Waterjet machining has been around for many years, but has traditionally been viewed as a specialty process with limited applications. However, recent advances are making waterjet machining practical for applications never before considered.

The waterjet cutting machine uses a stream of water and abrasive particles, such as garnet, to perform the cutting operation. The waterjet cutter takes city water (typically 80 psi), and through the use of an intensifier-type pump, pressurizes the water to 55,000 psi. When the abrasivejet cutting head is enabled, the water flows through a 0.010-inch diameter orifice into a mixing chamber. As the waterjet stream enters the mixing chamber, it creates a partial vacuum that draws the flow of abrasive particles through the abrasive delivery line. The abrasive particles combine with the waterjet stream to create the high energy abrasivejet cutting stream. This stream exits the cutting head at a velocity of up to 3,000 feet per second. Today's waterjet cutting machines are CNC controlled for accuracy, repeatability and ease of setup.

I recently visited Cutting Techniques Incorporated, in East Rutherford, New Jersey. The company's owner, Ron Radomski, has made a strong commitment to waterjet machining and it is now a major portion of his business. Mr. Radomski offered the following advantages of waterjet machining:

• Cuts through any substance. "I have yet to find a material that could not be cut by the waterjet process. I have used it to cut substances from paper to titanium." Mr. Radomski claims to have successfully cut Styrofoam, which typically can be cut only by hot knives or wires. Some of his company's waterjet cutting applications have included rubber gaskets, brass lettering, safety glass, marble tables, stainless steel panels, and even the old wooden floor of Madison Square Garden in New York City.
• Material yield is maximized. Parts can be nested very close to each other in order to maximize material utilization. In some cases, pieces can even share the same cutting line.
• No heat-affected zones. Mr. Radomski says that the waterjet process does not generate the same level of heat as other processes. As a result, the properties of the materials being cut do not change. The waterjet heat is concentrated so much that it literally dissipates into the chip or removed material. He adds that there will be no burn marks on parts that have been cut by the waterjet.
• No start hole is required. The waterjet nozzle is placed where the cutting is to begin. The waterjet burrows its own hole through the material, eliminating the need to drill the material beforehand.
• Burr-free edge quality. The waterjet cuts with very little force, so the amount of burr generated is either very small, or non-existent.
• Eliminates secondary operations. In many cases, the need for secondary operations, such as sawing, milling or drilling can be eliminated. Etching of numbers can be done during the waterjet process, eliminating the need for a separate etching operation. In addition, because the waterjet cuts without heat, there is no need to anneal the material after machining. "By cutting extremely fast, I have scored material and eliminated the need for a secondary press brake operation," says Mr. Radomski.

Dr. Earnest Geskin, a research professor at the New Jersey Institute of Technology in Newark, New Jersey, has experimented with waterjet machining for many years and has seen its versatility firsthand. Recently, Dr. Geskin shifted the focus of his research from material cutting to material cleaning. "There are some applications in which materials are just too hard to clean with conventional cleaning technologies," he says. "We have shown the waterjet cleaning process to be effective in these applications." By closely controlling the waterjet stream, unwanted materials can be removed without damaging the surface of the part being cleaned. The waterjet process is equally effective on large and small parts. Examples are control panels, surface plates, castings and forgings, and architectural materials.

If future advances in waterjet technology rival those of the past few years, waterjet usage will experience tremendous growth. If you have a challenging precision machining or parts cleaning application, you should consider the waterjet alternative.