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Hey everyone,
I'm looking for advice on what material would be ideal for my molding application. I work in a research lab which is developing small drone like robots and we are hoping to develop a casing to contain the drone's hardware. As a result the mold needs to be very lightweight and have thin but rigid walls to protect the mechanism.
So far I have looked into carbon fiber and foam molding options but was wondering if anyone had other suggestions for materials.
Thanks!
Mothman,
A lot depends on the complexity of the geometry, the number of casings you want to create, and of course cost.
Depending on the shape, size and aesthetics you may even consider vacuum formed plastic sheet. We'd be happy to work with you on this process.
I'm not clear on why the mold has to be light in weight. You can make a light casting from a heavy mold. If vacuum-forming won't work, I'd say a urethane foam into a silicone rubber mold might be easiest. But if you need a lot of structural strength, then a fiber-resin layup into a rigid mold would probably be your best bet.
Thanks for the replies all,
Being new to moldmaking I may have used some of the wrong terminology in my initial post, the mold itself doesn't have to be lightweight but the resulting casting should be. The casting doesn't have to be super precise but it should be smooth enough for wind tunnel testing.
the casing itself is going to be between 3 and 4 inches long and less than 2 inches wide and tall. and has several protruding features which we would like to preserve if possible. Honestly we only really need 2-3 casings from each mold since we were hoping to make variations of the casing for a variety of functions.
To preserve some of the features we had already intended to vacuum form the carbon fiber to the mold. If the mold is made of spray foam can it still be vacuum formed or will it collapse under the pressure.
Thanks again!
You might be able to use a 3d printer if it's that small. Print the female, including the holes for drawing down the vacuum. Sand it to remove the strata lines and cover with release wax, lay in a gel coat then the fibre and epoxy. Or do the same using a mill/router and softwood, just seal it properly after sanding and before drilling the vac holes.
If you are going to cast the part (I.e. Your drone casing), you can make a simple silicone mold with a hard shell made from epoxy putty. Google "hard shell silicone molds" and you'll find plenty of tutorials.
To cast something both strong, light and thin, you will need to reinforce the resin. If you don't have time and patience for a learning curve, I would suggest casting with epoxy reinforced with chopped carbon fiber (sold by the pound on eBay). If money is no object, add carbon nanotubes ($250 per kg).
If you are looking for the max strength and the least weight possible, you will want to use a woven carbon fiber or fiberglass and this will require a rigid mold. There are plenty of YouTube videos on this but it's much harder than casting in silicone. There will be a learning curve. I use fiberglass and / or carbon fiber to make my rigid molds to make cf parts.
Either way, you will want to start with a plug which is the master used to make the mold from. I like to carve mine from urethane foam and coat them with a black epoxy gel coat from ACP composites. If you already have a prototype to copy, that is your plug.
Learned a lot watching videos from these guys
https://www.youtube.com/user/SmoothOnInc
https://www.youtube.com/user/brickintheyard
https://www.youtube.com/user/freemanmfg
https://www.youtube.com/user/BJBEnterprises
[edit] Of particular interest:
https://www.youtube.com/watch?v=ZdNIpJ2IWeE
If you sign up for their newsletter, you'll have full access to their videos
https://www.youtube.com/watch?v=iRj6xzNx7P4
https://www.youtube.com/watch?v=tnY86LIHf_I