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Greetings SMMOM's, I've been having way to much fun lately, welding, carbon arc cutting, making a 45 degree angle sandblasting head for blasting the back sides of support ribs, and so on. More on those later. My friend that owns a water jet cutting business and I wanted to test cut some thick acrylic. So what better to cut then my old 2" thick 16" OD forward viewport. How else was I to remove the yellow paint from it. ;} I applied some clear packing tape to the outer areas, enough to have plenty on both sides of the cut to protect the front and back viewing surfaces from the garnet cutting material and hold on the plastic in the middle. Then we made a sliver test cut at a rate of 2 inches per minute. It looked quite good, and you can see in the pictures the drag angle as it was being cut. No heat could be felt on the cut surfaces. This doesn't mean the acrylic shouldn't be annealed after aqua jet cutting. But perhaps some day there will be some testing in that area we can bank on. The first test cut was pretty smooth. But we wanted to see if we could get it even smoother, so the main cutting pass to make the acrylic have a OD of 15" was done at a rate of 1.5 inches per minute. It can out ver smooth. I don't think you would need to do any lathe turning afterwards. The acrylic was supported by two sheets of sheet rock on top of steel grating. We only had grating on the the outer edge, so to keep the part from tipping at the end we installed straws to hold it together. If the jet hits the edge of a new grate, it will splash back and damage the acrylic. So it was good we had old worn out grates. But we should of added one grate in them middle. Since the window tipped up at the last but, and made a small angled cut we didn't want. That's why testing is good, right. http://cid-5085d10eb6afe47c.skydrive.live.com/browse.aspx/Water%20Jet%20Cutting%20Thick%20Acrylic The cut turned out really nice, and was ever smoother wave wise then the inch think acrylic viewport I have that was cut with a CNC Laser for a hyperbaric chamber. ( Note I don't know what the lasers cut rate was, or how powerful of one it was) The laser cut surface is glossy, and the aqua jet cut surface looks like it's been media blasted with baking soda. The surface created by the aqua jet cutting is much better for bonding the Seka Primer to. I don't know if the melting damage done to acrylic from the laser can be properly annealed for submarine use? Next time we might just drill a start hole on the outer waste part of the window or ease into the cut and ease out of the cut with out removing the last little bit at the end of the cut. Then just sand that part off. But I think we should be able to support it perfectly, and make sure the stepper motors are working correctly and do it all in one go. The cost for having one 2" acrylic viewport that is 16" OD cut by Brendon is $90 if your just having one cut. I might just order up a whole 4' by 8' sheet of cast acrylic and have him cut up a number of viewports at once to bring the cost down per part and make them available to the group. For just rough cutting out a viewport that will later be machined on a lathe for a conical fustrum or what have you, the cut rate can be much faster, and so the cost will be lower. Regards, Szybowski |