Gas metal arc cutting (GMAC) is when metals are cut by the heat of an arc between a continuous filler metal electrode and the work-piece, with externally supplied shielding gas.
Gas metal arc cutting (GMAC) uses the GMAW welding machine to achieve burnthrough, but this is not a common AC process.
The electric current is supplied by a variable transformer, through heavy electrical leads. One lead is connected to the electrode and the other is connected to the metal being cut. The electrode is then held close to the metal so that an electric arc can move from the electrode to the metal, completing the circuit.
- Michigan Department of Energy, Labor & Economic Growth