Page 140 - Welding of Aluminium and its Alloys

MIG welding 125

7.9 Microprocessor-controlled inventor-based twin wire pulsed MIG
power sources. Courtesy of TPS-Fronius Ltd.

instance, being capable of being made at travel speeds of over 2 metres per
minute.The welding torch is large, making access a problem, and the capital
cost of the equipment is high.

7.2.2 Wire feeders and welding torches

7.2.2.1 Welding torches

The MIG process requires the filler wire to be delivered to the welding
torch (Fig. 7.10) at a fixed speed and for the welding current to be trans-
ferred to the wire via a contact tip within the torch. The torch must also be
equipped with a means of providing the shield gas and of enabling the
welder to commence and end the welding sequence. This is generally
achieved by means of a trigger on the handle of the torch. Operating
the trigger initiates the shielding gas flow and the welding current when
the wire tip is scratched on the workpiece surface.This, in its turn, starts the
wire feed. Releasing the trigger stops the wire feed and shuts off the current
and shielding gas. The heat generated in the torch during welding may also
require the torch to be water-cooled. All of these services must be deliv-
ered to the torch via an umbilical cable containing a wire feed conduit,