Making Plastic Framing

     One of the smaller tasks that I need to take care of for the initial construction is making a frame to hold everything in place inside the pressure hull. The ROV is going to enclose all the electronics inside a single pressure vessel and I'm going to use laser cut plastic sheets to hold it all in place. The frame has to accomplish several things:
-Hold all electronics in place without shorting or grounding anything
-Rigidly mount the camera/servo and their linkage
-Route cooling airflow
And, of course, it needs to make everything as small and compact as possible. I want the frame to be repairable, upgradable, etc., so I can't use adhesives and I can't melt the pieces together. No permanent connections. I'll be able to fit some pieces together with simple finger joints, but other parts will require a more rigid connection. For this I decided to make some sort of snap-in clip.

     I started out using 1/8" acrylic and it was pretty easy to make simple rectangular tabs that fit into rectangular slots with little more than friction to hold them in place. However, 1/8" acrylic is thicker and heavier than what I need, so switched to 1/16". The rectangular tabs didn't work as well with this thickness, so I decided to use clip buckles instead.

I drew up a few designs so I could cut some test pieces. After a lot of trial and error, I came up with dimensions that fit beautifully. However, the acrylic wasn't doing so well. It's too hard and brittle to form tabs that flex and bend repeatedly. Some clips lasted half a dozen bends before breaking, and some lasted zero. I took the same drawings and cut them out of delrin, which is much more flexible, and they worked perfectly.

     So here's my final product, delrin clips that pop nicely into place and are removable/replacable. On the right you can see the square tabs cut from 1/8" acrylic. On the left are the 1/16" acrylic (clear) and delrin (white) tabs. For the final parts I'll probably cut the base plate with finger joints and slots out of acrylic and the tabbed parts out of delrin. That should work nicely. I've posted the Solidworks and .DWG drawings for the clips below.