Molding SLA 3D prints with platinum-cured silicone
Advanced Guide to Platinum Molding 3D Prints
How to Mold a SLA 3D print
3D printing is getting cheaper and cheaper and more and more people have a 3D printer at home or in their studio. Although FDM printers are still prodomiately used because of their price range, several cheaper SLA printers have come on the market making SLA (resin) printing more common and more available than ever.
SLA and FDM
What's the difference? Well FDA printing uses a filament - a plastic wire on a spool - and melts this at high temperatures. The heated plastic is extruded through a nozzle and - by use of a movable rig - printed at a print bed. By printing layer upon layer the print is build up - a fraction of a mm at the time. Plastics can be of all sorts; PLA is popular so is ABS.
SLA printing is different as it uses a bath of UV activated resin on wich a laser or high-powered led is used to solidify the individual layers until the print is completed.
Everyone who ever tried to make a mold of a 3D printed SLA print ran into the same problems; INHIBITION! That is of course, if you used a PLATINUM cured silicone (or addition-cured silicone) for the mold. TIN cured silicones (or condesation-cured silicones) have no problem with SLA prints but platinums on the other hand... Major inhibition issues! In this blog I want to tackle some options to remedy this problem.
This article was largely based on the research of Joshua Woelke https://joshuawoehlke.com/ and I want to thank him very much for letting me use it for this write-up.
1. 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 with isopropyl alcohol, but you can use any method. Just make sure all uncured resin is cleaned off.
2. Heat your part at 300F/150C for 2-3 minutes
1. 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.
3. 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.
4. 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.
5. Let your part dry
This happens pretty fast. Once the parts are dry, they’re ready for platinum cure silicone.