Casting without a Pressure Pot is difficult, adding the pressure pot and switching to product with a working time long enough to be compatible with Pressure casting has increased my quality production 100 fold.
I'm using Smooth-on Mold Max 15T to make the molds, parts are cast in Smooth-on Task 4 uretane and colored with Smooth-on dyes.
I had both crotch molds in the pot last night, so you're lucky...you get to see both ways I know to cast an ARAH crotch
http://img.photobucket.com/albums/v644/ ... G_8883.jpg
http://img.photobucket.com/albums/v644/ ... G_8884.jpg
The 1st method I call a squish mold....it's a 2 part mold that can be used with or without pressure. it's a simple bowl and a plug...you put resin in the bowl, and squish the plug down in to make your crotch. To make this one I started by filling the crotch with clay...the part represented by the plug is clay and you pour the "bowl" part of the mold 1st. once the rubber cures, flip the mold over, remove the clay plug, add mold release, and then pour the plug half of the rubber...let it cure.
Here I've pulled the plug out...you can see a rim of flash around the top of the waist and around the mold.
Flexing the crotch out of the mold most of the flash breaks away...quick clean up with an exacto and a bit of sand paper is about all you'll need to do.
2nd method is a version of a Split Glove mold...I wouldn't recommend this unless you're filling your molds with a syringe and pressure casting.
Here's the final untrimmed part, mounted on 2 sprues, they act as a fill and vent hole for your part.
I don't know if you can see the "U" shaped cut that goes from edge to edge connecting both sprue holes.
The 1st time you make this mold, after you've cut that "U" shape you'll need to flex the mold quite a bit and cut the bit of rubber between the "Grundle" and the bottom of the mold.
Clean up on the part is pretty easy...the flash peels away with your finger nail or an exacto, the sprues are easy enough to cut and can be dremel'd down so they're not seen.
