Need help selecting a resin

After a lot of Googling and research, I've found myself stumped when looking for a resin to use with a set of silicone molds I'm planning.



I'm presently working on modeling the Infinity Pistol from Borderlands 2. I am planning a run of nine guns, each having LED lighting to give them the elemental effect. In order to keep plastic use down, the guns will be roto/slush cast, also allowing me to easily suspend and backlight the glowing regions. In addition, Ideally, I would like to be able to rotocast the pieces in a translucent resin died to the correct color (neon green, blue, or orange), paint all areas that don't glow, but leave glowing areas untouched.

For any particular attribute, I know what to look for (Smooth-Cast 300/320 for basic casting, Smooth-Cast 65D for roto, etc). But for all three, I struggle.

Here are my must haves:

• Must be roto or slush cast-able
• Must be semi-translucent, enough so that a backlight can illuminate it
• Must be able to be dyed colors
• Must be able to take paint

Does anyone here have any recommendations? I've seen people like Bill Doran use Smooth-Cast 65D, but have heard stories that it doesn't take paint well. If it's just an issue with it needing primer, that's no big deal, but I absolutely need to be able to paint them.

Thanks!

I'm no expert but I've heard others speak of additives to promote a good "spin" (vice "pour"...) so resins not normally rotocast still perform okay.

What about looking at clear resins then just tinting to get the color you want. Or is that what you meant?
Just throwing in a thought to help get things moving...

R/ Robert

Slukaj said:

After a lot of Googling and research, I've found myself stumped when looking for a resin to use with a set of silicone molds I'm planning.

View attachment 655374

I'm presently working on modeling the Infinity Pistol from Borderlands 2. I am planning a run of nine guns, each having LED lighting to give them the elemental effect. In order to keep plastic use down, the guns will be roto/slush cast, also allowing me to easily suspend and backlight the glowing regions. In addition, Ideally, I would like to be able to rotocast the pieces in a translucent resin died to the correct color (neon green, blue, or orange), paint all areas that don't glow, but leave glowing areas untouched.

For any particular attribute, I know what to look for (Smooth-Cast 300/320 for basic casting, Smooth-Cast 65D for roto, etc). But for all three, I struggle.

Here are my must haves:

• Must be roto or slush cast-able
• Must be semi-translucent, enough so that a backlight can illuminate it
• Must be able to be dyed colors
• Must be able to take paint

Does anyone here have any recommendations? I've seen people like Bill Doran use Smooth-Cast 65D, but have heard stories that it doesn't take paint well. If it's just an issue with it needing primer, that's no big deal, but I absolutely need to be able to paint them.

Thanks!

Click to expand...

There is great set of videos by punished props on casting and moulding and which resins to use , mostly smooth on but it's still relevant to other resins
bill covers rotocasting , simple and complex moods ,
start with this
https://youtu.be/Wp3CVObpl2s

rbeach84 said:

I'm no expert but I've heard others speak of additives to promote a good "spin" (vice "pour"...) so resins not normally rotocast still perform okay.

What about looking at clear resins then just tinting to get the color you want. Or is that what you meant?
Just throwing in a thought to help get things moving...

R/ Robert

Click to expand...

I'd be fine with a transparent resin but my understanding is that they don't roto/slush cast well, namely because of the bubbles that form unless pressure casting is used. If I had a pressure chamber large enough to hold a small rotocast machine, I'd certainly consider it, but unfortunately that's waaaaay outside of my price range.

Vacformedhero said:

There is great set of videos by punished props on casting and moulding and which resins to use , mostly smooth on but it's still relevant to other resins
bill covers rotocasting , simple and complex moods ,
start with this
https://youtu.be/Wp3CVObpl2s

Click to expand...

Doran is where I got the idea to use Smooth-Cast 325 from (it's what he cast his Nuka Cola bottles out of). Until I read about how it allegedly doesn't like paint, I was planning on just following his videos on the matter.

Problem is that paint is a necessity for me, and I can't pre-paint the molds.

I was thinking two factors relate to using a clear resin. One, you'd want to degas under vacuum before the pour, since bubbles might be an issue anyway, and two, if you give it a pretty good spin vertically initially, wouldn't the bubbles migrate to the interior area? Since there is no inner wall, they should just pop out... I know the idea of rotocast is to slowly spin the mold along a horizontal axis which (hopefully) prevents air entrainment, though I'd image if things were not just 'so', then you'd perhaps see a waterfalling effect as resin drips from top to bottom during the rotation. A high speed spin would need a robust rig to resist the forces, though less so when vertical as the force would be more balanced (i.e., no gravity imbalance.) However it would offer the advantage of a uniform wall thickness in the casting.

Hmm, does rotocast involve a two-axis spin by chance? I can see a rig configured so it spins fast and starts in a vertical position then you slowly crank it over on its side to finish, still at a fast spin (or a gradually slower spin as the resin sets...)

Gotta check out Bill's video.

R/ Robert

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Just did it, Bill's a hoot. Noticed a comment about smaller parts taking longer to 'set' because less heat is generated, slowing the reaction. Sounds like a case for having a warming box...

I think it could be possible that spinning would put enough pressure on the plastic to degas it, but I know a lot of these plastics require 60psi to properly pressurize, so I shudder to imagine how fast it'd need to spin.

You de-gas silicon, you compress resin.

When mixing up silicon you place it in a vacuum chamber to pull all (most) of the bubbles out before pour.

When casting in plastic you place the entire thing in a pressure pot and compress it, this doesnt attempt to pull the gas from the resin but forces the bubbles deep inside and makes them tiny, too small to really see/feel.

Talk to Mike Knott at MPK http://moldmakingsilicone.com/

You can de-gas resin before you pour it into your mold. If the resin has a long enough cure time, it helps to get out the bubbles that the mixing process creates.
Pressurizing after you pour resin into your molds helps squash any bubbles so they are smaller.

Right, de-gassing can be used on resin (before the pour) also but sometimes too short a working time isn't practical, though since it can take a bit of time to draw the vacuum 'down'.

R/ Robert

I tried experimenting with a few semi-translucent resins in my rotocaster and the casts came out loaded with bubbles. When pressure casting with these resins, parts come out beautifully, as expected, with not a single flaw or bubble.

I have a vacuum degassing setup but it can't be used with typical 3 minute gel time resin...there simply isn't enough time to degas the resin, pour it into the mold and still have the resin fluid enough to coat the mold properly in the rotocaster. I'd first be looking for a semi-translucent resin with a working time of at least 15 minutes so there'd be time to degas....I think that'll give you a good chance of reducing (if not eliminating) bubbles. Maybe see if Specialty Resin can mix up something for you?

DonS said:

I tried experimenting with a few semi-translucent resins in my rotocaster and the casts came out loaded with bubbles. When pressure casting with these resins, parts come out beautifully, as expected, with not a single flaw or bubble.

I have a vacuum degassing setup but it can't be used with typical 3 minute gel time resin...there simply isn't enough time to degas the resin, pour it into the mold and still have the resin fluid enough to coat the mold properly in the rotocaster. I'd first be looking for a semi-translucent resin with a working time of at least 15 minutes so there'd be time to degas....I think that'll give you a good chance of reducing (if not eliminating) bubbles. Maybe see if Specialty Resin can mix up something for you?

Click to expand...

Looks like Smooth-On also makes slower-curing version of 325, namely 326 and 327 which has a pot life of 9 minutes and 20 minutes respectively (as opposed to 325's 2.5 minutes), and a cure time of 60 minutes and 4 hours (as opposed to 10 minutes).

But I wonder if the bubbles would return with that high of a cure time...

Air might be reintroduced to a degassed batch of resin as it's spun in a rotocaster...but the only way to know for sure is experiment.

I'm not certain time would be a factor...after I degas a batch of silicone and pour it, a few bubbles rise to the top and burst, but nothing like what's seen in an un-degassed batch...and the cure time for the silicone is 24 hours.