Rubber Mold Thickness

[TonyG]

Could somebody please advise how thick a rubber mold should be over the individual parts you are trying to copy.

I assume not too thick so that you can slightly flex it to pop the part out but what is the minimum thickness you would pour over the parts.

I have to make multiple parts for my 1/72 IJN 25mm guns in sgl, dbl and triple as I need more than one of each on my current build and future builds so I have been slowly making up the parts needed to assemble each as a kit style assembly. Bl##dy slow job when the parts are so small

Many Thanks in advance
Tony

PS Anyone know where to source IJN 25mm barrels in 1/72 from brass?

[biggles2]

I've dabbled a bit in mold making, and casting, and found that the bigger the mold, the thicker it should be. If you're making small molds 1/4" - 1/2" all around the master piece should be enough.

[TonyG]

Thanks Biggles. I figured that it needs just enough to be able to maintain its shape so your measurements make sense.
Cheers
Tony

[PICKETBOAT]

Tony

If you have to make a lot of small components you might be able to reduce the space between each component down to 1/4 inch, with a thicker wall around the outside of the mould. This depends on the shape of the components. Incisions might be necessary to get the original and the finished items out of the mould. Silicon rubber is expensive and there is no point in wasting it by over engineering moulds, however if you skimp on the mould thickness too much it might deform in use. Are you using a pressure chamber to cast? De gassing the rubber will improve quality immensely.
Attached picture shows fittings for one vessel (scale 1/48th) all on two casting bases.

[TonyG]

Tony

If you have to make a lot of small components you might be able to reduce the space between each component down to 1/4 inch, with a thicker wall around the outside of the mould. This depends on the shape of the components. Incisions might be necessary to get the original and the finished items out of the mould. Silicon rubber is expensive and there is no point in wasting it by over engineering moulds, however if you skimp on the mould thickness too much it might deform in use. Are you using a pressure chamber to cast? De gassing the rubber will improve quality immensely.
Attached picture shows fittings for one vessel (scale 1/48th) all on two casting bases.

Wow amazing what can be achieved in such a small space ! Thanks for the info.

Regards
Tony