High pressure waterjet cutting

High pressure water jet cutting

The water is pressurized to a very high pressure, exceeding 50,000 psi. This pressurization is accomplished through the use of pumps of various designs, which will be discussed later in this chapter.

The high-pressure water is delivered to the cutting head through a series of stainless steel pipes. Depending on the material being cut, the cutting head can be a "pure water cutting head" or an "abrasive cutting head".

In the cutting head, high-pressure water is forced through a small diameter hole. The diameter of the orifice is between 0.004" and 0.020". This step converts the pressure of the water jet into velocity. We go from potential energy to kinetic energy. From the orifice, the water jet moves at a speed of 2200 mph or faster. Higher pressure leads to higher speed. A smaller diameter hole produces a faster water jet, but also produces a water stream with less kinetic energy because there is not so much water available to accelerate the abrasive particles to full speed.

In the pure water cutting head, the water leaves the cutting head immediately after passing through the orifice. The speed and power of the waterjet flow are sufficient to cut soft or thin materials, such as foam, rubber, cork, plastic, carpet, food, car roofs, circuit boards, etc.

In the abrasive cutting head, a very hard abrasive, usually garnet, is fed into the water jet. The abrasive particles are accelerated to approach the speed of the water jet. This gives the abrasive grains great strength. The abrasive water jet now passes down the abrasive nozzle or mixing tube, which is approximately 3 inches long and has an inner diameter between 0.030" and 0.050". The mixture of water and abrasive is discharged from the abrasive nozzle, which will cut hard materials such as metal, stone, acrylic, ceramics, composite materials, phenolic resin and porcelain.