High speed arc welding robot cell

Citation

(1998), "High speed arc welding robot cell", Industrial Robot, Vol. 25 No. 3. https://doi.org/10.1108/ir.1998.04925caf.001

High speed arc welding robot cell

High speed arc welding robot cell

Keywords Arc welding, High speed, Robots, Welding

At the International Robot Exhibition 1997 in Tokyo, Japan, Yaskawa Electric unveiled a super fast (4m/min) arc welding robot cell, Motopac-WH200, the welding speed of which is four times faster than that of the conventional arc-welding process.

It consists of:

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  A Motoman K 6 or 16 robot

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  A Motoweld H5000 welding power source

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  A servo-torch

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  A laser-finder, a laser-tracker, a fixture, etc.

The secret of this ultra high speed welding lies mainly in a specially designed power source and servo-torch.

Up to now arc-welding robots have been using conventional, off the shelf welding power sources originally designed for a manual or semi-automated welding process. To accomplish higher speed arc-welding which human workers cannot achieve, Yaskawa has developed a special power source exclusively for the use of a high speed welding robot. As a result of extensive study on arc welding phenomena, an algorithm has been developed which enables fine control of the wave-form of the welding current during the short-circuit state and the sputtering is minimized even with this higher speed welding.

Another secret is the development of a servo-torch. Yaskawa adopts its newly developed, smaller, lighter, servo-motor (half in size and weight) to feed welding wire automatically. Taking advantage of the light weight of the welding wire feeding mechanism, Yaskawa mounts it at the very top end of the robot arm, next to a welding torch. With the conventional layout, the distance between an arc-welding torch and a wire feeding mechanism causes dead-time in the response of wire control. The idle wiring between them results in unstable wire feed depending on the posture and position of the robot arm. The new system eliminated these problems and enables the wire feeding speed to go higher (up to 28m/min; twice as fast as before).

High speed arc welding robot with a jig robot

According to Yaskawa, with the new power source alone, a welding speed of 3m/min is achieved. Together with a servo-torch further improvement by 1m/min is added so that an unprecedented high speed welding of 4m/min is realized.

The new controller can control two robots in co-ordination so that you can use one robot as an arc welding robot and the other as a jig robot to eliminate an expensive fixture which holds an object to be welded.

Teaching the welding operation can be done by direct-teach mode: a human worker pulls and guides the top end of the robot arm to go through the trajectory of the welding path. With the aid of a welding expert system built into a lap-top personal computer, a nonskilled worker can teach the welding conditions easily.