CNC plasma tables

A CNC plasma table cuts electrically conductive metal with a narrow arc of ionized gas, moved over the plate by a CNC gantry. It is a common choice for mild steel plate from thin sheet to several centimetres thick, and suits fabricators, trailer and farm equipment builders and structural shops where plate thickness matters more than laser-fine detail.

How plasma cutting works

Gas flows through the torch around an electrode. A pilot arc forms between the electrode and the nozzle, ionizes the gas and then transfers to the workpiece, which completes the electrical circuit. The nozzle constricts the arc into a very hot, high-velocity jet that melts the metal while the gas blows it out of the cut, as Hypertherm describes the process. Only conductive metals can be cut: mild steel, stainless, aluminium, copper, brass and other alloys.

The parts that form and shape the arc, mainly the electrode, nozzle and swirl ring, wear in use and are replaced regularly. A torch height control keeps the torch at the right distance as the plate warps and heats; the Accurl CPL-1530, for example, pairs a Hypertherm XPR300 source with ArcGlide height control and an EDGE Pro CNC.

Types of plasma

Table sizes and machine classes

How to choose

• Thickness: pierce, not only severance. The headline maximum is a severance figure; pierce capacity is lower. The XPR300 cuts mild steel up to 80 mm but pierces 45 mm with oxygen, or 50 mm with argon assist. Size the amperage to the plate you pierce every week.
• Cut quality. Decide which parts need tight tolerances, square edges or small holes. High definition and X-Definition sources narrow the gap with a laser on thicker plate, while air plasma suits parts that are welded or ground anyway.
• Gas for stainless and aluminium. Hypertherm suggests nitrogen plasma with a nitrogen or water shield on stainless under 5 mm, F5 with a nitrogen shield from 5 to 12 mm, and hydrogen mixes above 12 mm. That means extra gas supply and a gas console that can handle it.
• Bevel. A bevel head cuts weld preparations on the table; Kinetic offers plasma, oxy-fuel and triple oxy-fuel bevelling, and Messer offers plasma bevel units.
• Extra processes. Drilling and tapping stations, oxy-fuel torches for plate beyond plasma range, and on some gantries a fiber laser head. The K2500 carries a six-station drilling turret for holes up to 19 mm (3/4 in).
• Motion and frame. Servo drives, rack and pinion quality and gantry stiffness decide accuracy on large tables.

For work that mixes thin sheet with plate, weigh plasma against a fiber laser; our fiber laser versus plasma comparison sets out where each process fits.

What your plant needs

• Power. Production sources draw heavily: Hypertherm lists the XPR300 at a power factor of 0.98 at 66.5 kW. Check the input voltage of the source, CNC and fume collector against your 600 V three-phase supply, and see 600 V power for imported machines.
• Air and gas. Air plasma needs a steady supply of clean, dry, oil-free compressed air. High definition systems need oxygen and nitrogen, and argon, F5 or hydrogen mixes for stainless and aluminium.
• Water table or downdraft. A water table holds water under the plate to catch sparks, dust and much of the fume, as on the Torchmate 4800, but leaves sludge to remove. A downdraft table pulls fume down through zones under the cut into a dust collector; Kinetic and Accurl use this approach, and Messer works with Camfil and Donaldson collectors.
• Fume control. A study of stainless steel plasma cutting archived by the US CDC found hexavalent chromium, a carcinogen, in the fume, with fume output rising with arc current and Cr(VI) emissions higher than a previous welding fume study. CCOHS also flags nickel in stainless fume and zinc oxide from galvanized steel. Extraction is part of the machine, not an extra.
• Floor. Large gantries need a level foundation along their full travel, while unitized designs such as the MetalMaster Xcel keep floor rails out of the loading path. See our floor preparation guide.

Running costs and consumables

• Torch consumables. Electrodes and nozzles wear fastest, and their life depends on amperage, the number of pierces and how the arc starts and stops. Hypertherm says the XPR design extends consumable life by eliminating ramp-down errors, and Lincoln Electric publishes a consumable cost calculator for its Torchmate range.
• Gas and compressed air, including the compressor's electricity and dryer maintenance.
• Electricity for the source, drives and fume collector.
• Table slats, which erode and are replaced; Kinetic uses modular slats for quick change-out.
• Water or filter upkeep: sludge removal on water tables, filter cartridges on downdraft collectors.
• Edge finishing: dross removal and grinding when the process does not match the edge quality your parts need.

Typical applications

Plasma tables cut base plates, gussets, brackets and flanges for structural steel; frames, hitches and panels for agricultural and trailer manufacturing; wear parts and repair plates for heavy equipment; and decorative steel signs on smaller tables. On large machines, bevel and drilling heads deliver weld-ready, drilled plate parts without a second setup.