A water jet cutter, also known as a water jet or waterjet, is an industrial tool capable of cutting a wide variety of materials using an extremely high-pressure jet of water, or a mixture of water and an abrasive substance. The term abrasive jet refers specifically to the use of a mixture of water and an abrasive to cut hard materials such as metal, stone or glass, while the terms pure waterjet and water-only cutting refer to waterjet cutting without the use of added abrasives, often used for softer materials such as wood or rubber.

Waterjet cutting is often used during the fabrication of machine parts. It is the preferred method when the materials being cut are sensitive to the high temperatures generated by other methods; examples of such materials include plastic and aluminium. Waterjet cutting is used in various industries, including mining and aerospace, for cutting, shaping, and reaming.

History

Waterjet

While using high-pressure water for erosion dates back as far as the mid-1800s with hydraulic mining, it was not until the 1930s that narrow jets of water started to appear as an industrial cutting device. In 1933, the Paper Patents Company in Wisconsin developed a paper metering, cutting, and reeling machine that used a diagonally moving waterjet nozzle to cut a horizontally moving sheet of continuous paper.Fourness, Charles A et al, Paper Metering, Cutting, and Reeling, filed 22 May 1933, and issued 2 July 1935. These early applications were at low pressure and restricted to soft materials like paper.

Waterjet technology evolved in the post-war era as researchers around the world searched for new methods of efficient cutting systems. In 1956, Carl Johnson of Durox International in Luxembourg developed a method for cutting plastic shapes using a thin stream high-pressure water jet, but those materials, like paper, were soft materials.Johnson, Carl Olof, Method for Cutting Up Plastic and Semi-Plastic Masses, filed 13 March 1956, and issued 14 April 1959. In 1958, Billie Schwacha of North American Aviation developed a system using ultra-high-pressure liquid to cut hard materials.Schwacha, Billie G., Liquid Cutting of Hard Metals, filed 13 October 1958, and issued 23 May 1961. This system used a pump to deliver a hypersonic liquid jet that could cut high-strength alloys such as PH15-7-MO stainless steel. Used to cut honeycomb laminate for the Mach 3 North American XB-70 Valkyrie, this cutting method resulted in delaminating at high speed, requiring changes to the manufacturing process.Jenkins, Dennis R & Tony R Landis, Valkyrie: North American's Mach 3 Superbomber, Specialty Press, 2004, p. 108.

While not effective for the XB-70 project, the concept was valid and further research continued to evolve waterjet cutting. In 1962, Philip Rice of Union Carbide explored using a pulsing waterjet at up to to cut metals, stone, and other materials.Rice, Phillip K., Process for Cutting and Working Solid Materials, filed 26 October 1962, and issued 19 October 1965. Research by S.J. Leach and G.L. Walker in the mid-1960s expanded on traditional coal waterjet cutting to determine the ideal nozzle shape for high-pressure waterjet cutting of stone,Leach, S.J. and G.L. Walker, The Application of High Speed Liquid Jets to Cutting, Philosophical Transactions of the Royal Society of London, Series A, Mathematical and Physical Sciences, Vol 260, No 1110, 28 July 1966, pp. 295–310. and Norman Franz in the late 1960s focused on waterjet cutting of soft materials by dissolving long-chain polymers in the water to improve the cohesiveness of the jet stream.Franz, Norman C., High Velocity Liquid Jet, filed 31 May 1968, and issued 18 August 1970. In the early 1970s, the desire to improve the durability of the waterjet nozzle led Ray Chadwick, Michael Kurko, and Joseph Corriveau of the Bendix Corporation to come up with the idea of using corundum crystal to form a waterjet orifice,Chadwick, Ray F Chadwick, Michael C Kurko, and Joseph A Corriveau, Nozzle for Producing Fluid Cutting Jet, filed 1 March 1971, and issued 4 September 1973. while Norman Franz expanded on this and created a waterjet nozzle with an orifice as small as that operated at pressures up to .Franz, Norman C., Very High Velocity Fluid Jet Nozzles and Methods of Making Same, filed 16 July 1971, and issued 7 August 1973. John Olsen, along with George Hurlburt and Louis Kapcsandy at Flow Research (later Flow Industries), further improved the commercial potential of the water jet by showing that treating the water beforehand could increase the operational life of the nozzle.Olsen, John H., George H. Hurlburt, and Louis E. Kapcsandy, Method for Making High Velocity Liquid Jet, filed 21 June 1976, and issued 12 August 1980.

High pressure

High-pressure vessels and pumps became affordable and reliable with the advent of steam power. By the mid-1800s, steam locomotives were common and the first efficient steam-driven fire engine was operational. By the turn of the century, high-pressure reliability improved, with locomotive research leading to a sixfold increase in boiler pressure, some reaching . Most high-pressure pumps at this time, though, operated around .

High-pressure systems were further shaped by the aviation, automotive, and oil industries. Aircraft manufacturers such as Boeing developed seals for hydraulically boosted control systems in the 1940s,Berry, Mitchell M., Piston Sealing Assembly, filed 3 March 1941, and issued 23 March 1943. while automotive designers followed similar research for hydraulic suspension systems.Templeton, Herbert W., Metering Valve Seal, filed 11 July 1958, and issued 18 July 1961. Higher pressures in hydraulic systems in the oil industry also led to the development of advanced seals and packing to prevent leaks.Webb, Derrel D., High Pressure Packing Means, filed 12 August 1957, and issued 17 October 1961.

These advances in seal technology, plus the rise of plastics in the post-war years, led to the development of the first reliable high-pressure pump. The invention of Marlex by Robert Banks and John Paul Hogan of the Phillips Petroleum Company required a catalyst to be injected into the polyethylene.Hogan, John Paul and Robert L. Banks, Polymers and Production Thereof, filed 26 March 1956, and issued 4 March 1958. McCartney Manufacturing Company in Baxter Springs, Kansas, began manufacturing these high-pressure pumps in 1960 for the polyethylene industry. Flow Industries in Kent, Washington set the groundwork for commercial viability of waterjets with John Olsen's development of the high-pressure fluid intensifier in 1973,Olsen, John H., High Pressure Fluid Intensifier and Method, filed 12 January 1973, and issued 21 May 1974. a design that was further refined in 1976.Olsen, John H., High Pressure Fluid Intensifier and Method, filed 16 March 1976, and issued 14 June 1977. Flow Industries then combined the high-pressure pump research with their waterjet nozzle research and brought waterjet cutting into the manufacturing world.

Abrasive waterjet

While cutting with water is possible for soft materials, adding an abrasive turned the water jet into a modern machining tool for all materials. This began in 1935 when the idea of adding an abrasive to the water stream was developed by Elmo Smith for liquid abrasive blasting.Smith, Elmo V., Liquid Blasting, filed 10 June 1935, and issued 12 May 1936. Smith's design was further refined by Leslie Tirrell of the Hydroblast Corporation in 1937, resulting in a nozzle design that created a mix of high-pressure water and abrasive for the purpose of wet blasting.Tirrell, Leslie L., Sandblast Device, filed 3 April 1937, and issued 17 October 1939.

Today, there are two different types of Abrasive Waterjets:

Abrasive water suspension jet (AWSJ) cutting The abrasive water suspension jet (AWSJ) – often called “slurry jet” or “water abrasive suspension (WAS) jet” – is a specific type of abrasive water jet, which is used for waterjet cutting. In contrast to the abrasive water injector jet (AWIJ), the abrasive water suspension jet (AWSJ) is characterised by the fact that the mixing of abrasive and water takes place before the nozzle. This has the effect that, in contrast to AWIJ, the jet consists of only two components: the water and the abrasive.

Since there are only 2 components (water and abrasive) in the AWSJ, the acceleration of the abrasive grains by the water takes place with a significantly increased efficiency compared to the AWIJ. The abrasive grains become faster with the WASS than with the WAIS for the same hydraulic power of the system. Therefore, comparatively deeper or faster cuts can be made with the AWSJ.

AWSJ cutting, in contrast to the AWIJ cutting process described below, can also be used for mobile cutting applications and cutting underwater, in addition to machining demanding materials. Examples include bomb disposal, as well as the dismantling of offshore installations or the dismantling of reactor pressure vessel installations in nuclear power plants.

Abrasive Water Injector Jet (AWIJ) cutting

The AWIJ is generated by a water jet that passes through a mixing chamber (a cavity) after exiting the water nozzle and enters a focusing tube at the exit of the mixing chamber. The interaction of the water jet in the mixing chamber with the air inside creates negative pressure, the water jet entrains air particles. This negative pressure is used for the pneumatic transport of the abrasive into the chamber (the abrasive is led to a lateral opening (bore) of the mixing chamber by means of a hose).

After contact with the abrasive material in the mixing chamber with the water jet, the individual abrasive grains are accelerated and entrained in the direction of the focusing tube. The air used as a carrier medium for transporting the abrasive into the mixing chamber also becomes part of the AWIJ, which now consists of three components (water – abrasive – air). In the focusing tube, which is (should be) optimised in its length for this purpose, the abrasive is further accelerated (energy transfer from the water to the abrasive grain) and the AWIJ ideally leaves the focusing tube at the maximum possible abrasive grain speed.

Waterjet control

As waterjet cutting moved into traditional manufacturing shops, controlling the cutter reliably and accurately was essential. Early waterjet cutting systems adapted traditional systems such as and CNC systems based on John Parsons' 1952 NC milling machine and running G-code. Challenges inherent to waterjet technology revealed the inadequacies of traditional G-Code. The accuracy depends on varying the speed of the nozzle as it approaches corners and details. A major breakthrough came in the early '90s, when John Olsen developed systems to precisely position the waterjet nozzle while accurately specifying the speed at every point along the path and using common PCs as a controller.

Operation