mould and casting help

[TK7903]

Hi everyone.

I'm wanting to make strong (but not brittle) resin parts from a piece Ive made.

Ive been told that RTV silcone is best to make my mould?? :confused

But........ There are soooo many to choose from, and the same problem for the resin.

Im in the UK just incase that matters for products.

Heres a pic of what I want to make in resin.

Any help would gratefully received. :cheers

 

[Honus]

If you get the current issue of Make Magazine ( Vol. 8) Adam Savage has a fantastic resin casting tutorial. You can even buy it as a digital edition.

http://www.makezine.com/magazine/

 

[TK7903]

<div class='quotetop'>QUOTE(Honus @ Nov 30 2006, 02:10 PM) [snapback]1368598[/snapback]</div>

If you get the current issue of Make Magazine ( Vol. 8) Adam Savage has a fantastic resin casting tutorial. You can even buy it as a digital edition.

http://www.makezine.com/magazine/
[/b]

thanks honus,

Would maybe like some "free" advice as money is a bit tight. :lol

 

[cobywan]

Then you have a problem as all RTV materials are EXPENSIVE. A gallon of it is aroun $100US. Resin is about 1/4 that. But in the UK you're choices seem limited if the resin kits I've seen from there are any indication.

 

[REL]

Here's a page on mold making that helped me out when I was learning it.

http://www.danperezstudios.com/workshoppag...ing_casting.htm

And another one here.

http://www.conceptart.org/forums/showthread.php?t=47324

I'm asuming that's a wrist band of some type so you wouldn't need a lot of silicone to cast it, you might try buying a pint instead of a gallon. I think Smooth-on's Moldmax 30 is the best. And if your'e not going to pressure cast it I recommend Smoothcast 305 or 310 slow setting resin.

 

[clonesix]

That piece doesn't look like it would require much silicone or resin. So you will get by for less than $100 (50 BP)

I will say that the silicone will pick up the detail of the wood grain and any surface scratches on the ABS part. If you wish to have a smooth, clean part, I would suggest giving the model a good shot of primer and a good sanding.

How many of these do you wish to make?

I don't know where to find the materials in the UK, but I am sure there are local sources and some of the UK members will chime in. You may need to start another thread requesting UK members advice on sources.

I recommend a tin-base silicone with a 25 -30 shore for this. One kilo should be more than enough.

 

[TK7903]

Thanks guys

Yes it's wrist type size.

I've been speaking to a guy here in the UK, he agrees that the types of RTV and resin is limited.

Also been told to prime it before hand.

So basically, this is the info I have so far.

1. Prime and sand part
2. Place part in small tub (with flat base)
3. Lightly coat part with liquid vaseline (ease of removal)
4. Pour RTV into tub.
5. Discard tub when cured, and remove part from silicone.
6. Mix and pour resin into RTV mould.

Thanks for your help so far guys, is there more I should be thinking about?

 

[Blad]

You'll waste a lot of silicone if you use a tub. You only need 1.5-2cm thickness of silicone to be self-supporting.

You need a simple open mould.

1: Prime & sand.
2: Stick part on a piece of flat board, a piece of MDF, anything as long as it's flat & you need to stick rather than just place as it'll float otherwise.
3: For a small part like that I usually make a case to go around the part about 2cm bigger. If you use a tub you'll waste loads of expensive silicone. The case can be thick card, thin styrene sheet, pretty much anything as long as you can glue it firmly to the base. The shape you need is a 'horseshoe' really.
4: Spray with wax release, liquid vaseline is fine, but spray wax is finer.
5: Mix RTV with activator in a plastic jug or similar, trying to avoid bubbles.
6: Pour slowly into the mould, again trying to avoid bubbles.
7: Follow instructions about demould time, usually 12-24 hours.
8: If you can wait try to leave the mould for a few days before using as this will add to it's longevity.
9: mix & pour 2-part polyurethane fast-cast resin which sets in about 2 minutes and can be de-moulded after 10-15 mins, don't bother with polyester resin which is much cheaper, but a PITA to work with and takes 30-60 minutes to set.

If you make a horseshoe shaped mould rather than a circular one, you'll find you can twist it a little to help release the part. Plus you'll have enough silicone to make another mould when the first one wears out.

I but resin from www.cfsnet.co.uk , but small amounts can be bought on eBay, this guy is pretty good: http://stores.ebay.co.uk/Mould-Making-and-Casting-Supplies

 

[TK7903]

Blad,

Thankyou very much.... :thumbsup

all the info so far is just what I'm after.