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re[PSUBS-MAILIST] Aqua jet cutting acrylic

Thijs,
 
Your very right in that aqua jet cutting leaves a tapered cut that is some times noticeable on thinker materials. On some metals it can be more so then some composite materials I've seen cut. My local aqua jet company has done rough cuts up to 7" thick on pieces of titanium for a US Navy reactor part, that was later machined into a precision part.
 
Acrylic is generally very easy and fast to cut on a good aqua jet machine, with a good pressure rating, leaving you only a very small tapper in a 1.25" piece of acrylic. For thicker acrylic I'll have to find out how much of a tapper you will get, since the machine has to run slower to cut through it. Also the programmer can tell the machine to cut at different rates and so for some applications you can get a very smooth cut on the edge, like we generally want on a view-port, unless one plans to machine the acrylic afterwards.  For that, your basically using the aqua jet cutter to rough cut your view-ports over size for you.
 
Since one usually has a large FOS (factor of safety) in there viewport design, a slightly conical viewport shouldn't be a problem if you put the smaller outside diameter side of the viewport to the outside and just fill in the small gap with silicone.


Regards,
Brent Hartwig


From: thijs-struijs@planet.nl
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Aqua jet cutting acrylic
Date: Wed, 22 Aug 2007 22:32:31 +0200

Hello,
 
There is a small problem with aqua jet cutting. It is difficult to explain for me as a Dutchman in English but a water jet (even with abrasive additives) tends to act as a bullit. At the entrance it cuts a small hole, at the other end there is a "big" gab. Cutting thin materials is no problem but as soon as it gets thicker the jet makes a connical hole. When you cut a round viewport you will end up with a slightly connical one. This requires machining afterwards to meet the neccessary tolerances. 
 
Regards,
Thijs Struijs