Resin casting question

abledog · Post by **abledog** » Wed Oct 05, 2011 7:43 pm

Okay... I'm learning to cast resin very soon, and I have a scratchbuild project I want to apply this to. My intention is to design this thing so that it can be assembled with a hollow hull. I don't have access to a roto-caster, so I'm figuring out how to build my parts accordingly.

So how thin can my parts be, so that when I cast them I can avoid warping?

Thanks!

Able D

Stu Pidasso · Post by **Stu Pidasso** » Wed Oct 05, 2011 7:47 pm

If you want an accurate response, you might have to post pictures so us in the field can give good advice.

abledog · Post by **abledog** » Wed Oct 05, 2011 7:53 pm

Thanks... I'll have to do that once I'm far enough in the assembly.

Able D

Joseph Osborn · Post by **Joseph Osborn** » Wed Oct 05, 2011 8:39 pm

Just to throw out some ideas: You don't necessarily need a rotocasting machine to do a rotocast piece; you can turn it by hand and get nearly as good results. A rotocasting machine is great for mass production, but it doesn't sound like you intend to make a bunch of parts in a short time. Another alternative may be epoxy fiberglass lay-up in a silicone mold. You can get a very strong and thin shell with very fine surface detail using this method.

Ziz · Post by **Ziz** » Wed Oct 05, 2011 8:54 pm

Rotocasting is only necessary if you're trying to make a large part with no seams on it aside from where the mold splits. If it's going to have edges and mating points where two or more pieces come together to form the whole, you don't have to rotocast it, just do each piece as a normal mold.

abledog · Post by **abledog** » Fri Oct 07, 2011 11:06 pm

Hi guys... here are a couple of illustrations to show what I'm talking about

I'm using sheet styrene..

http://i17.photobucket.com/albums/b95/a ... tic-01.jpg

..but I'm thinking I'll laminate it to make it thicker so I can cast it and avoid a warping problem..

http://i17.photobucket.com/albums/b95/a ... tic-02.jpg

Am I even on the right track here?

Thanks!

Able D

Tankmodeler · Post by **Tankmodeler** » Sun Oct 09, 2011 8:32 pm

You're on the right track, but you also have to take absolute size into account. You'll probably need to add some interior gussets to help it stay the right shape. If the sides are 1/2" x 1", then .060" walls are proabbly OK. If the part is 2" x 4" then the walls should be something like 1/8 or more both to get a good pour and to keep things flat & square. How long you leave the parts in th emould also has an impact on warping. Take them out too soon and they will be soft and prone to moving. Let them set hard and they are less likely to warp, but it will slow down your production rate a lot.

One of the key things about this is that it's a craft not a science. It takes a lot of experience to have a good idea of exactly what will work and even then, there's no guarantees. Even the pros pour crap parts from time to time.

Paul

abledog · Post by **abledog** » Mon Oct 10, 2011 8:23 pm

Thanks Tankmodeler... I came across some basic construction issues that I'll have to address, that in themselves seem to steer me in that direction, (or something close).

This is going to be a big learning curve for me, but I'm excited to learn!

Able D

skymods · Post by **skymods** » Sun Oct 16, 2011 9:35 pm

Abledog, more questions. Why are you making it hollow? For lighting or weight issues?

How large? The size of the part could also make a difference in a casting strategy.

Dave