kyussinchains wrote:
sorry to hijack someone else's thread, but how do you go about making two part moulds? I assume you pour the silicone into a former, then add the component and some pegs to align the other half, allow to dry, coat in a release agent and then add a second layer of silicone to create the other half. is this correct?
Not how it is generally done, though might work.
The traditional way is to get some plasticine (that doesnt react/inhibit your RTV [check your RTV data sheet]) and roll it out into a sheet. Then pick out an indentation for your master so that it sits with ~half exposed, place the master in and push the plasticine in around it to seal. Also stick some key objects (ball bearings) in the plasticine around the edges to allow the 2 mould halves to allign correctly. Build your mould form walls. Pour RTV. Wait your set time. Remove walls. Remove plasticine, leaving master in the RTV mould half you have just poured. Rebuild you mould form walls, give the RTV a coat of RTV-RTV release agent (vaseline disolved in white spirit if you are cheap) let the release carrier evaporate (the white spirit). Pour RTV. Wait set time. Demould.
Remember that for a 2 part mould you will need somewhere for the resin to enter and air to exit, so factor these sprues/runners/risers into your master.