Under Pressure / by Alex Schreer

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Water is typically a forgiving compound, essential to humanity, and often a safe alternative to jump into, however with some influence from pressure it can be turned into something a bit more dangerous. Im talking about water jet cutting, the idea that by using a pump to force water through a small nozzle you will create a stream of water so powerful it will cut through just about any metal, glass, or other material. Add in a small amount of sand based cutting material and you will find yourself behind a machine capable of cutting inches thick worth of steel in a matter of minutes. 

Saturday was spent using a CNC (Computer Numerical Controlled) Water Jet cutter at Tech Shop in Chandler, AZ. A friend had received a rather large amount of aircraft grade aluminum from his work, the material had been considered obsolete by the company and we were glad to take it off their hands. Just one small issue, these sheets were 4ft x 12ft and weighed in at a couple hundreds pounds each. They needed to be sized down to a manageable size so we could run some parts on the CNC Mill, the water jet appointment was scheduled. Four U-haul locations later, a bunch of profanity, and one forklift later, we were loaded up and on our way to tech shop with enough aluminum to make a small Cesna, in tow.  

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A small program was written for the Mach 2 to cut a straight line, from that point forward we would load the metal sheet onto the bed, hand measure out our desired dimension and then coordinate between spotter and controller to align the cutting head. A click of the mouse would kick the pump on and begin running the program, but we were in for a long day of work. The 3/4 sheets of 6065 & 7075 aluminum would take about 10 minutes per cut and were were cutting them down into a mix of 12in and 16in segments. It took us a few runs before we really had the hang of things and could dial in our workflow. 

It was nice to have such a long period of time to work around this machine and pick up the little tricks of working efficiently. I learned how to managed your cutting head speed throughout the cut, enter your material at around 60% then ramp it up to 90%, accounting for any back spray with a decrease in speed. Slowing the cut near the end will ensure you fully separate the two pieces of material from each other. Each minute spent was a valuable lesson on a tool I can see myself using throughout my career.

It would take roughly 5 hours to make all the cuts we needed, followed by the long process of loading all this material back into the cars. It was bitter sweet, our hands had been constantly soaked in cold water from working around the bed, they were reminded by the chilly breeze that would pass through the space from time to time, and the our palms had been worked raw from the constant lifting of heavy yet thin material. In the end we accomplished our goal and there is now a stockpile of aluminum waiting to be turned into anything we can think of.