JPH01157778A - Automatic welding method by arc sensor - Google Patents

Abstract

PURPOSE:To stably perform accurate welding by sensing a welding place in advance by a locus formed by composing circular motion or polygonal motion, etc., and then performing welding under necessary welding conditions based on this result. CONSTITUTION:While the locus 3 formed by composing motion in the direction along a joint 2 of a work 1 with the circular motion or the polygon motion being drawn by the torch tip, the welding place is sensed in advance to grasp accurately a proper shape of the work 1. Based on a result of sensing, the welding is then performed under the necessary welding conditions. By this method, since sensing can be executed at a stable current area, and accurate welding can be performed stably.

Description

[Detailed description of the invention] Industrial field of application In order to automate the arc welding process, it is necessary to automate the tacking of arc welding workpieces by automatically eliminating errors when fixing them to the workbench, errors caused by thermal distortion during welding, etc. must be corrected accordingly. For this purpose, a position sensor is required to detect the deviation of the actual position of the joint from the welding line that is previously taught to the automatic welding machine.

Various position sensors have been devised, one of which is an arc sensor that uses the welding phenomenon itself as a sensor. The present invention relates to an automatic welding method using this type of arc sensor.

BACKGROUND OF THE INVENTION The most common arc welding power source is a power source with constant voltage characteristics. The arc characteristics of this type of power source are such that when the arc length changes, the arc current and voltage change. On the other hand, since the joint to be welded has some shape change, the arc length changes due to this shape change, and therefore the current or voltage changes. Therefore, by observing the welding current or welding voltage, changes in the shape of the workpiece can be determined.

The above is the principle of the arc sensor, but in reality there are various noise components, and the changes in the current and voltage may not be clearly obtained. In particular, this applies to workpieces whose shape changes are small, such as workpieces made of stacked thin plates. Furthermore, the welding arc phenomenon itself is not stable; for example, there are cases where welding must be performed in a current range where short-circuit transitions occur frequently.

Conventionally, this problem has been dealt with by eliminating noise by modifying circuits or high-speed microcomputer software, or by changing the welding power source to one suitable for sensors.

Problems to be Solved by the Invention As explained above, the key point is to remove noise components.
The drawbacks were that the software for the high-speed microcomputer was complex and that a welding power source suitable for sensors was required. The present invention is to obtain a welding current or voltage that is originally low in noise by devising a weaving method.

Means for Solving the Problems In order to solve the above problems, the present invention swings the welding torch with a motion that combines a motion along the joint of the workpiece and a circular or polygonal motion. The method is characterized in that circular motion or polygonal motion is divided into several phases and welding is performed under welding conditions such as different currents, voltages, or circumferential speeds.

Effect: By the above-mentioned means, the preceding location in the direction of weld bead formation is sensed in a stable current state of arc phenomenon,
After that, welding is performed under the required welding conditions.

Since sensing is in a stable current range, it is possible to detect changes in current caused by changes in shape with few fluctuation components.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, 1 is the workpiece, 2 is the welding line of the lap joint, and 3 is the locus of the torch tip. FIG. 2 shows the trajectory of the torch tip when the movement in the welding line direction is excluded, where 4 is the welding line direction and 5 is the trajectory of the torch tip. In this FIG. 2, ■ and ■ represent each of the two divided circular motions. FIG. 3 schematically shows the rate of change in welding current. In FIG. 3, (a) shows a low current region, (b) shows a short circuit transition region, and (C) shows a spray region.

As shown in Figures 1 and 2, roughly speaking, the bead is located around the center of the circle. Therefore, when the torch tip is moving in the circular area (■), the shape of the workpiece is not destroyed by welding and has its original shape. This is welded with a pongee bead using the current shown in part (a) of Figure 3.

That is, the preceding location in the direction of weld bead formation is sensed in a stable current state of arc phenomenon, and then welding is performed under required welding conditions.

This state is repeated in the weaving cycle.

Since the current range is stable, changes in current caused by shape changes can be detected with few fluctuation components.

The pongee bead generated at this time is immediately replaced by a bead generated under normal welding conditions, so there is no problem. This allows stable sensing even when the desired welding conditions are within the range.

The welding conditions for region I are normal.

Although circular motion has been described here, any weaving that involves movement of the tip of the weld bead may be sufficient.

Effects of the Invention As described above, according to the present invention, it is possible to obtain welding current or voltage, which originally has little noise, as accurate sensing information.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main part showing the locus of the torch tip in an automatic welding method using an arc sensor showing an embodiment of the present invention; FIG. 2 is a plan view of the main part showing the locus of the circular motion of the torch tip; FIG. 3 is a characteristic diagram showing the rate of variation with respect to welding current. 1... Workpiece, 2... Welding line, 3...
...Trajectory of the tip of the torch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In an automatic welding method using an arc sensor, in which a welding torch is oscillated in a direction across a welding line, changes in arc current or arc voltage are detected, and a relationship between a joint of a workpiece and an arc generation position is determined, the welding torch is oscillated. The welding torch is oscillated by a motion that is a combination of the motion along the joint that would otherwise occur without the welding torch, and the motion of the tip of the welding torch in the circular or polygonal direction. An automatic welding method using an arc sensor, which is characterized by dividing motion into several phases and performing welding under different welding conditions such as current, voltage, or circumferential speed.