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Materials for Casting Custom Parts?
June 27, 2010 8:50 PM   Subscribe

As a hobbyist robot builder/random object fabricator, what options are available to me for making custom parts out of plastic or similar materials?

I build robots and similar mechanical creations as a hobby, and I often come across the need for a custom part, such as a bracket for a servo or a gripper for a robotic arm. I don't want these custom parts to break easily, but I don't expect them to be as strong as metal.

To clarify, I'm not looking for online services where I provide a CAD file and a large sum of money and get a box in the mail with the part I need. I'm looking for stuff I can do at home, and I understand it won't look as good or be as high in quality.

I'm picturing something involving a mold, and pouring some substance into it. Does this kind of thing exist on a hobbyist level? To complicate things, I live in an apartment, so I don't really have a garage I can do this stuff in. So anything I use would have to be safe to do on a plastic dropcloth or something.

If such a substance exists, what would I use to make the mold and where can I find some resources to help me learn how to create a suitable mold?

Finally, I've heard of Polymorph/Shapelock/Friendly Plastic, is that the direction I need to be looking? If so, do any of you have experience with the stuff?

Thanks MeFi! I'm sure some of you guys are more familiar with modelmaking and similar hobbies so I'm sure someone out there can help me out.
posted by DMan to Science & Nature (9 answers total) 10 users marked this as a favorite
Carbon fiber & Silicone mold
posted by hortense at 9:08 PM on June 27, 2010

Is it the sort of thing where you could pick up a 3D printer kit from MakerBot and start using that? I don't know how loud a CupCake CNC is, so I'm not sure if you'd piss off the neighbors. You could probably ask any number of folks in the hackerspace community, though, and they could tell you, or tell you what a better approach would be.
posted by fairytale of los angeles at 10:08 PM on June 27, 2010 [1 favorite]

Cupcake CNC doesn't make much noise.

Shapelock is probably your best bet to start with.

Perhaps you can start with sheets of lexan/plexi and drill them and glue them to get started?
posted by joshu at 10:45 PM on June 27, 2010

In general I wouldn't mess with molding custom parts. It takes a lot of work and is a finicky process just to produce a single item. But yes, silicone molding and polyester resin compounds are available at your local art supply store and they will produce usable components. But it will be frustrating and time consuming to work with. To do it properly you need a vacuum chamber and high quality (expensive) silicone. On the up side you can do it in your apartment. It's not particularly messy or toxic. I've done it in my kitchen quite often.

I agree with the above that a Makerbot is something to seriously consider. In general the stuff it produces will be sturdy enough for what you're looking for. The materials it prints with are cheap and it can safely and easily be run in an apartment. (low noise, low fumes.) But the real advantage is speed. With molding you have to carve an original, make a mold (often a two or three piece mold) and then cast it. If you need to tweak something you have to start all over. With Makerbot you design, then print. If it's not right you tweak and print again. From concept to completed item can be hours rather than days. (Or weeks.)

Shapelock is awesome. And reusable.

A lot of things like brackets, cases, servo horns, etc can be laser cut very easily. See if someone nearby has a laser cutter that you use. (or they can use on your behalf.)

(And I don't think that Shapeways is particularly expensive, especially for plastic. The prices on 3d printing have dropped tremendously.)
posted by Ookseer at 11:01 PM on June 27, 2010

I've use mold material and casting resin from Smooth On and been pretty happy. It definitely isn't super tough (well, there are super tough varieties, but they are much more finicky than the plastic resin.)
posted by ecurtz at 6:02 AM on June 28, 2010

Shapelock is indeed pretty sweet.

Do you have a Tap Plastics nearby? They do all kinds of stuff like this. You carve your part out of wax, make a silicone mold, then cast it in some hard resin. The only drawback is you need good ventilation since the solvents are nasty. The nice thing about Tap is they usually have experts on staff who can help you.
posted by chairface at 12:50 PM on June 28, 2010

And there's the other end of the complexity spectrum, good ol' Sculpey. It shrinks a bit as it sets, so you have to calibrate your process.
posted by phliar at 5:44 PM on June 28, 2010

Sugru, moldable silicone.

Wood's Metal
posted by Confess, Fletch at 6:30 PM on June 28, 2010

Just to follow up on some of the materials that have been posted:

Sculpey is fine material but is far too brittle to be used in anything that is under stress. It's purely decorative. However if you want to go the "make a mold" route, you can use Sculpey to make your original. Give it a coat or two of polyurethane it before you make a mold from it though. It's slightly porous and will be hard to demold otherwise.

Sugru is fantastic, but it does set soft. (That's the point.) It's great for bumpers and grips, etc. It doesn't have great wear characteristics, so don't use it for protection against something that gets rubbed or banged a lot. Also after it sets almost nothing will stick to it, which can be a plus or a minus depending on the application.
posted by Ookseer at 7:33 PM on June 29, 2010

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