CNC Plasma Cutting Table Product

Overview

Plasma cutting is a thermal cutting process using an ionized gas (plasma) at temperatures exceeding 20,000 K, driven at high velocity by a constricted electric arc, to melt and remove metal. A CNC plasma table automates this process, guiding the torch across a sheet following CAD-generated tool paths to cut parts to precise, repeatable dimensions.

The process is fast (2–7 m/min), cuts through both electrically conductive metals (steel, stainless, aluminum, copper), and produces a narrow, relatively clean kerf (cutting gap). Unlike oxy-fuel cutting, plasma requires no preheat and works on thin as well as thick materials. Like laser, it is sensitive to nozzle standoff distance, so modern systems use automatic height control to maintain the optimal arc voltage and torch gap.

The Gantry Frame is a precision CNC machine tool adapted for plasma. The Plasma Cutting Torch holds the consumable electrode and nozzle. The Plasma Power Supply supplies DC current at constant amperage. The Gas Supply & Distribution delivers ionized plasma gas and shielding gas. The Automatic Height Control maintains the arc voltage (arc voltage directly indicates torch height). The X-Y Motion System positions the torch via CNC Controller & Operator Panel.

How it works

A sheet of steel or aluminum (1–12 mm thick, or thicker on specialized systems) is placed on the Work Table & Surface—a grate of replaceable slat bars allowing the cut kerf and dross to fall through into the Water Collection Tray below.

The operator loads a CAD-generated cutting program into the CNC Controller & Operator Panel. The program contains the toolpath—the XY coordinates of the cut, optimized to minimize nesting waste and torch travel.

The machine starts. The Gas Solenoid Valve opens, flowing Gas Supply & Distribution gas (air, nitrogen, or argon) to the Plasma Cutting Torch at 3–6 bar, directed through the Swirl Ring to impart rotation. Simultaneously, the Plasma Power Supply is commanded to standby: the cnic-plasma-arc-starter circuit generates a high-frequency high-voltage (4–8 kV) signal to break down the gas and initiate an arc between the Cathode Electrode (typically tungsten or hafnium) and the workpiece.

Once the arc is established, the Plasma Power Supply takes over, supplying a steady Current Monitor (typically 30–125 A for cutting up to 6 mm steel). The arc heats the gas flowing through the Plasma Nozzle opening (0.8–1.6 mm) to a plasma state—a partially ionized gas exceeding 20,000 K. This plasma exits the nozzle in a high-velocity jet, melting the metal at the cut location.

As the cnc-plasma-torch is positioned over the sheet by the X-Y Motion System, the molten metal is blown away by the plasma jet, creating a kerf (cutting gap). The torch is positioned 2–5 mm above the workpiece surface—the optimal standoff distance for cut quality. The Automatic Height Control maintains this gap automatically: the system measures the arc voltage (which varies predictably with standoff), compares it to a setpoint, and adjusts the Height Servo Motor to raise or lower the torch if the voltage drifts, keeping the gap constant even as the surface of the workpiece varies slightly or tilts.

The Gantry Frame is driven by the X-Y Motion System: the X-Axis Motor and Y-Axis Motor are CNC-coordinated, translating the torch along the programmed cutting path at a feedrate of 2–7 m/min (for steel; aluminum typically cuts 30–50% faster). The X Rail and Y Rail precision guides ensure straight edges, and the X Ballscrew and Y Ballscrew convert stepper or servo motor steps to tool motion with repeatable accuracy (typically ±1–2 mm).

As the cut progresses, molten metal and oxidized dross (spatter) fall through the Slat Grate into the Water Collection Tray. A downdraft Exhaust Duct & Fan pulls the smoke and fumes away. The water tray circulates cool water to quench the hot dross and reduce noise.

The Shield Cup and Swirl Ring direct shielding gas (secondary gas, 10–40 L/min) around the arc, protecting it from oxygen in the air, which would otherwise cool the arc and degrade cut quality. For high-speed, high-quality cuts (aerospace and marine applications), nitrogen or argon shielding is used; for lower-cost production cutting, compressed air (using the primary plasma gas and no secondary shielding) is acceptable.

Cutting speed depends on:

• Amperage: Higher amperage cuts faster and thicker material. A 45 A system cuts 1–2 mm mild steel at 4–5 m/min. A 200 A system cuts 12–15 mm plate at similar speeds or faster.
• Material: Mild steel cuts fastest; stainless and aluminum are slightly slower. Copper and brass are slower still.
• Thickness: Thicker material requires lower feedrate and higher amperage.

Cut quality (straightness, surface finish, kerf taper) is controlled by:

• Torch height (2–5 mm; too low = narrow kerf; too high = poor cut quality)
• Feedrate (too fast = incomplete melting, dross on bottom; too slow = excessive heat, wide kerf)
• Nozzle orifice size (smaller = finer cut but lower cutting speed; larger = faster but rougher)

Once the cutting is complete, the part cools naturally. The torch retracts, and the next part is loaded. The Slat Bar elements are inspected for wear and replaced periodically, as the plasma jet slowly erodes them.

CNC plasma tables are workhorses in steel fabrication shops, aerospace suppliers, and job shops, cutting everything from simple brackets to complex aerospace engine cowlings. The combination of speed, quality, automation, and low capital cost makes plasma cutting the dominant thermal cutting method for metal fabrication today.