Air-cooled MIG torch eases aluminium welding

Aluminium is notoriously difficult to arc weld, but a new, air-cooled torch with servo-powered wire feeding is capable of wire feed speeds of over 34m/min and has a 'push-pull' wire feeder.

With manufacturers particularly in the automotive industry using more and more aluminium, which is notoriously difficult to arc weld, Motoman has developed a new, air-cooled torch with servo-powered wire feeding specifically for this application.

Called SAWK-350, its cost is equivalent to that of a standard torch, yet it is capable of wire feed speeds of over 34m/min - nearly double that of conventional torches and approaching the speed of "rapid arc" systems, which unlike SAWK-350 need a special power source.

Apart from the metallurgical difficulties of welding aluminium, another problem is that the wire is soft and difficult to push.

This makes conventional 'push' wire feed systems, which are mounted up to one and a half metres from the torch at the back of the robot arm, both slow and prone to wire stall.

The former reduces productivity while the latter leads to loss of quality by causing variations in arc stability in the weld pool.

Motoman has resolved these issues by making SAWK's wire feed system 'push-pull', powering it by an external servo motor, and wrist-mounting the assembly no more than 500mm from the weld tip of the torch.

In combination with a pneumatic clutch fitted to the aluminium wire payoff pack, the result is very accurate wire feed of better than 0.5 per cent.

There is also rapid response to arc-on and arc-off conditions, as all parameters are synchronised by Motoman's XRC controller.

Quality improvements are particularly noticeable when welding thin material, not only aluminium but steel as well.

Production trials have now been completed in Sweden where the torch is manufactured by Motoman - the only robot company in the world to make its own welding torches.

To assist access to difficult areas such as inside a car chassis, the torch has a slimline design and weighs just 4.4kg.

Aluminium wire in the diameter range 0.6 - 1.2mm can be accommodated and the bobbin is 100mm wide by up to 300mm in diameter.

The air-cooled torch neck is interchangeable, nozzle diameters from 13 to 15mm may be used, nozzle cleaning equipment is provided and so too is a collision detection unit.

The power source needed is 350A at 100% duty cycle.

(This was Manufacturingtalk's Top Story on 22 April 2002).

(This was Manufacturingtalk's Top Story on 23 April 2002).

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