I receive frequent emails about my platinum cure silicone posts (part 1, part 2). People all around the world want clarification of my process, so I’m happy to provide it.
I’ve been casting platinum cure silicone in SLA printed masters for over a year now for my keycap business, Cherry Festival, and have successfully done it hundreds of times with perfect accuracy in the finished mold. I’ve settled on a very strict but easy process to ensure it works every time.
Here’s what you do:
- Wash all excess resin from your part
It’s important to have a completely dry, clean part for this process. I wash my parts under a heavy stream of water, then place them into an ultrasonic bath of isopropyl alcohol, but you can use any method. Just make sure all uncured resin is cleaned off.
- Heat your part at 300F/150C for 2-3 minutes
This is half the secret. You’re looking for wisps of smoke. I use a toaster oven for this, but any heated chamber where smoke can escape will work. The moment I see wisps of smoke coming out of the door, I open it. As cold air rushes in, the part will smoke heavily. This is good! If you let it heat for too long, the part will develop cosmetic fractures. The perfect heating is right before these fractures would appear. Also, don’t breathe the smoke.
- UV cure your part normally
Don’t go overboard, just do it how you would normally do it. Extended UV curing does not make this process work any better.
- Tumble your part in Inhibit X for 5 minutes
I like to place the parts in a jar of Inhibit X inside a rock tumbler, but this probably works fine just swishing them around every few minutes by hand. You just want the Inhibit X to touch every surface and have enough time to get those surfaces fully reacted.
- Let your part dry
This happens pretty fast. Once the parts are dry, they’re ready for platinum cure silicone.
So long as your silicone is mixed well, the quality of the mold will be the same as any other non-SLA part. No gumminess, no lost detail.
I’d love to see what you make with this process! And please feel free to keep emailing–I’m always happy to answer any questions about this.
Do you find that you can re-use the residual jar of inhibit X liquid? How many uses do you get out of each batch? I want to try this method, it just seems cost prohibitive as the cheapest I can find inhibit X for is between $60-$70. Very helpful post, hopefully I’ll have a successful silicone mold soon!
2. Heat your part at 300F/150C for 2-3 minutes
For me, 150C in the oven caused instant cracks in the printed object (maybe it was too early right after it was printed?)
I prefer 70-80-90C steps for about 20 minutes each and no cracks
Thanks for sharing that! It could be a difference in the resin formulas we’re using.
I imagine this will vary with the resin formulation. I’m surprised yours cracked that fast!
Thanks for this info. I’m wondering if washing, curing and then coating with acrylic enamel will fix the part for casting. I’ve used Rustoleum 2x Acrylic Enamel spray on polyurethane foam (Renshape) with good results. I’d try myself but I;m trying to figure all of this out before purchasing the resin printer. I do have a resin SLA print from years ago. Not sure if the resin is similar at all…
Yes, very likely! I just couldn’t in my case because it would have messed up the tolerances. It had to be the exact part off the printer, and perfectly repeatable.
I used inhibitor x and my silicone stuck to the sla print parts