JPH0327876A - Controller for arc welding robot - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an arc start miss by giving single harmonic motion with minute amplitude to a torch at a welding starting point, returning the torch to the welding starting point when receiving an arc start confirmation signal from a welding machine and moving it toward a next teaching point. CONSTITUTION:When the torch 5 attains an arc starting point P1, an arc start command is transmitted from a controller to the welding machine and the torch 5 once stops at the above-mentioned starting point P1. The torch 5 then starts weaving between P0 separated by the minute distance (l) and the starting point P1 in the surface to cross almost orthogonally to a weld line 10. When the arc start is confirmed by the welding machine, the torch 5 attains the starting point P1. When the attainment is confirmed, the torch 5 stops weaving operation and starts to travel toward a next teaching point on the weld line. T he arc can be surely started at the welding starting point by destroying a surface insulating coating film of a wire or base metal and reducing contact resistance by the abovementioned weaving.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an arc welding robot, and particularly to a robot control device suitable for preventing arc start errors. [Conventional technology] In recent years, robotization of arc welding processes has progressed rapidly, and it is now common for robots to weld complex weld lines that could only be done manually at multiple locations per work program. It has become a target. Conventionally, signals are exchanged between the robot control device 1 that controls the robot and the welding machine 2, as shown in FIGS. 5 and 6. When the point is reached, the arc start signal 3 is issued from the control device 1 to the welding machine 2, and when the arc start confirmation signal 4 is input from the welding machine 2 to the control device 1, the torch 5 moves to the next teaching point. It was starting to run towards the station. [Problem to be solved by the invention] As mentioned above, in robot equipment that performs welding at a large number of locations, the most serious problem in line management at present is the so-called arc start error, in which the arc does not start at the welding start point. The equipment will stop due to this occurrence. According to actual results, approximately 60% to 70 of the equipment stoppages occur on arc welding lines with robot equipment.
% is due to this arc start error. When this arc start error occurs, it takes about 2 to 6 minutes for maintenance personnel to perform prescribed maintenance and restart the line, resulting in a problem that the operating rate of the entire line decreases.

There are three main reasons why such arc start errors occur: (1) An oxide film is formed at the tip of the wire, so even if the wire contacts the base metal and voltage is applied, no current flows. (2) The surface quality of the base material is poor and the resistance of the contact area is similarly high, so no current flows. This is especially true when trying to start an arc from a part of the base metal surface where a weld bead has already been formed, and this may be caused by silicon-based slab insulation that remains on the bead. many.

(3) The frictional resistance inside the welding torch, especially inside the tip, becomes large when the wire runs, and the wire is not fed even if the welding machine starts the welding sequence and the wire feeding motor rotates. The rate at which the above three causes occur is {(1)+(2)):
It is said that (3)=7:3. Of these (1)
As a countermeasure against this, the voltage applied between the wire and the base metal at the time of arc start should be DC10 lower than the normal welding voltage.
There are methods to raise the temperature by about 0.07, but these methods have not been able to sufficiently prevent arc start errors. On the other hand, as a measure to prevent the causes (1) and (2) from occurring, there is a method commonly called a scratch start. This method involves starting the arc while the torch is running without stopping the torch at the start of welding. In other words, when the wire is fed out, it makes linear sliding contact with the base material rather than point contact, thereby destroying the surface insulation coating of the wire or base material and reducing contact resistance. However, this method has the problem that the positions where arcs are generated and weld beads begin to form vary, resulting in a decrease in quality. The reason for this is that the length of the wire protruding from the tip at the end of pre-welding is generally not controllable and varies by about 5 lIlm to ioms, and the wire feeding speed at the time of arc start is approximately 20m/sec to 30wa/sec
This is because it is quite fast. For example, if the running speed of the torch, that is, the welding speed is 1 2
Set at 0 am/win (20 m/sec),
Assume that the distance between the chip and the base material is set at 15-. Assuming that when the torch approaches a certain welding start point, there is a low difference in the length of the wire protruding from the tip, and the wire feeding speed is 2 5 m+/sec,
The time the wire is in contact with the base material is 1 0/2 5= Q
, 4 seconds will occur. During that time, the torch is traveling on the welding line at 20 an/sec, so the speed is 20 m/secX 0. 4 seconds
= 8 An variation in the start position will occur. This variation is at a level that is not permissible under normal manufacturing standards. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an arc welding robot that can reliably start the arc at the welding start point. [Means for Solving the Problems] To achieve the above object, the present invention supports a torch to which a consumable electrode is fed, moves the torch according to a taught program, and turns the welding machine's power supply on. In a control device for an arc welding robot, when the torch reaches a taught welding start point, the torch is temporarily stopped, an arc start signal is sent to the welding machine, and at the same time the torch is almost connected to the welding line. The torch is made to vibrate in simple motion with a minute amplitude in orthogonal planes, and when an arc start confidence signal is received from the welding machine, the torch is returned to the welding starting point and moved toward the next teaching point on the welding line. It is equipped with a circuit.

[Effect]

According to the above configuration, by causing the torch to perform simple harmonic vibration at a minute amplitude while generating an arc at the welding start point, the surface insulation coating of the base metal or wire at that part is destroyed, arc start is performed reliably, and the arc When the start confidence signal is issued, the torch returns to the welding starting point,
The simple harmonic motion stops and welding is performed while moving to the next teaching point.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. An embodiment of the present invention is shown in Figs. 1 to 4. As shown in Fig. 4, the robot system of a general arc welding machine consists of a robot control device 1, a welding machine 2, a torch 5, and a robot body 6. The torch 5 attached via the arm 7 is moved according to the taught program. At the same time, arc start signals and arc start confirmation signals are exchanged with welding machine 2. Then, the welding machine 2 supplies a welding current between the wire 8 fed to the torch 5 and the workpiece 9 to perform arc welding.

Fig. 1 shows a control algorithm according to this embodiment, Fig. 2 shows a welding part model, and Fig. 3 shows an operation sequence based on this algorithm.

When the torch 5 reaches the arc start point Pi, an arc start command is sent from the robot control device 1 to the welding machine 2, and at the same time, the torch 5 temporarily stops at the arc start point Pe. Next, guide point P for weaving. Read. This guide point P0 is a point for determining the working distance ΔA and direction when applying weaving at the arc start point P4, and this point is to be additionally taught by the teaching operator. The robot language (command word) when teaching this guide point P0 on software is to newly install a switch or the like and set the point with this switch instruction to P. Suppose that This point P0 is a point separated from the weld line EO by a minute distance ΔA in a plane that includes the arc start point PY and is substantially perpendicular to the weld line 10. Next, when reading the guide point P0 is finished, the robot's
Weaving between P and P0 is started using the Y and Z 3 axes, and when arc start is confirmed by the welding machine 2 and an arc start confirmation signal is input to the robot control device Ml, the torch 5 moves to the arc start point Pl. Reach. If the arc start and arrival at the arc start point P1 are not confirmed, continue until each is confirmed. When it is confirmed that the torch 5 has reached the arc start point P, the weaving operation is stopped, the next step position data is read, and the weaving starts moving toward the next teaching point on the welding line. Although not shown, the frequency during weaving is stored in the parameters of the welding program.

The flow indicated by the dotted line in Figure 1 shows the conventional control method. According to this embodiment, arc start point P1 of arc welding
By weaving the torch at , the surface of the wire or base material I1! Since the edge coating is destroyed to reduce contact resistance, it is possible to prevent arc start errors from occurring. [Effects of the Invention] According to the present invention described above, since a circuit for weaving the torch at the arc start point is provided in the control device of the arc welding robot, it is possible to prevent arc start errors from occurring.

[Brief explanation of drawings]

FIG. 1 is a flowchart according to an embodiment of the present invention;
The figure is a perspective view showing an example of the welding part, FIG. 3 is a time chart showing the operation sequence, FIG. 4 is a configuration diagram showing a general arc welding robot system, and FIG. 5 is a robot control device. FIG. 6 is a block diagram showing the flow of signals exchanged with the welding machine, and a time chart showing the operation sequence of arc start processing according to the prior art. 1... Control device, 2... Welding machine, 3... Arc start signal, 4... Arc start confidence signal, 5... Torch, 6... Robot body, 8... Wire ( Consumable electricity) 1 0... Welding line. Agent Tetsuro Abe Figure 2 Figure 1 Figure 5

Claims (1)

[Claims] (1) In an arc welding robot control device that supports a torch to which a consumable electrode is fed, moves the torch according to a taught program, and controls the power source of a welding machine, a taught welding starting point is used. When the torch reaches , the torch is temporarily stopped, and an arc start signal is sent to the welding machine.At the same time, the torch is made to vibrate in a simple vibration with a minute amplitude in a plane substantially orthogonal to the welding line, and the welding machine 1. A control device for an arc welding robot, comprising a circuit for returning the torch to a welding start point and moving the torch toward the next teaching point on the welding line when an arc start confirmation signal is received from the welding point.