< MIG WELDING
PLASMA CUTTING
Plasma cutting equipment superficially resembles MIG and TIG arc welding sets in many respects; a power unit, transformer, torch, return lead and pressurised gas or air supply are essential to the plasma cutter’s operation. Rather than joining metals however, plasma equipment is designed to cut (although there is a related PLASMA WELDING process). Unlike the more common OXY-GAS cutting system, a plasma arc system can effectively cut through any material capable of conducting an electric current – this includes stainless steels, copper alloys, aluminium alloys and most other cast metals and alloys.
The equipment works by initiating an arc between an ELECTRODE, and a conductive (copper) nozzle. Both of these items are mounted inside the head of the torch. When the cutting circuit is closed by depressing a torch-mounted switch, the arc jumps from the torch head to the workpiece.
A regulated gas is supplied to the torch head, either from an air compressor (AIR PLASMA CUTTNG), or else a high pressure cylinder (argon mixed with hydrogen or nitrogen is usual). The compressed gas passes through the torch head via a constriction in the conductive nozzle, before being ejected as an IONISED PLASMA JET at a temperature approaching 45,000°F (25,000°C). The ionised plasma jet is directed from just above the workpiece, crossing an arc gap of a few millimeters, before passing through the workpiece to produce a clean, accurate cut. A cut can be made through material of up to 1 inch (25mm) or so in thickness (CARBON STEEL), using professional level three phase equipment.
Despite it’s proven versatility in cutting a wide range of both non-ferrous and ferrous metal alloys, the use of plasma cutting equipment is not especially common in art foundries. This is possibly due to the expense of purchasing the equipment, which can be considerable, and the fact that most cutting operations in the foundry (removing runners, risers etc), can be more than adequately carried out by FRICTION with an abrasive disc mounted on an angle grinder. On the other hand, those studios and workshops with an extended facility to fabricate wrought material (including designs fashioned from brass and phosphor bronze sheet and other sections), will almost certainly find the plasma cutter a useful, if not essential piece of equipment, due to the quality of cut that can be achieved, and low levels of distortion – especially in light gauge materials.
STUDIO WELDING & CUTTING >
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