A CNC plasma table is a computer controlled machine that cuts electrically conductive metals using a high temperature plasma arc. It is important in workshops because it can make accurate shapes from steel, aluminum, and stainless steel much faster than hand cutting. The machine combines electrical power, compressed gas, motion control, and digital design files.
Learning how it works helps students connect physics, engineering, and safe manufacturing practice.
Key Facts
- Plasma is an ionized gas that conducts electricity and can reach temperatures above 20,000 °C.
- Cutting speed depends on material thickness, amperage, gas flow, and desired edge quality.
- Electrical power is P = VI, where P is power in watts, V is voltage, and I is current.
- Kerf is the width of material removed by the cut, often about 1 to 2 mm on workshop plasma tables.
- Feed rate can be estimated by v = d/t, where v is cutting speed, d is cut distance, and t is time.
- A CNC plasma table needs a conductive work clamp so the arc circuit can close through the metal sheet.
Vocabulary
- CNC
- CNC means computer numerical control, where a computer directs machine movement using programmed coordinates.
- Plasma Arc
- A plasma arc is a stream of ionized gas that carries electric current and melts metal along the cut path.
- Gantry
- A gantry is the bridge-like moving structure that carries the cutting torch across the table.
- Kerf
- Kerf is the gap left behind by the cutting process and equals the width of material removed.
- Torch Height Control
- Torch height control is a system that keeps the plasma torch at the correct distance from the metal surface during cutting.
Common Mistakes to Avoid
- Ignoring kerf compensation gives parts that are too small or too large because the plasma arc removes a measurable width of metal.
- Using the wrong feed rate causes poor cuts because moving too fast may not fully pierce the sheet, while moving too slowly can widen the kerf and overheat the edge.
- Forgetting the work clamp prevents a stable arc because the electrical circuit must pass through the metal sheet and return to the power supply.
- Setting torch height by eye leads to inconsistent quality because arc voltage, pierce height, and cut height must match the material and amperage.
Practice Questions
- 1 A CNC plasma table cuts a 900 mm straight line in 18 s. What is the cutting speed in mm/s and in mm/min?
- 2 A plasma cutter operates at 120 V and 45 A during a cut. Use P = VI to calculate the electrical power in watts and kilowatts.
- 3 A student notices heavy dross on the bottom edge of a steel part after cutting. Explain how feed rate, torch height, or amperage could cause this problem and name one adjustment to try.