How a Water Jet Works

The energy required for cutting materials is obtained by pressurizing water to ultra-high pressures, and forming an intense cutting stream by focusing this high-speed water through a small, precious-diamond orifice There are two main steps involved in the waterjet cutting process. First, the ultra-high pressure pump or intensifier pressurizes normal tap water at pressure levels up to 60,000 psi (4,137 bar); to produce the energy required for cutting. Second, water is then focused through a small precious diamond orifice to form an intense cutting stream. The stream moves at a velocity of Mach 3, three times the speed of sound, depending on how the water pressure is exerted. The process is applicable to both water only and abrasive jets.

For abrasive cutting applications, abrasive garnet is fed into the abrasive mixing chamber, which is part of the cutting head body, to produce a coherent and an extremely energetic abrasive jet stream. Cutting harder materials requires adding a fine mesh abrasive to the cutting stream.

Various abrasive materials which can be used include olivine, garnet, and corundum with a particle size of between 50 to 120 mesh (0.2 to 0.5 mm). When abrasive is required, KMT Waterjet provides an abrasive unit consisting primarily of an abrasive hopper, an abrasive feeder system, a pneumatically controlled on/off valve, and the abrasive cutting nozzle which contains the specialized mixing chamber. The abrasive is first stored in the pressurized hopper and travels to a metering assembly, which controls the amount of particles fed to the nozzle. The abrasive is then introduced into the cutting stream in a special mixing chamber within the abrasive cutting head. Abrasive cutting allows harder materials to be cut at a faster rate by accelerating the erosion process. After the cut, residual energy from the cutting stream is dissipated in a catcher tank, which stores the kerf material and spent abrasive.

To achieve these pressures, water is introduced into the unit by way of a booster pump and filter. This filtering process is very important as water must be clean before reaching ultra-high pressures in order to protect the high pressure parts and provide a consistent cutting stream. A water treatment system is sometimes needed to remove harmful minerals from the water. After being filtered, the water enters the high pressure cylinder where it is pressurized to the desired level. The water is then carried to either an abrasive or straight-water cutting nozzle, depending on the application. The cutting nozzle can be stationary or integrated into motion equipment, which allows for intricate shapes and designs to be cut. Motion equipment can range from a simple cross-cutter to 2D systems and 3D machines as well as multiple axis robots. CAD/CAM software combined with CNC controllers translate drawings or commands into a digitally programmed path for the cutting head to follow.