Plasma Cutting Science

The Science of Plasma Cutting

It is important to understand how the system operates to avoid potential problems and to assist in diagnosing operational errors or failures.

Plasma cutting is a science as well as an art. To make good cuts it’s necessary to have a good understanding of your torch and materials, the right settings on your torch and CNC system, and consistent operation. While plasma cutting systems can run with constant height fixtures, warping of the materials or inaccurate fixturing can create variations in the distance from the torch tip to the material.

These variations can cause the kerf of the cut to change during the cut, or even for the torch to extinguish. The torch height controller gives you consistency in your torch height by maintaining the distance between the material and the torch tip.

Plasma Cutting Table

How Plasma Cutters Work

A plasma cutter creates an electrical arc between the torch tip and the material. This arc superheats the air and transforms it to plasma. It is this superheated plasma that cuts the material. It is necessary for the plasma cutter to maintain the electrical arc to continue to generate plasma.

Plasma cutters control the flow of current, which is the number of electrons per second, which come from the torch tip. The greater the current the more plasma is generated. To maintain the constant flow of electrons the torch voltage is varied. In basic electrical theory current=voltage/resistance. The torch has control of the voltage so what controls the resistance? It is a number of factors including the conductivity of the material being cut, the wear on the torch consumables, and the distance of the tip from the material.

The air between the torch and the material, acts as a resistor or insulator. The greater the air gap the greater the resistance and the larger the voltage which is needed to keep the constant current flow. Conversely the closer the torch tip is to the material the smaller the resistance the and the lower the voltage is. Assuming all other factors being constant, keeping the voltage constant will keep the distance from the material to the torch tip constant.