Plasma cutting torches are commonly used tools for cutting metals for a variety if purposes. A hand-held plasma torch works well to cut sheet metal, metal plates, straps, pipes, bolts, and other smaller pieces of metal quickly. They also work well for cutting small shapes from steel plate, gouging, back-gouging weld joints, or removing defective welds. However, a hand held plasma torch does not offer sufficient edge quality or part accuracy for most metal fabrication. As a result, a computer controlled plasma cutter is necessary. This is a machine that has a plasma torch that’s controlled by a computer.
How a Plasma Cutter Works
Plasma cutters work by creating an electrical channel of ionized gas through the metal being cut in order to form a complete electrical circuit back to the cutter itself by means of a grounding clamp. This is achieved by sending an electric arc through the gas, which is passed through a constricted opening or nozzle. The gas used can be nitrogen, argon, oxygen, or even shop air, depending on the type of metal that is being cut. The electric arc elevates the temperature of the gas to the point that it enters a fourth state of matter (the first three being solid, liquid, metal, and gas), known as plasma. Because the metal being cut is part of the electrical circuit, so the electrical conductivity of the plasma transfers the arc to the work.
The nozzle causes the gas to squeeze through at a high speed, which cuts molten metal. The gas also is directed around the perimeter of the cutting area in order to shield the cut. In higher end plasma cutters, a pilot arc between the electrode and nozzle is used to ionize the gas and generate the plasma before the arc transfer.
Machined Over Hand-Held Plasma Cutting
Computer controlled plasma machines generally use a different type of plasma system than hand-held ones. This system is specially designed for mechanized cutting. It uses a straight-barreled torch, which can be carried by a machine, and has an interface that can be controlled by a computer. Some entry-level machines can use a torch that is designed for hand-held cutting, but if serious manufacturing or fabrication is desired, then a mechanized torch and plasma system are necessary.
A computer controlled plasma cutter is capable of multi-axis cutting of thick material, which allows for complex welding seams that would not otherwise be possible.