We’ve received quite a bit of email (and even some comments) requesting additional coverage of industrial tools and waterjet machining in particluar. So, we went looking for a friendly “waterjet expert” to introduce us (and you) to the technology.
Man, were we lucky. We found Carl Olsen. Carl works for OMAX, a manufacturer of high-end precision abrasive waterjet systems. But Carl’s waterjet experience goes way back. According to him, his father was one of the originators of the waterjet cutting concept back in the 1960’s, and while other kids played cowboys and indians, he ran around with the garden hose cutting up the yard playing “waterjet.”
For the last 10 years, he’s helped OMAX develop and improve the software that controls their cutting machines, but in his spare time he created and maintains http://www.waterjets.org/, a site chock full of myth-dispelling excucational facts about waterjet technology. Between all this, he took the time to talk to us.
One of the most common misconceptions about waterjets, according to Carl, is that they cut steel with water. Though early systems — circa 1970’s — cut with water alone, they weren’t capable of cutting anything as dense or hard as steel. Instead, those early machines were used more for cutting soft items like food and fabric. Modern waterjets are properly termed “abrasivejets” or “abrasive waterjets.”
Carl, from waterjets.com:
People often incorrectly use the word “waterjet” when they really mean “abrasivejet”. Also, people sometimes say “abrasivejet”, “abrasive waterjet”, or “AWJ”, which mean the same thing. Don’t worry. If you accidentally call an “abrasivejet” a “waterjet”. Nobody will laugh at you, as it is fairly common to do so. Likewise, their are multiple spellings for the terms “water-jet”, “waterjet”, “water jet”, etc. I’m not fully sure which is “proper”, so you will see that I use them all, depending on my mood.
Abrasivejets cut by using water to accelerate an abrasive material — which varies based on application, though garnet is common — through a very small nozzle, achieving very high pressures of 20,000 psi or more. As Carl says, think of a sand blaster; The sand does the work, not the air.
Modern abrasivejets can effectively cut metal up to 3″ or so, though as material thickness increases beyond 3″ the limiting factor is often time as opposed to machine capability. Again, Carl from waterjets.org:
If you want to cut steel that is thicker than 3″ (75mm), then you need to ask how long can you afford to wait for your part to be finished? The thicker the material, the longer the wait, and you just have to ask yourself if it is cost effective. Sometimes it is, but usually it is not. In the case of exotic materials where the material is extremely expensive and difficult to cut by other means, then 3″ (75mm) and thicker may be practical. Titanium is an example of such a material.
Carl indicated to us that often abrasivejet operators will perform thicker cuts on expensive materials like titanium because the waterjet’s small kerf — the material that’s destroyed in the cut — is very small in comparison to other cutting methods. Abrasivejet kerfs can run as small as .020″, though kerfs up to .060 are possible with many units.
Read on to page 2 for more from Carl and waterjets.org.
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