is a block diagram of the arc start selection circuit SC of the fifth embodiment. The welding stop time measurement timer circuit TM outputs a timer signal Tm having a value proportional to the length of time that the energization determination signal Cd is at the low level (non-energization). The comparison circuit CM compares the value of the timer signal Tm with a predetermined reference value Ts, and outputs a low level (normal arc start control) arc start selection signal Sc when Tm ≦ Ts, and Tm> At Ts, an arc start selection signal Sc of High level (retract arc start control) is output.
[0044]
As described above, in the invention of Example 5, the optimum arc start control method is automatically selected according to the value of the welding stop time (timer signal Tm) from the previous welding end time to the current welding start time. Can do. The reason for the above is that when the welding stop time is short, the tip of the welding wire is heated by the previous welding and remains at a high temperature, so that the next arc start will be good even with normal arc start control. is there. Further, the above-described invention of the fifth embodiment can be used in combination with the inventions of the first to fourth embodiments.
[0045]
【The invention's effect】
In the arc start control method of the present invention, the arc start selection signal can be set to an appropriate value in response to the welding stop time. As a result, the arc start performance is good when the welding stop time is short and the tip of the welding wire is still hot, so normal arc start control is performed to improve production efficiency and extend the life of consumable parts, etc. When the welding stop time becomes long and the tip of the welding wire becomes low in temperature, retract arc start control can be performed to improve arc start performance.
[Brief description of the drawings]
FIG. 1 is a block diagram of a conventional consumable electrode gas shield arc welding apparatus.
FIG. 2 is a timing chart of normal arc start control of prior art 1
FIG. 3 is a timing chart of retract arc start control according to prior art 2;
FIG. 4 is a block diagram of a welding power source apparatus according to the first embodiment.
FIG. 5 is a block diagram of an arc start selection circuit according to a second embodiment.
FIG. 6 is a configuration diagram of a welding apparatus according to a third embodiment.
FIG. 7 is a block diagram of an arc start selection circuit according to a fourth embodiment.
FIG. 8 is a block diagram of an arc start selection circuit according to a fifth embodiment.
[Explanation of symbols]
1 Welding wire
2 Base material
3 Arc
3a initial arc
3b Steady arc
4 Welding torch
4a Contact chip
5 Feeding roll
AND AND circuit
And AND signal
AS welding start circuit
As welding start signal
BUF buffer circuit
CD energization discrimination circuit
Cd Energization discrimination signal
CM comparison circuit
DV drive circuit
Dv drive signal
Ea Error amplification signal
EI current error amplifier circuit
Ei Current error amplification signal
EV voltage error amplifier circuit
Ev Voltage error amplification signal
FC feed control circuit
Fc feed control signal
FF flip-flop circuit
Ff switching signal
FS steady feed speed setting circuit
Fs Steady feed speed setting signal
Fsc Feeding speed control setting signal
FSI initial feed speed setting circuit
Fsi Initial feed speed setting signal
FSR reverse feed speed setting circuit
Fsr Reverse feed speed setting signal
ID current detection circuit
Id Current detection signal
INV output control circuit
Is Initial current
ISI initial current setting circuit
Isi initial current setting signal
Iw welding current
Lw Distance between wire tip and base material
MS welding wire selection circuit
Ms Welding wire selection signal
PS welding power supply
R resistor
RC robot controller
RM manipulator
SC arc start selection circuit
Sc Arc start selection signal
SD short-circuit detection circuit
Sd Short circuit detection signal
SF Feeding speed switching circuit
SP external characteristic switching circuit
SR reverse / steady feed speed switching circuit
Sr Reverse / steady feed speed setting signal
SW Arc start selection switch
Td delay time
TM Welding stop time measurement timer circuit
Tm Timer signal
TP teach pendant
Ts (welding stop time) reference value
V1 voltage value
VD voltage detection circuit
Vd Voltage detection signal
VS voltage setting circuit
Vs Voltage setting signal
Vw welding voltage
WM feed motor
Ws Welding condition setting signal

Claims (1)

When the welding start signal is input, the welding wire is fed forward to the base metal. When the welding wire comes into contact with the base metal, an initial current of a small current value is supplied and the welding wire is fed backward from the base material. Retract arc start control in which the welding wire is separated from the base material by feeding and the welding wire is fed forward again after the initial arc is generated, and a steady welding current is applied to shift to the steady arc, and the welding start signal Is provided with a normal arc start control that feeds a welding wire forward to the base metal when the is input, and generates a steady arc by energizing a steady welding current when the welding wire contacts or approaches the base material,
A consumable electrode gas shield that switches between the retract arc start control and the normal arc start control by an arc start selection signal set in response to a welding stop time from the end of the previous welding to the start of the current welding. Arc start control method for arc welding.

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