Water is pressurized to very high pressures, in excess of 50,000 psi. This pressurization is accomplished with the use of pumps of various designs, discussed next in this chapter.

The high pressure water is transported through a series of stainless steel tubes to a cutting head. Depending upon the material being cut, the cutting head can be either a "pure water cutting head" or an "abrasive cutting head."

In the cutting head, the high pressure water is forced through a small diameter orifice. The diameter of this orifice is anywhere from 0.004" to 0.020". This step converts the pressure of the waterjet stream into speed. We go from potential energy to kinetic energy. Coming out of the orifice, the waterjet stream is moving at 2200 mph or faster. Higher pressure results in higher speed. Smaller diameter orifices yield a faster waterjet stream, but also a stream with less kinetic energy since there is not as much water available to accelerate abrasive grains to full speed.

In a pure water cutting head, the water immediately exits the cutting head after passing through the orifice. The speed and power of the waterjet stream is enough to cut soft or thin materials like foam, rubber, soft wood, plastics, carpet, food, car headliners, circuit boards and more.

In an abrasive cutting head, a very hard abrasive, typically garnet, is fed into the waterjet stream. The abrasive particles are accelerated to near the speed of the waterjet stream. This gives the abrasive particles much power. The abrasive waterjet stream now travels down through an abrasive nozzle, or mixing tube, approximately 3 inches long with an inner diameter of between .030" and 0.050". The mixture of water and abrasive exits the abrasive nozzle and will cut hard materials like metals, stone, acrylic, ceramic, composites, phenolics and porcelain.

A CNC control will move the cutting head in up to 6 axes of motion to cut the targeted work piece.