JPS5886983A - Detection of welding point for automatic welding robot - Google Patents

Abstract

PURPOSE:To eliminate the need for electric power sources for detection and selecting switches and to obtain good detecting sensitivity by making combination use of an electric power source for welding for detecting of weld points as well and controlling the output current of the power source for welding to at least the current at which a welding wire does not melt. CONSTITUTION:A circuit 10 outputs the data for moving a torch 14 downward in a Z-axis direction to a robot body, and outputs a current command for detection of welding points and a stop command signal for wire feeding to a circuit 11 via a circuit 15. Then, the robot body controls the axis for the downward movement of the torch and the circuit 11 controls an electric power source 12 so as to make the voltage applying to the wire 17 high and the current flowing to the wire 17 small. This current value is set within the range where the wire is not melted. The circuit 11 further stops the output of the wire feed command signal to a motor 16 and maintains the wire length at the preceding end of the torch at a prescribed length. If there is contact or discharge between the wire and a base metal 19 on controlling of the torch axis, the downward movement of the torch is stopped by the detection of the change in the current value of a detector 13, and the circuit 10 takes the data on the torch position therein. The similar operations are performed with respect to an X-axis and the position data is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a 1s contact point of an automatic welding robot for detecting a welding point of a workpiece.

Generally, when automatic welding is performed using an automatic welding robot II, it is necessary to import the position data of the welding point on the welding line in advance in order to control the torch by following the S tangent of the workpiece (base metal). . Conventionally, when capturing this position data, the torch acts as its own sensor, automatically! There is a 5K welding point detection method that detects the contact point.

In this detection method, as shown in FIG.
It is used by switching depending on the situation. When detecting a welding point using this method, first, a switching signal is output from the control box 5 to the changeover switch 3, and the movable contact piece 3a of the changeover switch 3 is switched from the welding power source I side to the detection power source 2 side.

Note that the detection power source 2 is a high voltage power source for discharging, and is designed to allow only a small current to flow.

Next, the control box 5 lowers the torch 6 in two axial directions, and when the current sensor 4 detects the point at which a spark flies between the welding wire 7 at the tip of the torch and the base metal 8, the control box 5 lowers the torch 6 in two axial directions. When the torch 6 is stopped, the position data of the torch 6 on two axes is taken in.

Similarly, position data of the torch 6 on the X-axis is taken in from the time when a spark flies between the welding wire 7 and the base metal 9.

In this way, the aiming position data of the torch 6 is captured in advance, and the torch 6 is scanned based on this position data. It is necessary to have a power source. 3. Also, a changeover switch is required to select and use the superposition for welding and the power source for detection. Because a large current flows through the changeover switch, an inexpensive one (with a maximum capacity of 500 A) must be used, and it also causes a decrease in 1s11 performance. Instead of alternately turning on and off the power switch with the power supply, it is possible to consider a method that does not use the changeover switch, but in this case, there will be restrictions on the output voltage of the detection power supply (the output voltage of the detection power supply will be higher). However, if this voltage is high, it does not adversely affect the internal circuit elements of the welding power source), so there is a problem that the detection sensitivity decreases.

The present invention has been made in view of the above-mentioned circumstances, and is designed for use with f# protrusion, which does not include a detection power supply and a changeover switch, improves reliability, reduces costs, and provides good detection sensitivity. The purpose of this invention is to provide a method for detecting robot welding points.

According to this invention, only one welding power source is required! It is also used for II contact detection, and when detecting a welding point, the output current of the welding power source is controlled so that at least the welding wire does not melt.

The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of the welding point detection method for a welding robot according to the present invention, and shows a welding point. Pot control circuit lO
1 control circuit 11, welding paper 12, and current detector 13. The welding robot control circuit 10 inputs and outputs data necessary for axis control of the torch 14 to and from the robot body (not shown), and also inputs and outputs data necessary for controlling the axis of the torch 14 to and from the robot body (not shown), as well as an output circuit 15 and lines a, b, and e.

A voltage command signal, a current command signal, an arc-on command signal, and a wire feed stop command signal are outputted to the control circuit 11 via d during welding and when #1 contact is detected, respectively.

The control circuit 11 controls the output voltage and output current of the "'C welding power source 12 based on these command signals, and also controls the wire feed motor 16, so as to appropriately feed the welding wire 17 via a line. A wire feed command signal is applied to the motor 16 via line f.

The wire feed motor 16 controls the rotation of the wire reel 18, and feeds the welding wire 17 to the tip of the torch 14 at a predetermined speed.

The current detector 13 detects a change in the current value caused by contact or discharge between the welding wire 17 and the base metal 19, and sends a signal indicating the presence or absence of this current value change to the welding robot control @ path via the input enclosure 20. Output to 1G.

Next, the operation of each of the above circuits when detecting a welding point will be explained.

The welding robot control circuit 10 outputs data for lowering the torch 17 in two axial directions to the robot body, and also outputs a voltage command signal for detecting 1llll contacts, a current command No. 18, and a wire feed stop command signal. Output circuit 1
5 to the control circuit 11. The robot body performs axis control to lower the torch 1 based on input data. Further, the control circuit 11 controls the voltage of the welding power source 12 so that the voltage applied to the welding wire 17 becomes a high voltage according to the voltage command signal, and the current flowing through the welding wire 17 becomes a small current according to the current command signal. The output current of #I connection power supply 12 is controlled so that Note that this current value is set within a range that does not melt the welding wire 17. Further, the control circuit 11 stops outputting the wire feeding command signal to the wire feeding motor 16 in response to the wire feeding stop command signal. As a result, the wire at the tip of the torch is held at a predetermined length.

Welding wire 1 with the torch axis control of the robot body
7 comes into contact with the base metal 19 or when there is a discharge between the welding wire 17 and the base metal 19, the current detector detects a change in the flowing current value and sends a signal indicating the current value change to the input circuit 20. It is output to the welding robot control (b) path 10 via the welding robot control path 10.

When a signal is applied from the input circuit 20, the welding robot control circuit 10 takes in the current position data of the torch 14 (lI*wire tip) from the robot body and stops the torch 14 from descending.

Subsequently, the welding robot control circuit 1G raises the torch 14 to a predetermined height, and then outputs data to the robot body to move the torch 14 to the left in the X-axis direction.

Thereby, the welding robot control circuit IO can take in the position data of the tip of the #I welding wire on the base material 21 in the same manner as described above.

The welding robot control circuit IO controls the base material 19 taken in above.
Based on the position data on the top and the position data on the base material 21 [, base material 19. Pupil data corresponding to the welding point on the welding line formed by 21 can be calculated.

During welding, the welding robot control circuit IO positions the welding wire tip at the welding point based on the calculated position data, outputs a voltage command signal and a current command signal for welding,
After the welding wire tip is positioned at the welding point, an arc-on command signal is output and a wire feed stop command signal is released.

In the above embodiments, the case where the angle between the base material 19 and t21 is a right angle has been described, but the present invention can be applied even when this angle is not a right angle. In this case, two different position data on the base material 19 and on the base material 21 (total of four position data) should be taken in, and the position data corresponding to the f#r contact point should be calculated based on these position data. Bye.

As explained above, according to the present invention, it is possible to detect welding spots using only a welding power source without having a particular power source for detection.
Moreover, good detection sensitivity can be obtained.

Furthermore, since no changeover switch is used, reliability can be expected to improve.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional weld point detection method, and FIG. 2 is a block diagram showing an embodiment of the weld point detection method for an automatic welding robot according to the present invention. DESCRIPTION OF SYMBOLS 10...Welding robot control circuit, 11...Control circuit, 12...Welding power source, 13...Paper flow detector, 14
...Torch, 16...Wire feeding motor, 17...
・Welding wire, 18°°. Wire reel, 1'J, 21... Base material.

Claims (1)

[Claims] A welding power source current control means for controlling the output current of the welding power source is provided on the output side of the welding power source, and when a welding point is detected, the welding power source current control means controls the output current of the welding power source at least as far as the welding wire. The torch was controlled to a current that would not cause melting, the torch was moved in a predetermined direction, the position of contact or proximity between the wire tip and the base metal was detected from the change in the output current, and the welding point was detected based on the detected position. Automatic welding robot welding point detection method