What is plasma cutting?
How a plasma cutter works:
Basic plasma cutters use electricity to superheat air into plasma (the 4th state of matter), which is then blown through the metal to be cut. Plasma cutters require a compressed air supply and AC power to operate.
- Initially, the electrode is in contact with (touches) the nozzle.
- When the trigger is squeezed, DC current flows through this contact.
- Next, compressed air starts moving the electrode back and flows out the nozzle.
- A fixed gap is established between the electrode and the nozzle. (The power supply increases voltage in order to maintain a constant current through the joint.) Electrons arc though the gap, turning the air into plasma.
- Finally, the regulated DC current is switched so that it no longer flows to the nozzle but instead flows from the electrode to the work piece. Current and airflow continue until cutting is halted.
- The nozzle and electrode require periodic replacement. For this reason, they are called "consumables." Plasma cutters are only useful for cutting metal. Non-conductive materials like wood and plastic prevent the plasma cutter from doing step 5 above.
- The above steps describe the operation of a contact start plasma torch. Some older plasma torch designs use high voltage sparks to bridge the gap between a fixed electrode and nozzle when starting the arc. These high frequency/high voltage start units are generally not recommended for use with a computerized machine, because they cause severe electromagnetic interference.