How Does a Water Jet Cutter Work?

The Basics

Water jet cutters (waterjets) are powerful industrial machines that use highly pressurized streams of water to help produce everything from disposable diapers, tissue paper and candy bars to finely detailed exotic metal components. To do their job, water jet cutters rely on a mixture of technologies, each working in close tandem to create machines of remarkable accuracy and reliability.

Water jet cutters come in two basic forms. Pure waterjets, operating at pressures from 20,000 to 60,000 pounds per square inch (psi), use water only, and are limited to cutting softer materials like foam, paper and rubber. Abrasive waterjets, which operate from 60,000 to nearly 90,000 psi, use added abrasive material (commonly crushed garnet stone) to produce greatly increased cutting force. Although similar in most respects, cutters designed for one task are not suitable for the other.

Pumps

Waterjets generate cutting pressure from one of two types of water pump. Direct drive pumps work on the same principles as household pressure washers, using a series of plungers to generate heightened pressure. Intensifier pumps are more sophisticated, using a hydraulic pressure system along with a separate system to stabilize water flow. Intensifiers are 10 to 25 percent stronger the direct drive pumps, and are now the de facto industry standard.

Cutting Heads

High-pressure water from the pump is passed through a series of conduits to the cutting head. Here, it exits in a controlled stream through a tiny opening called a jewel, or orifice. Orifices are typically made from diamond, ruby or sapphire to withstand the enormous pressure. Even so, they must be periodically replaced to ensure proper operation. In abrasive water jet cutters, there is a small chamber beyond the orifice where crushed stone is vacuum-fed into the pressurized stream. Water's main function here is to propel these stone particles, which do the actual cutting. The most powerful water jet cutters combine abrasion with a moving cutting head.

Water speeds generated by modern cutting heads typically approach the speed of sound (750 miles per hour), and some advanced cutters produce speeds nearing 1750 miles per hour. Streams of this force can cut even the hardest materials.

Some water jet cutters use stationary heads. Typically, stationary cutters perform jobs similar to traditional cutting equipment, with material fed through the machines by human or machine operators. Motion cutters hold or turn material in place while it is worked on by a moving head.

The simplest and most common motion cutters are flatstock machines, which are used to cut flat materials on two axes. Like almost all motion waterjets, they are computer-controlled. Typically, a programmer uses computer software to create a design. Specifications for that design are then fed into the cutter, which precisely replicates the needed part. Far more complex results are gained from five-axis machines, which can manipulate parts in three-dimensional space and cut them at virtually any angle.

References

• Waterjets.org
• Flow Corporation

Resources

• Read this Article in Spanish