Help with armor/shell pieces

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Help with armor/shell pieces

Postby Angel Bun » Wed Oct 10, 2012 6:36 pm

Alrighty, so, I'm a relative newbie to this hobby, I've never done a custom jointed figure before. I have, however, worked on a variety of projects and mediums, including some sculpting and modification. My first custom figures are three Transformers Prime FE Starscreams (Deluxe Class), working towards character accuracy. The other two will become Thundercracker and Skywarp, following my own designs.

Right now, the part I'm most iffy about are the shoulder pieces. While I'm not going to drive myself to the brink of insanity by trying to get it 100% correct, I'd like to get their shoulders looking nice.

The shoulders are basically a stack of thin shells.

What should I use to make these thin shell shoulder pieces?

They need to be thin, but light and strong. Something in plastic would be ideal, but I need to be able to paint and sand it.


Could I try heating up plastic with a heat gun or heated sand/salt, etc, to bend it into shape (with or without a drape mold)? What sort of plastic should I use for this?

Should I try casting the pieces? I know that bubbles can be a problem (pinhole bubbles would be fine, easy enough to fill, but not larger), what sort of casting materials should I use? I'm hoping that there's something simple that doesn't require the use of a vacuum chamber/pressure pot (expensive!)

I've worked with Apoxie Sculpt before, but I think it'll be too heavy for this application and too brittle as well at the thickness I'll be working at.

Remember, I'm working in triplicate! While each outer piece will be slightly different from one another, the main form will be the same.

Any other suggestions are more than welcome!
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Angel Bun
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Re: Help with armor/shell pieces

Postby Angel Bun » Wed May 22, 2013 8:15 pm

Well, I may as well post my results here, since nobody answered. :-s

I first tried heating plastic using a heat gun and also with a candle, both ended in failure since it wouldn't follow the complex angles involved in the shoulder piece. Both a drape and a negative mold. The plastic I used was from blister and clamshell packaging, easy enough to get a hold of. If the curve had only been in one dimension, it seemed like it might have worked. Even with pieces that started out in vaguely the right shape, they straightened out on heating.

After that, I broke down and bought casting supplies (expensive!). Both products from Smooth-On; Task 4, which is a 2-part resin that cures hard and preforms especially well in super thin pieces. And Mold Star 30, a 2-part platinum cure silicone that makes sturdy molds that have a minimum of shrinkage.

Platinum cure silicone is supposed to be rather tricky to work with, but I didn't have any problems. I simply used a non-drying modelling clay that had no sulphur in it (extremely important).

I took my first clean casting and have tooled it fairly extensively, thinning it down, shaping it more intricately, and adding the socket end of a ball-joint into the inside. Once I've gotten everything perfect, I will make a new mold of this piece and cast what I need. The old mold will be cut up and reused as mold filler.

The downsides of Task 4; First and I think foremost, is cure time. It takes forever. 16 Hours in optimum conditions. Aka 23-4˚C 'Room Temperature'. My house is never that warm, except maybe in the summer. So usually it's more like 18-19 hours before you can take your casting out of its mold. ](*,)
Second; Air bubbles. Holy crud. Maybe it's just me, but I'm getting an enormous amount of pinhole bubbles in a lot of my castings. Apoxie sculpt doesn't like going into pinholes without a fight, and there's no way I'd risk using something else that might have sulphur in it.

Mold Star 30; no complaints, other than the price. This stuff works like a dream, I haven't had a single problem with it. Even air bubbles haven't really been a problem.

Hope this helps somebody else out.
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