Quote:
Originally Posted by Don
David, not having the technical background/knowledge, from both a cost and design point of view, basically, how does machining and casting compare to arrive at the desired end product, as a continuation of KMU Aluminum 201 ?
.......sure is impressive.
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Castings are very difficult to get right. There is a ton of engineering and experience that goes into making a casting. You simply don't pour metal down a hole and hope for the best. Sprues, runners, risers, gates, temperature, fluidity, chilling, out gassing, on and on. There are many, many variables in casting. Any small problem in any of them can make a BIG problem in the casting. It is not uncommon to throw away 2, 3, or more castings for every good one you get in a complicated casting when you are starting out. One of the big problems is many times you never know if a casting is good until it is fully machined and you find a big surprise (like a hole) on the final cut.
Machining from billet eliminates most of these problems. It does present its own set of problems, like stress relieving (which is a problem castings have as well--you just can't seem to get away from it) but largely the problems are eliminated.
The strength of a casting vs. a billet (referring to typical alloys here) does not compare--especially at temperature (temperature referring to the temperatures we usually run into with automobiles). Castings soften very quickly in the 250 degree range, which is not uncommon for engines, heads, and calipers. As the temperature goes up, the stiffness (and strength) goes way, way down.
David
