A water jet cutter, also known as a water jet or water jet, is an industrial tool capable of cutting a wide variety of materials using a very 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 abrasive to cut hard materials such as metal or granite, while the terms pure water jet and water-only cutting refer to water jet cutting without the use of added abrasives, often used for softer materials such as wood or rubber.
Water jet cutting is often used during fabrication of machine parts. It is the preferred method when the materials being cut are sensitive to the high temperatures generated by other methods. Water jet cutting is used in various industries, including mining and aerospace, for cutting, shaping, and reaming.
There are six main process characteristics to water jet cutting:
1. Uses a high velocity stream of abrasive particles suspended in a stream of Ultra High Pressure Water (30,000–90,000 psi) which is produced by a water jet intensifier pump.
2. Is used for machining a large array of materials, including heat-sensitive, delicate or very hard materials.
3. Produces no heat damage to work piece surface or edges.
4. Nozzles are typically made of sintered boride.
5. Produces a taper of less than 1 degree on most cuts, which can be reduced or eliminated entirely by slowing down the cut process.
6. Distance of nozzle from work piece affects the size of the kerf and the removal rate of material. Typical distance is .125″ (3.175 mm).
Temperature is not as much of a factor.
Commercial water jet cutting systems are available from manufacturers all over the world, in a range of sizes, and with water pumps capable of a range of pressures. Typical water jet cutting machines have a working envelope as small as a few square feet, or up to hundreds of square feet. Ultra-high-pressure water pumps are available from as low as 40,000 psi (276 MPa) up to 100,000 psi (689 MPa)
Water jet control
As water jet cutting moved into traditional manufacturing shops, controlling the cutter reliably and accurately was essential. Early water jet cutting systems adapted traditional systems such as mechanical pantographs and CNC systems based on John Parsons’ 1952 NC milling machine and running G-code. Challenges inherent to water jet technology revealed the inadequacies of traditional G-Code, as accuracy depends on varying the speed of the nozzle as it approaches corners and details. Creating motion control systems to incorporate those variables became a major innovation for leading water jet manufacturers in the early 1990s, with Dr. John Olsen of OMAX Corporation developing systems to precisely position the water jet nozzle while accurately specifying the speed at every point along the path, and also utilizing common PCs as a controller. The largest water jet manufacturer, Flow International (a spinoff of Flow Industries), recognized the benefits of that system and licensed the OMAX software, with the result that the vast majority of water jet cutting machines worldwide are simple to use, fast, and accurate.
An important benefit of the water jet is the ability to cut material without interfering with its inherent structure, as there is no "heat-affected zone" (HAZ). Minimizing the effects of heat allows metals to be cut without harming or changing intrinsic properties.
Water jet cutters are also capable of producing intricate cuts in material. With specialized software and 3-D machining heads, complex shapes can be produced.
The kerf, or width, of the cut can be adjusted by swapping parts in the nozzle, as well as changing the type and size of abrasive. Typical abrasive cuts have a kerf in the range of 0.04″ to 0.05″ (1.016 to 1.27 mm), but can be as narrow as 0.02″ (0.508 mm). Non-abrasive cuts are normally 0.007″ to 0.013″ (0.178 to 0.33 mm), but can be as small as 0.003″ (0.076 mm), which is approximately that of a human hair. These small jets can permit small details in a wide range of applications.
Water jets are capable of attaining accuracies down to 0.005″ (0.13 mm) and repeat abilities down to 0.001″ (0.025 mm).
Due to its relatively narrow kerf, water jet cutting can reduce the amount of scrap material produced, by allowing uncut parts to be nested more closely together than traditional cutting methods. Water jets use approximately one half to one gallon (2 to 4 liters) per minute (depending on the cutting head's orifice size), and the water can be recycled using a closed-loop system. Waste water usually is clean enough to filter and dispose of down a drain. The garnet abrasive is a non-toxic material that can be recycled for repeated use; otherwise, it can usually be disposed in a landfill. Water jets also produce fewer airborne dust particles, smoke, fumes, and contaminants, reducing operator exposure to hazardous materials.