A plasma cutter is a workshop machine that cuts electrically conductive metals using a narrow jet of superheated ionized gas. The torch creates a bright plasma arc that melts a thin path through steel, aluminum, copper, and other metals. This tool matters because it can make fast, clean cuts in thick or irregular metal parts with less mechanical force than saws or shears.
It is common in fabrication shops, auto repair, construction, art metalwork, and industrial manufacturing.
Inside the torch, compressed gas is forced through a small nozzle while an electric arc adds enough energy to turn the gas into plasma. The plasma reaches extremely high temperatures, melts the metal along the cut path, and blows molten metal out of the kerf. Because the workpiece must carry electric current, plasma cutting only works on electrically conductive materials.
Cut quality depends on current, travel speed, gas flow, torch height, and the thickness and type of metal.
Key Facts
- Plasma cutting uses an electric arc and compressed gas to form a superheated plasma jet.
- It cuts only electrically conductive materials such as steel, stainless steel, aluminum, brass, and copper.
- Electrical power is calculated by P = IV, where P is power, I is current, and V is voltage.
- Energy used during a cut is E = Pt, where E is energy, P is power, and t is time.
- Kerf is the width of material removed by the cut, so final dimensions must allow for kerf width.
- Higher current and slower travel speed add more heat, which can increase cut thickness but may also increase dross and warping.
Vocabulary
- Plasma
- Plasma is an ionized gas made of charged particles that can conduct electricity and transfer large amounts of thermal energy.
- Kerf
- Kerf is the narrow slot or width of material removed by a cutting process.
- Arc
- An arc is an electric current flowing through a gas between two points, producing intense heat and light.
- Dross
- Dross is the rough solidified metal that can stick to the bottom edge of a plasma cut.
- Torch Height
- Torch height is the distance between the plasma torch nozzle and the workpiece surface during cutting.
Common Mistakes to Avoid
- Cutting nonconductive materials with a plasma cutter is wrong because the arc needs an electrically conductive workpiece to complete the circuit.
- Ignoring kerf width is wrong because the cut removes material, so the finished part can become too small if dimensions are not adjusted.
- Moving the torch too slowly is wrong because excess heat can widen the cut, create more dross, and warp thin metal.
- Using the wrong air pressure or gas flow is wrong because an unstable plasma jet can cause rough cuts, poor penetration, and faster nozzle wear.
Practice Questions
- 1 A plasma cutter operates at 40 A and 120 V while making a cut. What electrical power does it use in watts?
- 2 A cut takes 25 s using a plasma cutter with an electrical power of 4800 W. How much energy is used during the cut in joules?
- 3 A student tries to use a plasma cutter on a ceramic tile and gets no proper cut. Explain why the tool is not suitable and name two materials it would cut instead.