Since the water-injection plasma-arc process was introduced in 1970, plasma-arc cutting has been increasingly used for mild steel. The water, which is injected radially into the nozzle around the arc, restricts the size of the arc and improves the quality of the cut. This technique was developed by the Hypertherm Corporation (of U.S.A.); the company's products are marketed in the U.K. by BOC, who also fit Hypertherm nozzle systems on several of their own cutting machines. The article describes and discusses the water-injection plasma-arc cutting process and its capabilities, and includes brief information on some competitive processes (the "dual flow" technique, air cutting, and "water shield"). Despite the advantages of plasma-arc cutting, any decision to introduce it requires careful consideration. The high cutting-speeds (e.g., 2.5 m a minute for 12-mm mild steel) entail substantial electrical power (perhaps about 220 kW), with supply arrangements to correspond. The type of work is also important; the process is best suited to large batch, heavy gauge production. Retro-fitting to existing oxy-gas cutting machines is possible if they can cope with the increased speeds and handling capacity. Hybrid machines (e.g., with four oxy-gas cutters and one plasma-arc nozzle) have also been developed. Some information is included on BOC's recently-introduced Falcon S cutting machine, which can be supplied either as a conventional oxy-gas machine or as a plasma-arc system using "dry" cutting for plate up to 60 mm thickness and water-injection for plate up to 150 mm. The water-injection equipment can also be used for (factory) underwater cutting, in a machine-mounted tank, to reduce noise and fume problems. This machine is designed to take a new low-cost numerical-control system being developed in conjunction with Kongsberg.

  • Corporate Authors:

    Institution of Production Engineers

    Rochester House, 66 Little Ealing Lane
    London W5 4XX,   England 
  • Publication Date: 1980-11

Media Info

  • Pagination: p. 17
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00331578
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: May 21 1981 12:00AM