What we know and what we do not know about plasma arc cutting

After a brief history of plasma arc cutting (PAC) is given, its types and abilities are discussed. Experimental data (unfortunately, little is available) on plasma parameters are reviewed. The status of contemporary understanding of the process involved in PAC is presented. The main emphasis is on those processes that determine the technological abilities of the method. Along with the existing theories reviewed, we propose qualitative hypotheses on some of these processes. Among them are: dependence of the cyclic cathode erosion on the rate of current increase, double arcing and the role of insulating inclusions at the nozzle orifice on double arcing, dross formation and the shape of the kerf.