Silicone mold from grey v3

Do you have problems making silicone moulds from grey v3 resin?
My molds sometimes have surface irregularities caused by the silicone non solidifying properly.

My cleaning cycle is a 15 min IPA bath after print > 1 to 2 hours of UV curing > scrub the part with a soft brush and new IPA.

Anyone knows if this is the best cleaning or if the resin has any chemical that inhibits the silicone from catalysing?

If there is any IPA in the part silicone won’t cure properly. You really need to let the part set for a day before trying to create a mold from it.

I seal mine with spray lacquer and this helps a lot. A good coating of mold release also helps.

I already let the parts dry for a day or more and blow compressed air on them before making the mold for cleaning.

I can’t seal or apply any other layer on top of the part because it would make the part loss detail and my molds are usually for very detailed jewelry.

What type of silicone are you working with? Tin cure or platinum cure?

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Platinum cure

Any impurities on the part can inhibit platinum silicone from cureing ptoperly. Tap water residue can have enough sulfer to inhibit cure.

Tin cure will not have as many issues with contaminants. It can have other issues but it’s worth a try especially for casting wax patterns.

It’s also cheaper.

Will evaluate the tin cure. Do you know the contraction of it? I use the platinum because it has the smaller contraction that I know.

The issue is this only is only happening on formlabs resin, I also make molds from wax and metal parts without issues.

For small parts contraction might not be all that bad.

The Formlabs material takes quite a bit to get cured properly. You must post cure under UV or the sun and do some extra cure from what is normal. If it’s only cured on the surface some of the green resin or IPA that is under the surface can weep out and cause issues.

I do it all the time. DO what you are doing but also coat the parts with a release agent. I use a teaspoon of Vaseline in about 3 ounces of mineral spirits. Just paint a light coat on the parts, sometimes two coats.

Bingo! That’s the problem, platinum is great stuff, but is inhibited by everything, the glues in most tapes, latex, sometimes CA glue. you can try to paint them with a thin coat of a paint that it will cure against - I have always hated working with platinum rubber for that reason, tin is very forgiving!

I always do a quick primer coat on my parts. It really helps

As well as hitting it with lacquer, for platinum silicone, which is extremely sensitive to contaminants, I’d suggest a couple of coats of Inhibit-X: It’s specially formulated to discourage that non-cure response that makes platinum-cure silicone so difficult to work with.

I don’t advise using thick primers, or (especially) petroleum jelly, which will obscure the fine detail you’re going through all this trouble to replicate.

Andrew Werby

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