Mold Making?

[Shinobiwan]

Hi guys,

I'm having some difficulty figuring out the best way to mold a two sided part. I should add that I'm completely new to this!

What I plan to do is machine a master on the CNC out of 100mm Polyurethane board and then make a mold box, placing the master in this, and filling with Silicone rubber. I should add that this is a large part measuring 950x180x100mm. I'm not sure what shore rating silicone to use for this. I'm guessing the 15 Shore A is far too soft for such dimensions? I'll be needing around 20kg for the mold so want to get it right since it'll be an expensive mistake if not.


The main problem though is figuring out how to get the rear side detail into the casting without trapping lots of air or distorting the flat rear side portion of the cast part. The way I've tackled it at the moment is to level fill the mold with the casting resin and that will form a guide for the rear and be perfectly flat. I guess I could leave out the rear details but that'll mean throwing this on the CNC to do that and wasting resin.


I've attached the front and rear views of the part along with the first half of the mold but I would be grateful for suggestions on how to tackle the second half of the mold.

Rear of Master:

Front of Master:

First half of the mold: