I had been considering buying some low temperature rubber and experimenting with making moulds directly from prints to allow me to produce waxes for casting, however, I decided to just go ahead and do it with my standard rubber and it’s worked out pretty well.
This image shows the model printed in castable resin, the white substance is talc.
The rubber is Castaldo pre-cut yellow, I used 6 layers when I would normally use 7, however, I wanted to cut down on the vulcanising time. I had this in the machine for 45 minutes. I’m going to do a 7 layer mould next time.
I was a bit quick in opening up the mould and the pattern separated at the top, it was still quite fluid though and I managed to reform it round a ring mandrel before dropping it in water to cool it down
I think it’s quite good for a first try, most of the detail seems to have transferred into the wax despite the talc on the pattern. Once I’ve cast some waxes from it I’ll post the results.
I tend to use RTV two-part urethane…I haven’t created a mold yet, but I don’t foresee any problems. I’ll have to remember to spray a separator on the mold. Someday, I’ll invest in a vulcanizing solution!
I tried RTV on some resin from a Projet 1200 it was green in colour - don’t know the name of the resin. It had a slightly sticky surface perhaps it was not fully cured. However it seemed to interfere with the curing of the RTV and the RTV failed to cure where it was in contact with the green resin. The resulting mould was unusable.
One of the resin manufactures told me the resin had been tested to 300’F which is about the same temp. I asked specifically for the same reason…glad to know it works! Has anyone tried the 2 part mold generator? http://www.thingiverse.com/thing:31581 maybe there are others, would be nice to just push a button and have your shape convert to a mold of itself , print out and then shoot the wax. Don’t know how many waxes you could get before it went bad but would be interesting.
I hadn’t seen that on thingiverse but it looks quite interesting, I’ll have to download and try it. Obviously the resin could cope easily with the temp of wax. It might be worth trying in a flexible resin.
I had issues with Castaldo with shrinkage but Romanoff Periwinkle was better but not always in stock. Price is about the same. Alternatively you can use the 2 part putty type that is cold mold, uses no heat and can be formed by hand from Contenti.
@KenCitron I’ve been seeing around half a ring size shrinkage in just the prints. I’m still experimenting with prints and vulcanising and am looking at shrinkage. Thanks for the tips on alternatives, I’m also waiting for the Castaldo low temp rubber to arrive after @ESpy mentioned it previously.
Looks like Romanoff discontinued the periwinkle which is unfortunate since it worked well with resin based prints. However the cold mold compound is still available from Contenti: https://contenti.com/jewelry-casting-supplies/jewelry-mold-rubber/cold-mold-compound
It also has 0 shrink. If you use the Cold Mold you need to mix It really well but over all it is easy to work with and you can still press it in a vulcanizer but just don’t need any heat.
I stopped using those rubbers because they deflect too much in my spin casting machine due to the low durometer. The Cold Mold has a pretty good shelf life, they say 6 months but I still have a little bit that is over a year old and still works.
