Water jet cutting involves generating high pressures to force water through an orifice into a narrow, intense beam that can cut through a variety of materials. The nozzle, or orifice, typically used is made from a very hard mineral such as sapphire. However, more waterjets are using diamond as the orifice material to obtain better life and stream quality.
The Water Jet Process
high pressure water jetsA robust hydraulic pump is used to pressurize ordinary tap water to levels of 60,000 psi and more, depending on the pressure required for the material being cut. Creating water pressure depends on the ratio of the hydraulic piston to the water piston. For instance, a hydraulic intensifier with a 20 times ratio of hydraulic piston to water piston and operating at 3,000 psi oil will produce 60,000 psi water for cutting.
When needed, the pressurized water is released through tubing to pass through the orifice as a fine cutting stream. The water stream may be as thin as a human hair but moving at speeds of more than 2,000 mph to create a powerful cutting stream.
The pressure required also varies by material. Wood can generally be cut easily at 38,000 psi; hard plastics at up to 55,000 psi, and very hard materials like steel or granite will require pressures of up to 90,000 psi or more. However, cutting harder materials also normally requires the use of abrasive jets.
This includes feeding an abrasive material into a mixing chamber just below the waterjet orifice. The mixing chamber is normally positioned on the cutting head body. The abrasive is then accelerated by the waterjet stream to become an abrasive jet.
The abrasive is usually finely ground from a hard mineral, but may also be common rock or sand, depending on the intended use. The hardness of various materials is well known through their rating on the Mohs scale.
This depends on the system (horsepower at the cutting point) and the psi produced. It also depends on the technology of the water jet. Cutting shapes out of steel a half-inch in thickness normally takes about 12 seconds per inch. Cutting quarter-inch aluminum may proceed at more than 1 inch per second. In both cases, this process is still fast compared to saws, and much more precise than torch cutting.
Modern high-pressure water jets typically use between one-half and one full U.S. gallon of water per minute. The water is recycled through a closed-loop system. Filtration is used to ensure no impurities in the water, which could create blockages and interfere with a consistent cutting stream.
At APW WaterJet we are proud of our commitment to innovation and customer support. We are constantly striving for improvement to our products and services. If you have any questions on choosing the right water jet system, contact us today.