First a disclaimer: I'm really new to this, but very excited about giving it a shot. I'm also very limited on fundage, and whatever I spend on backyard industrial supplies is coming directly out of my beer making funds...
I'm currently machining a wax part about the size and shape of a distributer cap for your car (Actually going to replace the distributer cap, as it is a housing for a DIY distributerless ignition system), with a wall thickness of .1875" I would like to cast it in aluminum using some sort of investment method (I suppose) (since dummy here didn't bother to design in any draft on the part!), partially for the education of it, since there are probably some urethanes or epoxys out there that would take the heat and abuse this part needs to be able to take, but aluminum would have more bling factor.
First off, I've got a little benchtop CNC, and the detail and complexity of this part is taking FOREVER to complete even in wax. From what I've read hardly anyone casts something exactly right the first time, so I need to be able to make some copies (besides just machining another one) of my wax master. Silicone mold maybe? There are no undercuts on this part, but there is also no draft at all, and its about 2" deep. Any advice or suggestions for making accurate wax copies?
Next, onto the real mold-
Where should I get investment ceramic materials, and what specifically should I be using for an application like this? And then after the wax is coated with investment, should I bury this whole thing in sand too? Is backyard sand OK here (I live on the coast, the backyard is mostly sand anyway), or will I want to find something special?
With these thin walls I was thinking that I would need to somehow forcibly move the molten aluminum to completely fill the cavity with minimum voids... which then got me to thinking about building my own junkyard centripetal casting machine from a busted air compresser motor, a wheel rim, and a 50-gallon drum (to shield me from the flying molten metal)
So then I start to thinking, how fast should this thing spin? I assume I would want to minimze the sprue length (bringing the casting closer to the center of the rim) but maximize the G's (crank up the RPM, maybe with a pully) but keep the whole contraption balanced enough to not fall appart! Short question: how many G's should my casting see?