Core77
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:
I’m a lapsed industrial designer. I was born in NYC and figured I’d die there, but a few years ago I abandoned New York to live on a farm in the countryside with my wife. We have six dogs.
Webinar
Create a Core77 Account
Already have an account? Sign In
By creating a Core77 account you confirm that you accept the Terms of Use
Please enter your email and we will send an email to reset your password.
3D Printing Ergonomic Knobs with a Resin Core
Take care when doing this - depending what epoxy you use the heat produced from curing can warm the printed part to where it begins to deform. It's happened to me!
I am using a urethane resin, it's get slightly warm but nowhere near hot enough to melt any plastic.
been using epoxy and urethane to backfill FDM parts for years. helps when you have a production line that uses large quantities of the stuff. The epoxy from EFI always sets smooth, and only bubbles are internal, which can be removed via vibes.
Aren't you making the bubbles "too small to see" instead of "squeezing them out"?
When I cast anything, the resin is always degassed in a vacuum tank first, then for additional strength and security I place the part in a pressure tank to crush any remaining bubbles. There are never really any left other the initial vacuum degassing. I find the parts are much stronger after being cured in a pressure tank. There are other advantages to the pressure tank as well as mine is temperature controllable. The parts come out looking like production injection molded parts. Absolutely, essential and fantastic if you are making working prototypes and simulated preproduction parts. The attached image is a SwingLink golf wearable product (soon to launch on Kickstarter) the part looks like a production part. You can't get that if you don't use the right process and equipment. I have other videos that show the process of of how to make silicone molds the right way too.
Thank you for that reply! Is the resin you use particularly slow setting? I ask because Rain linked to a video from Diresta a couple of months ago who explicitly stated that vacuum was a lot harder to use than overpressure (too slow to build up perhaps? Could be equipment related). Live and learn!
Marten, with very fast setting resins there is not enough time degas them properly. So, the only option is to put them under pressure. I don't use resins like that. There are lots of resins out there, I usually chose something with a minimum of 5-6 minutes to 15 min working time so I can use them correctly. You get much better results, patience....
Demonstrably more efficient: https://www.mcmaster.com/#machine-component-knobs
Possibly, but not really as cool or fun, as designing and using something of your own design.