Posted by Dan Shockley on Wednesday, May 29, 2002 at 9:10AM :
In Reply to: Lost Foam Casting used on todays blocks posted by jack cain on Wednesday, May 29, 2002 at 8:54AM :
There are not that many engine blocks made by lost foam. GM has a few(saturn blocks and maybe a few more now) but most are still some type of sand process. The tolerances with lost foam are not as good as you indicate. The foam is very sensitive to atmospheric conditions tends to swell/shrink up to a few percent with very small changes in temp./humidity/pressure. If you are interested in making a one-off casting, I would recommend investment casting. In order to make a foam pattern, you must have a very complex pattern that includes cores and all the other items you talked about. Of course you can glue several pieces together to avoid some of the complexity. Foam mold costs are usually in the tens of thousands for fist-size parts. It is possible to hand carve a pattern, however the foam is not going to be of the quality and type that will produce the best casting. Hand carving would only be appropriate for an ornamental casting.
Have a great day,
Dan