Plasma cutting cuts conductive metals with a jet of ionised gas, the plasma, brought to a temperature of around 20,000 °C by an electric arc. The arc melts the metal and the high-speed jet expels the molten material from the kerf. Only conductive materials, such as steel, stainless steel, aluminium and copper, can be cut this way.
The machine combines a CNC cutting table, a power source and a torch, with a system that keeps the torch height constant above the sheet. The gas depends on the metal and the quality aimed for: air, oxygen, nitrogen or an argon-hydrogen mix. Plasma cuts from thin sheet up to several tens of millimetres thick. Its edge is rougher and more tapered than a laser’s, with a heat-affected zone; high-definition torches and underwater cutting improve the result and limit fumes. Plasma is also used to cut weld bevels, preparing edges before welding.
Plasma is often more economical than laser on medium to thick sections. It dominates heavy sheet work, plate fabrication, structural steelwork, and base plates, side plates and machine plates. When edge accuracy matters, it is reserved for parts that are afterwards machined or ground, or you turn to laser cutting or waterjet cutting. The parts are then assembled by MIG-MAG welding. The guide laser, plasma or waterjet compares the three processes; see also the sheet metal and cutting page.
In a quote request. State the grade and thickness of the sheet, attach the DXF and specify the cut quality required (ISO 9013 grades it). If the part is machined after cutting, leave a machining allowance. Mention any bevel preparations (angle, joint type) and the quantity: on large plates, nesting the parts reduces scrap.