Moulding/Casting small detailed pieces

[Jamie Davison]

I have never actually moulded/cast anything before but have read enough tutorials to feel confident that I would be able to do so. The problem is all of these tutorials deal with small to large objects. I need to cast something thats is very, very small. It is about 1cm wide, 1cm long, and about 0.5cm thick. It is not overly detailed but it is not a simple piece. What I need to know is do I go about the same moulding/casting process as I would with a larger object? If so are there specific resins/silicone etc that are best used for small detailed objects? If the process is different, could someone please give me some help as to how to do it. Thanks.

 

[LeMarchand]

can you post a picture of the piece you wish to mold?

 

[Tiki]

I dunno how much you learned from other sources, but for small/very detailed items you may need to look into a vacuum chamber and pump to de-air your silicone when molding. For casting the resin you can either use a vacuum as well, or possibly a pressure pot.

best of luck!

Tiki

 

[Jamie Davison]

I will try to take a decent picture in the morning, but I do not have a great camera so it may not be the best of pictures.

 

[Jamie Davison]

I managed to take a couple of good pictures. As I have already said this thing is 1cm wide/long and about 0.5cm thick. The tubes at the top are very thin guitar string, this can be removed if it will create a problem with casting. However, if possible I would like to keep them, or change them so that they can be cast.

Tiki: I have not read about vacuum chambers. Is this a hard/expensive process?

http://i141.photobucket.com/albums/r58/horuswaspretty/grav2.jpg
http://i141.photobucket.com/albums/r58/horuswaspretty/grav1.jpg

 

[PTK]

i think you'll be alright with some good 2 part casting resin
a pressure pot would help, but they are pricey

something that might help would be to mix your resin, pour it in your mold and take a small/thin rounded off object, like the back of a small cheap paintbrush, and gently go over the detail in the mold with the stick (just don't' use anything sharp that could damage the mold) this will help any tiny air bubbles that might be in the resin against the surface detail float up to the top so you get a better cast

and mold releases can help extend silicone mold life, especially when you have to run the mold a bunch of times.......but in this case i wouldn't use any release (assuming the mold IS silicone) because the detail is so small.

also avoid using things like polyester casting resin, or urethane casting resins that have fillers.

good luck!

 

[Sidewinder]

First, always measure your constituents by weight using a scale with digital readout.
If you take care and 'prod' the mold as mentioned above you should be ok.
I also dust my heavily detailed molds with (200mesh) aluminium powder, this helps draw in the resin to small details like rivets - fill mold with powder, shake a bit then tap out the excess, you'll find a thin layer of powder sticks to the mold - then pour resin. Be careful using fine parted metals though as they can get everywhere, cause respiratory probs, react violently to water etc.
SAS

 

[KingNothing]

To elaborate on Sidewinders idea, I've been using baby power (or talcum powder), to have the same effect. Pour in, rub around and get the excess out with a blowdryer or some other air source. Even the computer duster gas sources work, but they can freeze if you need a lot of air. Also bake the powder in a small oven for a couple hours to dry out any moisture. I've been doing small extractor rods for a revolver, and the knurling comes out great, whereas before it was full of airholes.

 

[Jamie Davison]

Thanks for all the tips, I will give it a go and see how it turns out.

 

[blufive]

If you don't have access to a vacuum chamber, you can buy your rubber from micromark.com . The quality isn't as high as RTV that requires vacuum but it'll work well for a few small parts.