Water Injection Plasma

(c) Water injection plasma cutting.

This modification of the PAC process uses a symmetrical impinging water jet near the constricting nozzle orifice to further constrict the plasma flame.

The arrangement is shown in figure 10-74.

The end of the nozzle can be made of ceramic, which helps to prevent double arcing.

The water constricted plasma produces a narrow, sharply defined cut at speeds above those of conventional PAC.

Because most of the water leaves the nozzle as a liquid spray, it cools the kerf edge, producing a sharp corner.

The kerf is clean.

When the orifice gas and water are injected in tangent, the plasma gas swirls as it emerges from the nozzle and water jet.

This can produce a high quality perpendicular face on one side of the kerf.

The other side of the kerf is beveled.

In shape cutting applications, the direction of travel must be selected to produce a perpendicular cut on the part and the bevel cut on the scrap.