If you're making something for yourself and casting it in resin, you can probably live with the inevitable air bubbles that appear in the object. But if you're an industrial designer prototyping something a client's going to see, bubbles are a no-no. That's why professional prototypers like Eric Strebel use pressure casting. That's when you do the casting inside a pressure tank, hooking it up to a compressor and setting the interior at 60 p.s.i. or so, which'll squeeze those bubbles out of the resin.
Some pain points for Strebel are the lousy wingnut-handled screws on his pressure tank's clamps. So here he shows you how he whips up some more ergonomic knobs using 3D printing, urethane resin and the original clamp screws: