Can a CNC plasma cutting machine cut stainless steel and aluminum?

Can a CNC plasma cutting machine cut stainless steel and aluminum?

Yes. Plasma melts any electrically conductive metal, which is why it handles stainless, aluminum, copper alloys and cast iron that an oxygen flame simply cannot cut. What changes is the gas and the current, not the machine. Mild steel is normally cut with oxygen or clean compressed air for speed. Stainless steel (304, 316) is cut with compressed air or nitrogen: air is cheapest but leaves a dark oxidized face, nitrogen gives a cleaner, less oxidized edge at higher gas cost, and argon-hydrogen mixtures or F5-type mixtures give the bright silver edge used for sanitary and architectural work. Aluminum is cut with air or nitrogen and never with oxygen - it needs more current per millimetre because it conducts heat away from the kerf very fast, so the kerf tends to run wider. On a 300 A IGBT plasma source rated for 1-25 mm, treat stainless and aluminum as a 1-20 mm quality range rather than the full mild steel range. Whichever gas you choose, if the part goes straight to welding, grind or machine the cut face first: air-plasma edges carry a nitride and oxide layer that causes porosity in the weld.

How thick can I cut before the edge stops being usable?

Separate the quality range from the severing range - confusing the two is the most common buying mistake. On a 300 A mechanised plasma source, mild steel gives a quality cut up to about 25 mm; beyond that the arc still severs the plate but the bevel grows towards 3-5 degrees per side, dross becomes heavy and the heat-affected zone deepens, so the part needs grinding that costs more than the cutting saved. Stainless and aluminum reach their practical ceiling earlier, typically around 15-20 mm, because dross and bevel get hard to control. Above the plasma range, use the flame torch on the same gantry: a combined flame and plasma gantry covers flame 6-60 mm and plasma 1-25 mm, and in the overlap band of roughly 6-25 mm you choose by economics - plasma wins on speed and edge quality, flame wins on gas cost and on very thick sections. Only flame will take you past about 60 mm, and past 100 mm you are into specialist oxy-fuel territory with preheat and slow travel.

Why does my kerf get wider during a shift and the parts come out oversize?

Almost always consumable erosion, not the machine losing position. A new nozzle might have a 1.2-1.5 mm orifice; after a few hundred pierces at 300 A that orifice opens towards 1.6-1.8 mm. A wider orifice makes a wider kerf and a softer, less coherent arc, so parts grow oversize, the edge bevels and dross increases. The electrode matters just as much: once the hafnium insert is cratered the arc wanders and the cut face becomes uneven rather than simply wide. Diagnose with a measurement, not with your eyes - cut a 100 mm square, measure it with a caliper against the drawing, and inspect the bevel with a gauge. If the part is more than about 0.3 mm oversize and the edge is bevelled, change nozzle and electrode as a matched set; changing only the nozzle rarely fixes it. Other contributors to watch: moisture in the air line attacking the electrode, torch standoff drifting because the height control is not tracking, and pierce height set too low so splash-back damages the shield. Log arc hours per consumable set so replacement is scheduled, not reactive.

Should I plasma-cut holes or drill them?

Use a ratio, not a habit. If the hole diameter is at least 1.5 times the plate thickness, a plasma-cut hole will generally pass a bolt gauge and is far faster than drilling. Below that ratio the natural taper of the arc - roughly 2-3 degrees per side - becomes obvious, the hole comes out undersized at the bottom and out of round, and no amount of parameter tuning fixes it. The smallest hole a plasma torch can produce is about 1.5 times the kerf width, so with a 1.5 mm kerf you are realistically looking at 2.5 mm and up. The practical structural-steel workflow is: plasma the hole 1-1.5 mm undersize, then drill or ream to final size, which is much cheaper than drilling from solid and keeps slip-critical bolted connections within specification. For holes under 10 mm in plate over 10 mm thick, plan on drilling. Also keep the pierce point 3-5 mm outside the hole edge on thin plate so the pierce crater and splash do not damage the finished bore.

Does plasma cutting damage the edge for welding or bending?

It creates a heat-affected zone, but for structural work that is usually harmless. On 6-12 mm mild steel the HAZ is roughly 0.2-1.0 mm deep and slightly harder and less ductile than the base plate, which is acceptable for welded plates and beams. It matters in two situations. First, if the part is bent through a tight radius at the cut edge, the hardened layer can crack, so remove about 1 mm from that edge before forming or cut that edge with lower current and fine-cut consumables. Second, for alloy steels such as 4130 or 4140 under fatigue loading, or where the drawing specifies hardness, machine off the HAZ or plan a stress relief. On stainless, air-plasma cutting leaves a nitride and oxide layer that reduces corrosion resistance, so grind it back and pickle or passivate before the part goes into service or gets welded. On aluminum, remove the bottom dross and machine any weld prep face that has an X-ray or radiographic acceptance requirement, because the re-formed oxide film traps porosity.

What tolerance should I put on plasma-cut parts on the drawing?

Be honest about the process. A servo-driven gantry with a stated length accuracy of about plus or minus 1.0 mm will typically hold plus or minus 0.5 mm on profile position and around plus or minus 0.3 mm hole-to-hole on a well-tuned machine in 6-10 mm plate, but kerf taper, consumable wear and plate flatness all add variance that no controller can remove. So specify plus or minus 1.0 mm on general profile dimensions, tighten to plus or minus 0.5 mm only where you can and will measure it, and never apply a machined-feature tolerance to a plasma-cut edge. Treat plasma as a first operation: cut profiles with 1-3 mm of machining allowance wherever a bore, bearing seat or mating face follows, then finish on a mill or drill. One more thing that catches people out on large parts - thermal growth. A 6 m long part cut from a hot plate late in the shift can measure 0.5-1 mm different from the same part cut first thing in the morning, so cut your critical long parts early and let the plate stabilise.

Do I need to prepare aluminum or stainless before plasma cutting?

Yes, and preparation is where most bad aluminum cuts come from. Aluminum forms an oxide layer within minutes of exposure to air, and that oxide does not conduct well enough for a stable arc, so the arc wanders, the kerf roughens and the cut quality becomes inconsistent. Wire-brush or flap-disc the cut line and degrease with acetone or isopropyl alcohol immediately before cutting - not the day before, because the film re-forms. On stainless, remove mill scale and oil, and never use a carbon-steel wire brush on it: embedded carbon particles become rust spots later. Equally important is the work return path: clamp the earth directly to the plate on bare metal, close to the cut, not to a slag-covered slat bed, because a poor return is the second biggest cause of erratic cuts after wet air. For galvanized plate, cut over a water table or with strong downdraft extraction - zinc fume is a genuine health issue - and remember that the zinc coating volatilises near the cut, so the edge needs re-protection before painting.

What cleanup is needed after plasma cutting before welding or painting?

Plan the finishing step into the routing, because a plasma edge is a semi-finished edge. First remove dross: soft, easily chipped dross usually means speed was slightly low, while a hard, brittle bead that needs a grinder means the arc ran too fast for the thickness - the difference tells you which way to correct the chart. Second, dress the edge: grind the cut face where a weld prep is required, and remove 0.5-1 mm of the oxide or nitride layer on stainless and aluminum before welding, then pickle or passivate stainless so the corrosion resistance is restored. Third, handle the plate surface - spatter and smoke deposits around the cut line interfere with coating adhesion, so they must be blasted or sanded off, not painted over. Fourth, on a water table, parts come out wet and can flash-rust within hours, so dry them and apply primer promptly. For structural work to EN 1090 or an equivalent coating spec, assume the cut edge will be blasted to Sa 2.5 anyway; designing the routing so the plasma edge is always followed by blasting saves a whole manual grinding operation.

Technical Specifications of CNC Gantry Plasma Cutting Machine

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Applications

The CNC Gantry Plasma Cutting Machine is widely applied in steel structure prefabricated buildings, bridge and infrastructure construction, shipbuilding and marine engineering, heavy machinery manufacturing, power plant and industrial facilities, and offshore wind power structures.

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For more information about CNC Gantry Plasma Cutting Machine and other steel structure intelligent equipment, contact YOMI CNC Cutting & Welding Machinery. Our team of experts is ready to help you find the best solution for your manufacturing needs.