Plasma and waterjet are both used on steel plate, and a lot of fabrication shops run plasma for good reason: it is fast and it is cheap. Waterjet costs more per metre. The question is what the extra buys you on a particular part.
Part Engineering cuts with an abrasive waterjet in Osborne Park. We do not run plasma, and for plenty of rough-profile mild steel work plasma is the sensible choice.
How each one cuts
Plasma sends an electric arc through a jet of gas. The arc heats the gas into plasma hot enough to melt the metal, and the gas blows it out of the cut. It only works on material that conducts electricity.
Abrasive waterjet erodes the material with water at around 60,000 psi carrying garnet. No arc, no melting, and no need for the material to conduct.
Where plasma wins
- Speed and price on mild steel plate. For profiles where a rough edge is fine, plasma is hard to beat.
- Work that will be welded and ground anyway. If the edge is getting a weld prep and a grinder, plasma's edge quality may not matter.
- Site and field work. Hand-held plasma goes where a waterjet cannot.
Where waterjet wins
- Accuracy. Plasma's kerf is wider, its edge can bevel, and holes tend to come out tapered or slightly undersized. Waterjet holds tighter dimensions, and our Tilt-A-Jet head controls taper so walls come off square.
- Holes that need to fit. Bolt holes cut by plasma in thick plate often need drilling out. Waterjet holes are usually ready for the bolt.
- No heat-affected zone. Plasma hardens and softens the steel along the cut and leaves dross to clean off. On wear plate and heat-treated steel, the softened edge is where the part wears first. Waterjet leaves the edge at the hardness you paid for.
- No warping. Heat moves thin and long parts. A cold cut does not.
- Anything non-conductive, and much more. Plasma cuts conductive metals only. Waterjet also cuts stone, glass, rubber, plastics, and composites.
Edge quality and cleanup
A plasma edge usually has some bevel, a hardened skin, and dross on the underside. That is fine for structural work and costly when the part needs a machined fit afterwards.
A waterjet edge is even and satin-finished with no dross and no hardened layer, so a later drill, tap, or weld is not fighting the edge.
A quick way to decide
- Mild steel, rough profiles, being welded and ground: plasma.
- Holes that must fit, tighter tolerances, or a part that cannot warp: waterjet.
- Wear plate, hardened steel, stainless where the edge matters, aluminium, or titanium: waterjet.
- Anything that is not metal: waterjet.
Send the drawing through the quote page with material and thickness, or read about the waterjet service.