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An evaluation of a high tolerance plasma arc cutting (HTPAC) process


TWI Industrial Member Report Summary 558/1996

D Howse

In order to improve upon conventional plasma cutting processes, high tolerance plasma arc cutting (HTPAC) processes have recently been developed. A common feature of these processes is that the primary plasma gas is further constricted downstream of the nozzle.

For the particular system used in this report, the constriction is achieved by a secondary flow of gas. Alternatively, the arc can be stabilised by means of a rotating magnetic field which maintains the rotation initiated by the swirling gas without the need for a secondary shielding gas. Both techniques result in a constricted plasma column with an arc current density of two to three times that of conventional plasma.

One commercially available HTPAC process is the Hydefinition HD-1070 plasma system produced by Hypertherm, which constricts the plasma arc with a secondary gas flow. This process and a conventional dual gas plasma were evaluated in terms of cut edge quality, according to DIN 231 0, and productivity at TWI and the results were compared with laser and oxy-fuel processes. The data used for comparison were obtained from samples produced by commercial jobbing shops using commercial practice rather than under laboratory conditions.


  • To assess the potential of the HTPAC process for cutting mild steel, stainless steel and aluminium.
  • To compare the performance of the HTPAC plasma process with competing processes such as CO2 and Nd:YAG laser, conventional dual gas plasma and oxy-fuel systems.

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