JPH07116843A - Controller for arc welding robot - Google Patents

Abstract

PURPOSE:To surely determine a fused bonded state on a tip of a welding wire and to prevent damage of a welding power source. CONSTITUTION:When a torque value of a wire feed motor 7 is far larger than a normal feed value at the time of missing arc start, the welding wire is fed reversely by the time DELTA(t) by the wire feed motor 7 by the specified length and the torque value of the motor 7 at that time is far larger than the normal feed value, it is determined that the welding wire 9 is fused bonded on the tip and welding operation is stopped.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an arc welding system using a robot, if the current cannot be detected at the time of arc start and the arc welding cannot be performed, the arc start operation is repeated until a preset number of times. However, if arc start is repeatedly performed in a state where a 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 The present invention, in order to avoid such a risk as in the prior art, cannot detect the current due to an arc start miss at the arc start, and the wire feed motor at the arc start miss. The torque value of the wire feed motor is normal when the torque value of the wire feed motor deviates far from the torque value of the wire feed motor that is performing normal wire feed and when the wire is fed backward. If the wire feed motor torque is far out of line, it is determined that the wire is fused to the tip and the welding operation is immediately stopped and then the robot is temporarily stopped. An object of the present invention is to provide a robot control device having means.

[0004]

In order to achieve the above object, the welding robot controller of the present invention comprises a detector of the armature current of the wire feeding motor, and shapes the output waveform of the detector. A comparison signal obtained by detecting the pulsed armature current of the motor with a current detector, integrating and smoothing it, and the wire being fused to the welding tip and the wire feeding motor slipping
A reference signal having a value of 0% is used as an input signal for these two signals, and the above-mentioned comparison signal value obtained by detecting and processing the armature current of the wire feeding motor during actual wire feeding is higher than the reference signal value. It has a comparison circuit that outputs an output signal when it becomes large. If the current cannot be detected due to a missed arc start at the time of arc start, and the output of the comparator is ON, the output of the comparator is checked even if the wire is fed backward, If it is ON, it is determined that the welding wire is fused to the tip, the tip fusion is displayed, an alarm output is output to the outside, and the welding operation is immediately stopped.

[0005]

According to the present invention, when it is determined that an arc start miss occurs because the wire is fused to the tip, the welding operation is immediately stopped, and the robot is temporarily stopped so that the tip is fused. It can be displayed on the monitor screen and output an alarm to the outside. This eliminates the risk of damaging the wire feed route and welding power source because the wire will not repeat the arc start operation while the tip remains fused, and the cause of the arc start mistake is clear, so recovery work can be performed. It can be done quickly and can increase the operating rate of the robot and, by extension, the welding line built into the robot.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 torque generated by a wire feeding motor and armature current of the wire feeding motor, FIG. 4 is a diagram of an algorithm for determining the chip fusion state, and FIG. 5 is a circuit for detecting a state in which the wire feeding motor cannot perform forward and backward feeding of the wire and slips.

In the welding robot system of FIG. 1, when welding is started, the welding wire is fed by the wire feeding device of FIG. 2 in proportion to the welding current command value. Here, FIG.
The wire feeding motor in the wire feeding device is driven by a wire feeding motor governor circuit (not shown), but the governor circuit detects the motor induced voltage proportional to the wire feeding motor rotation speed and feeds the motor at a constant cycle. Control by comparing with the motor rotation command voltage. From this comparison result, when the wire feed motor actual rotation speed (wire feed motor induced voltage value) is smaller than the rotation speed equivalent 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 direction in which the firing angle (phase) of the thyristor is widened to accelerate the rotation of the wire feeding motor. Conversely, when the wire feed motor actual rotation speed (wire feed motor induced voltage value) is larger 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 ( The phase is narrowed to control the rotation of the feed motor. As described above, the wire feeding motor governor circuit feeds back the wire feeding motor induced voltage and performs comparative control at a fixed cycle, so it achieves highly accurate and stable wire feeding performance and the welding wire feeding speed. Is maintained at a constant speed to stabilize the welding state. In the wire feeding motor shown in FIG. 2, the torque generated by the motor is directly proportional to the armature current flowing through the motor, like a general motor, and this proportional constant is called a torque constant. That is, the generated torque is T, the motor armature current is I _o ,
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 transmission loss and the like are ignored, 25 times the torque generated by the motor is transmitted to the feed roller and the wire is fed.

Next, the description will be centered on FIG. In FIG. 5, the current detector of the torque detection unit of the feed motor receives the 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 is a DC motor in the wire feeding device in FIG. 2, and the wire feed motor penetrates the current detector that outputs a positive voltage regardless of whether the wire feed motor is forward feeding or reverse feeding. It is for switching the circuit so that the armature current direction of the wire feeding motor coincides with the current direction. With this switching contact CR, the torque detection circuit of the wire feeding motor can be used for two rotations, one for forward rotation and the other for reverse rotation.
It is possible to process only the torque detection circuit for forward rotation without preparing two circuits.

The current detector of the torque detector of the wire feed motor outputs a voltage proportional to the current of the wire feed motor armature flowing through the detector. The output voltage passes through the filter (integration) circuit of the same torque detection unit, and the waveform is shaped and smoothed to become a voltage value proportional to the torque value of the wire feeding motor. Here, the wire is fixed and the wire feeding motor cannot feed the wire and slips in a dry state, and the final output voltage of the torque detecting unit of the feeding motor is measured. The 90% value is set by the variable resistor of the reference signal unit so as to become the reference voltage of the reference signal unit. Where 90
The% value is an experimentally obtained value, and it cannot be detected by the torque fluctuation of the wire feeding motor in the normal wire feeding state (judgment of normality), and the wire cannot be fed. This is a level that is always detected when the feed roller is in a wire feeding state in which it cannot slip the wire and slips. 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 section and the analog circuit section such as the torque detection section of the feed motor and the reference signal section are electrically insulated by a photo coupler. In the signal processing section, when the photo coupler is turned on, the trigger signal is input to the latch circuit in the subsequent stage and the output Q of the latch circuit is turned on and C
It is transmitted to PU. When the CPU does not detect the welding current due to an arc start error at the arc start and the latch output Q is present, the CPU sends a reset signal of 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 feeding motor flows through the current detector, the wire is fed backward for a time of Δt and the state of the latch output Q is checked again to confirm that the output is O.
In the case of N, it is determined that the welding wire is fused to the tip,
On the LCD screen of the teach pendant of “Welding abnormal tip fusion” is displayed and an alarm output is output to the outside to stop the welding operation, and then the robot is suspended. This flow is shown in the algorithm of FIG. Normally, when an arc start miss occurs, the arc start operation is tried until the maximum number of repetitions is reached. In this algorithm, when the wire feeding motor feeds the wire forward and backward as well, when the torque value of the wire feeding motor is much larger than the torque value at the normal time, in other words, the reference of FIG. When the voltage exceeds the reference voltage value of the signal circuit, it is determined that the welding wire is fused to the tip. Here, the feeding amount of the welding wire is proportional to the welding current command and the wire feeding motor energization time Δt.
In the experiment, the wire feed motor energization time Δt was controlled with the welding wire protruding length of 15 mm and the wire reverse feed amount was set to 5 mm. When the arc start error occurs, 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 in the experiment and the wire feed motor energization time Δt is shown. The wire reverse feed amount is controlled by controlling only the wire feed motor energization 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 feeding motor shown in FIG. 9
The 0% value is created as a reference signal and the reference value of the comparator is used as the reference input. The torque value of the wire feed motor is calculated by waveform shaping the armature current of the wire feed motor by a circuit using a current detector. The fusion state of the welding wire to the tip can be determined by comparing the two as inputs and processing them according to the algorithm of FIG. Therefore, it is possible to avoid the risk of damaging the wire feeding path and the welding power source without repeating the arc start while the welding wire is fused to the tip. In addition, since the cause of the arc start mistake is clear, the recovery work can be immediately started to increase the operation rate of the robot or the welding line incorporating the robot.

[Brief description of 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 welding state of a welding wire on a tip at the time of arc start.

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

[Description of symbols] 1 teach pendant (monitor) 2 welding wire 3 welding power source 4 robot body 5 wire feeder 6 wire reel stand 7 wire feeding motor 8 feed roller 9 welding wire

[Procedure amendment]

[Submission date] December 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

Claims (1)

[Claims] 1. A circuit for applying a DC voltage between a wire and a welding base metal at the end of arc welding, and detecting a stick state by the presence or absence of a current based on the DC voltage, wherein the consumable electrode sticks to a workpiece. In the welding robot that moves to the next welding process work after confirming that there is no welding, the torque of the wire feeding motor of the wire feeding motor attached to the welding wire feeding device that feeds the consumable electrode during arc welding A circuit that detects the value and a reference signal that outputs a value corresponding to the torque value when the consumable electrode is fused to the chip and the feeding motor cannot idle the wire and idles and slides. The circuit and the torque value at the time of wire feeding of the feeding motor are input signals, and the torque value at the time of actual wire feeding of the wire feeding motor is such that the wire feeding motor cannot feed the wire. Spin around The welding wire feeding device is equipped with a comparison circuit that outputs a signal when it becomes equal to or greater than the reference signal value corresponding to the torque value in the slipping state. When the comparison circuit is outputting an output signal, it is determined that the consumable electrode is fused to the welding tip, and an external screen display and an alarm output are provided to notify the robot body after the welding operation is stopped. A control device for a welding robot having means for temporarily stopping.