Making a mold of a 3D print

I plan to make a mold of a custom toy i have printed. I wanted to know if people could point me in the right direction on the silicone molding material recommended for picking up the detail and the prep that needs to be done to the print. The toy is in parts (arms, torso, head, etc) that will then be re-assembled after casting.


Smooth On and Alumilite both sell silicones for molds. I think they both have tutorials as well.

You also might want to try soft polyurethane for the mold. It’s a lot cheaper and has a better shelf life from my experience.

You could reach out to @BJBenterprises. They have posted up some videos and have been a good resource for me.


I will second smooth-on.

Be prepared to spend some time (and materials) playing around before you get it right.

Out of curiosity, why not just print the mold on your Form2?

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Often it’s near impossible to print a mold straight away. Undercuts won’t work so it’s not so easy.

I’ve toyed with the idea of printing a mold directly in flexible but haven’t got around to it yet. It’s not as flexible as silicone but it should work for larger parts.

There are also cheaper soft urethanes that can be used for parts that are less complex.

Resurrecting this thread to see if anyone has had success with mold making. I’m using Smooth On’s Rebound 25 on a prints made from Black Resin and also Makerjuice SF Resin and THE SILICONE WILL NOT CURE. I’ve tried spray painting the models, but still no luck. Any tips on how to make a mold from a print?

I’m assuming you’re trying to use platinum cure silicone. Platinum cure has cure issues with many paints or resins. It’s a pain to work with on printed parts.

Unless you need to cast water clear parts from the mold try tin cure silicone. It has it’s own issues but it will cure.

You can also try soft polyurethane instead of silicone. I have madeseveral molds with polyurethane based resins. The print must be fully cured but it works even with painted parts. Use good mold release.

Yes, Smooth On’s Rebound 25 is a platinum silicone rubber. Had great results with it on many surfaces, but it refuses to cure on a printed part. What a pain having to clean the uncured goop off the parts. I’m trying to seal the parts in acrylic paint to see if that will enable the rubber to cure. RE mold release, are you using that to seal the master before applying the silicone?

I use tin cure silicone or polyurethane.

Tin cure is great for simple molds, but not for items with lots of undercuts. Rebound can even make glove mold that you can peal off. So I need to balance the strength with curing.

First make sure your part is clean, dry and not tacky. UV post cure under water will eliminate the tackiness.
I use Urethane Parafilm mold release from Price Driscoll. It will not leave any build up and works great with printed parts and tin or plat cure silicones.

Smooth On has their 200 series wax based release but it has a fairly long dry time 20-30 min and has a build up. That particular mold release is better suited for creating parting lines on rtv molds to keep the silicone layers from sticking to each other.