JP3104494B2 - Control device for arc welding robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller for performing arc welding.

[0002]

2. Description of the Related Art Conventionally, in an arc welding system using a robot, if current cannot be detected at the time of arc start and arc welding cannot be performed, the arc start operation is repeated until a preset number of times is reached. However, if the arc start is repeatedly performed in a state where the consumable electrode (hereinafter referred to as a wire) is fused to the welding tip, there is a risk of damaging the wire feeding path and the welding power source.

[0003]

SUMMARY OF THE INVENTION In order to avoid such a danger in the prior art, the present invention is to prevent a current from being detected due to an arc start error at the time of an arc start, and a wire feed motor at the time of the arc start error. If the torque value of the wire feed motor deviates far from the torque value of the wire feed motor performing the normal wire feed, and the torque value of the wire feed motor is When the torque value of the wire feeding motor that performs the wire feeding is far out of alignment, it is determined that the wire is fused to the chip, the welding operation is immediately stopped, and then the robot is temporarily stopped. It is an object to provide a robot control device having means.

[0004]

In order to achieve the above object, a welding robot control apparatus according to the present invention provides a method for controlling arc welding.
Sometimes, a DC voltage is applied between the wire and the welding base metal,
Stick status can be detected by the presence or absence of current based on pressure
Circuit, and the consumable electrode sticks to the workpiece
Check that there is no
For bots, feed consumable electrodes during arc welding
The wire feed module attached to the welding wire feeder
A circuit that detects the torque value during actual wire feeding of the
The wearable electrode is fused to the chip and the feed motor feeds the wire.
To the torque value when the motor is running idle and slipping
A reference signal circuit for outputting a corresponding value;
Two torque values during wire feeding are used as input signals and wire feeding
The torque value of the feed motor during the actual wire feeding is
The feed motor is slipping due to idling without feeding the wire
When the value exceeds the reference signal value corresponding to the torque value in the state
And a comparison circuit that outputs a signal at the time of arc start.
Current cannot be detected due to arc start mistake at
When the signal from the circuit is being output, feed the wire back
Even when the signal is output from the comparison circuit, the welding wire
Screen is determined to be in a state where the
After stopping the welding operation
Having means for temporarily stopping the robot body.
You.

[0005]

As described above, according to the present invention, a wire feeding motor is provided.
Armature current detector, and the output waveform of the detector is
Shaped and pulsed motor armature current with current detector
Detected, integrated and smoothed comparison signal and wire are weld tips
90 when the wire feed motor is slipping
% Reference signal and the two signals
The armature of the wire feed motor during the actual wire feed
The comparison signal value obtained by detecting and processing the current is different from the reference signal value.
Has a comparison circuit that outputs an output signal when the
I do. Arc start mistake at arc start and current
If it cannot be detected and the output of the comparator is ON,
Next, what is the output of the comparator even if the wire is fed back?
If it is ON, check that the welding wire is
Is determined to be fused to the tip
Output the alarm and stop the welding operation immediately.
With this configuration , if it is determined that an arc start error has occurred due to the wire being fused, the welding operation is immediately stopped and the robot is temporarily stopped, and the state of the fused tip is displayed on the monitor screen. Then, an alarm output can be issued to the outside. This eliminates the risk of damaging the wire feed path and welding power source because the arc start operation is not repeated with the wire fused to the tip. It can be done quickly, and the operating rate of the robot, and eventually the welding line built into the robot, can be increased compared to the conventional method.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. 1 is a configuration diagram of a welding robot system of the present invention, FIG. 2 is a diagram of a wire feeding device, FIG. 3 is a graph showing a relationship between a torque generated by the wire feeding motor and an armature current of the wire feeding motor, FIG. 4 is a diagram of an algorithm for judging a chip fusion state, and FIG. 5 is a circuit for detecting a state in which the wire feeding motor is not able to perform normal feeding and reverse feeding of the wire and is slipping.

In the welding robot system shown in FIG. 1, when welding is started, a welding wire is fed by the wire feeder shown in FIG. 2 in proportion to a welding current command value. Here, FIG.
The wire feed motor in the wire feeder is driven by a wire feed motor governor circuit (not shown). The governor circuit detects a motor induced voltage proportional to the wire feed motor rotation speed and feeds at a fixed period. Control is performed by comparing with the motor rotation command voltage. According to the comparison result, when the actual rotation speed of the wire feed motor (wire feed motor induced voltage value) is smaller than the rotation speed corresponding to the wire feed motor rotation command voltage value, a signal is transmitted to the oscillation circuit to promote oscillation. The thyristor (gate) circuit controls the thyristor in a direction in which the firing angle (phase) of the thyristor is widened and the rotation of the wire feed motor is accelerated. Conversely, when the actual wire feed motor rotation speed (wire feed motor induced voltage value) is greater than the wire feed motor rotation command voltage value, a signal is transmitted to the oscillation circuit to suppress oscillation, and the firing angle of the thyristor ( Phase) to reduce the rotation of the feed motor. Since the wire feed motor governor circuit feeds back the feed voltage of the wire feed motor and performs comparative control at a fixed cycle as described above, a highly accurate and stable wire feed performance is realized, and the welding wire feed speed is increased. Is maintained at a constant speed to stabilize the welding state. In the wire feed motor shown in FIG. 2, the torque generated by the motor is directly proportional to the armature current flowing through the motor, similarly to a general motor, and this proportional constant is called a torque constant. That is, the generated torque is T, the armature current of the motor is _Io ,
Assuming that the torque constant is K _t , T [kg f · cm] = K _t [kg f · cm / A] × I _o [A r
ms]. This relationship is shown in FIG. In the wire feeding device shown in FIG. 2, a gear having a reduction ratio of 1/25 is interposed between the wire feeding motor and the feed roller in the wire feeding device of FIG. 2 which actually feeds the welding wire. Therefore, if the transmission loss and the like are ignored, a torque 25 times the generated torque of the motor is transmitted to the feed roller and the wire is fed.

Next, a description will be given mainly with reference to FIG. In FIG. 5, the current detector of the torque detection unit of the feed motor receives a current flowing through the wire feed motor as an input and outputs a voltage proportional to the current value. The contact point CR in FIG. 5 indicates that the current detector outputs a positive voltage regardless of whether the wire feed motor, which is the DC motor in the wire feed device in FIG. The circuit is switched so that the direction of the armature current of the wire feed motor matches the direction of the current. The switching contact CR enables the torque detection circuit of the wire feed motor to be used for the normal rotation and the reverse rotation of the wire feed motor.
The processing can be performed only by the forward rotation torque detection circuit without preparing two circuits.

The current detector of the torque detector of the wire feed motor outputs a voltage proportional to the wire feed motor armature current flowing through the detector. The output voltage passes through a filter (integration) circuit of the torque detecting unit, and is shaped and smoothed into a voltage value proportional to the torque value of the wire feed motor. Here, the final output voltage of the torque detection unit of the above-described feed motor was measured while the wire was fixed and the wire feed motor was not able to feed the wire and was in a state of slipping. The 90% value is set by the variable resistor of the reference signal section so as to be the reference voltage of the reference signal section. Where 90
The% value is a value obtained experimentally, and is not detected by torque fluctuation in a normal wire feeding state of the wire feeding motor (normal judgment). The level is always detected in the wire feeding state in which the feed roller cannot feed the wire and slips without slipping. The comparator outputs an output signal and turns on the photocoupler of the signal processing unit when the output voltage value of the torque detection unit of the feed motor becomes larger than the reference voltage value. The signal processing unit and the analog circuit units such as the torque detection unit and the reference signal unit of the feed motor are electrically insulated by a photocoupler. In the signal processing section, when the photocoupler is turned on, a trigger signal is input to the subsequent latch circuit, the output Q of the latch circuit is turned on, and
It is transmitted to PU. When the arc start fails and the welding current cannot be detected due to an arc start at the time of the arc start and the latch output Q is present, the CPU sends a reset signal of the Q output to the latch circuit to turn off the latch output and operate the switching contact CR. After switching the circuit in which the armature current of the wire feed motor flows through the current detector, the wire is reversely fed for a time Δt, and the state of the latch output Q is checked again.
In the case of N, it is determined that the welding wire is fused to the chip, and FIG.
"Tip fusion" is displayed on the LCD screen of the teach pendant, and an alarm is output to the outside to stop the welding operation, and then the robot is temporarily stopped. This flow is shown in the algorithm of FIG. Normally, when an arc start miss occurs, an arc start operation is attempted until the maximum number of repetitions is reached. When the torque value of the wire feed motor is much larger than the normal torque value when the wire feed motor feeds the wire forward or backward in this algorithm, in other words, the reference of FIG. When the signal voltage is equal to or higher than the reference voltage value of the signal circuit, it is determined that the welding wire is fused to the chip. Here, the feed amount of the welding wire is proportional to the welding current command and the wire feed motor energizing time Δt.
In the experiment, the wire feed motor energizing time Δt was controlled with the protrusion length of the welding wire of 15 mm, and the wire reverse feed amount was 5 mm. At the time of an arc start mistake, the welding current command value is continuously output, but the command value is maintained as it is, and the relationship between the welding current command value obtained experimentally and the wire feeding motor energizing time Δt is determined. The wire feed motor feed amount is controlled by controlling only the wire feed motor energizing time Δt.

[0010]

As is apparent from the above description, according to the present invention, as shown in the circuit of FIG. 5, the wire feed motor shown in FIG. 9
A 0% value is generated as a reference signal, and the torque value of the wire feed motor obtained by shaping the armature current of the wire feed motor with a circuit using a current detector and the like as a reference input of the comparator is compared with the comparator. By comparing and judging them as input and processing according to the algorithm of FIG. 4, the fusion state of the welding wire to the chip can be judged. Therefore, it is possible to avoid the risk of damaging the wire feeding path and the welding power source without repeating the arc start with the welding wire fused to the chip. Further, since the cause of the arc start mistake is clear, the recovery work can be immediately started, and the operation rate of the robot or the welding line incorporating the robot can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a welding robot system according to the present invention.

FIG. 2 is a configuration diagram of a wire feeding device.

FIG. 3 is a diagram showing a relationship between a torque generated by a feed motor and an armature current;

FIG. 4 is a diagram showing an algorithm for determining a fusion state of a welding wire to a chip at the time of arc start.

FIG. 5 is a circuit diagram of detection of a wire feeding disabled state of the feed motor and processing of the disabled state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Teach pendant (monitor) 2 Welding wire 3 Welding power supply 4 Robot main body 5 Wire feeder 6 Wire reel stand 7 Wire feed motor 8 Feed roller 9 Welding wire

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 9/12 B25J 13/00

Claims (1)

(57) [Claims] 1. A circuit for applying a DC voltage between a wire and a welding base material at the end of arc welding and detecting a stick state based on the presence or absence of a current based on the DC voltage. In the welding robot that moves to the next welding process after confirming that it is not, the torque at the time of the actual wire feeding of the wire feeding motor attached to the welding wire feeding device that feeds the consumable electrode during arc welding And a reference signal for outputting a value corresponding to the torque value when the consumable electrode is fused to the chip and the feed motor cannot feed the wire and is idle and slipping. Circuit, and the torque value of the wire feed motor at the time of wire feed is used as an input signal, and the torque value of the wire feed motor at the time of actual wire feed is such that the wire feed motor cannot feed the wire. Idle rotation And a comparator circuit for outputting a signal when a corresponding reference signal value or the torque value at the time Tsu and has state, the arc start mistakes during arc starting
The current cannot be detected and the signal from the comparison circuit is output.
Signal is output from the comparison circuit even if the wire is
An arc welding robot having means for judging that the welding wire is fused to the tip when the force is applied, notifying the outside with a screen display and an alarm output, and stopping the welding operation and then temporarily stopping the robot body. Control device.