Casting Vs. CNC

[Lextreme II]

My brother and I are playing around with a supercharger manifold. Would it be easier to cnc a block of aluminum instead of casting a supercharger manifold?

 

[SCV8]

Maybe, but much more expensive to start with a large billet I'd guess.
There are some neat casting process' that involve making a part from the hard foam that you buy at home depot to insulate with, it's polypropylene,I believe, is usually blue, or pink, and it can be used to make casting forms out of. It sands very well, but is irritating to work with; eye protection required.

Once you have a correct form carved, or machined, allowing for the shrinkage of aluminum(1/4" per foot I believe), you have the foundry pack sand around the form, in a box with a hole on top to add the molten aluminum.

I have a foundry near my house, and have thought about how easy it could be to creat a new base for some ITBs, or a slightly different process for some camshaft blanks.

A co-worker has been doing basic sand casting of tether car models for years, an obscure, collector hobby shared by a handful of mostly older enthusiasts. The models are flawless when completed, and sell for several thousand dollars, by word of mouth, interesting I thought.

 

[vvillium3]

definalty cnc

well, imho I believe that just breaking down and buying a good chunk of say 6061 or even a 7000 series aluminum(strength) and find a machine shop to make one for you. Might be a little move exspensive, but definatly a lot of less headache.
I am a journyman mold machinist here in michigan(work on plastic injection molds, and lots of cnc experience(just got a 5 axis machine in our shop)), and I would even want to sit and try to hand bench in a part from foam (by the way polypropelyne is a plastic) and try to get it perfect. Especially with shrinkage from the casting and all the other factors. Where the other route is you pay someone to cut it for you and have it right the first time. maybe even saving a little money. Because if you mess up your fault, they mess up they pick up the tab for try #2.
And a little extra idea for you could be to make it out of smaller plates and have them then welded together after the were machined to the right size.....

 

[Taurine]

Depending on the quality of the casting you might run into problems with small bubbles being left in the molten material as it sets. Not really an ideal factor in a component which would be containing pressure (ie s/c manifold).