This month's Make magazine features an out-of-the-box development: a waterjet cutter for a couple of hundred bucks. The Wazer is a $4500 machine. Author Ben Krasnow looked around at what he could easily get and started figuring out how to create a waterjet cutter.
Ben does something truly noteworthy. He creates a usable waterjet cutter, capable of cutting through metal, wood, and other material. He accomplishes this using a rig he put together for only a few hundred dollars. The heart of the system is a Sun Joe pressure washer that he bought for $150 on Amazon.Without buying the magazine, the best source of information on how to replicate his cutter is his 22 minute long video on YouTube. Information on sources and how to get everything is in the "Show More" tab on YouTube, so you need to go there for that information, but he got most of these parts from two places: AccuStream (a waterjet parts supplier) and McMaster-Carr.
Ben’s cobbled-together rig might not look like much, but it does get the job done. In the video, you see him cutting through 1/16″ aluminum (at ~2″/min with .4 lbs/min of abrasive @3200psi), 1/8″ aluminum (at about 1/2 the cutting speed, abrasive and psi values the same), 3/8″ hardwood, styrofoam (in water-only/no abrasive mode), and bread (yes, bread).He cuts the styrofoam and bread with only water, but water isn't very useful for cutting. The agent used is coarse garnet abrasive grains, and the purpose of the water is to accelerate the abrasive to speeds that allow it to work. It also probably cools the work area, too. Garnet is a moderately hard stone that has historically been used as an abrasive - you can still buy garnet paper. It's a non-toxic, safe abrasive, just a harder version of the silicon dioxide sand in sandpaper. The source he links to sells it at about 50cents/lb, so when you look at the 0.4 lbs/minute cuts they describe, you can think 20 cents/minute to cut the aluminum he demonstrated.
For the abrasives hopper, after doing research into commercial hoppers, he realized that they’re basically just a gravity-fed tub with a hole in the bottom (and a means of adjusting the amount of abrasive). So, he made his own.Now, cool as it is to develop a usable waterjet cutter that can cost the builder under $500, I'm not sure where this fits in. The attraction of a waterjet is that it cuts materials that are difficult to precisely machine: things like carbon fiber or fiberglass laid up panels, or glass. Industrially, they're also used to cut steel and other hard metals, not just the aluminum he cuts. I don't think this one has the horsepower to cut harder metals. Cutting freehand is probably not any more dangerous than cutting with a moving saw blade. Water at the pressures he's talking about will cut off a finger just as easily as a saw. At the very end of the video, he suggests turning it into something like a CNC machine that moves the work into the waterjet, something like the way large X/Y Plotters roll paper under the pen, or some wood carving machines will roll a board back and forth while the carving tool moves in the other two axes.