I was wondering what type of shrinkage you get with lost wax/pla, and how much it differs between the shrinkage with sand casting. Ive heard that investment casting gives much better tollerances over part, but not sure how much that is true tho. Im looking for casting something in brass probably, or at minimum, casting it in zamac, but Im just curious how it depends on all different metals to get an idea on what to expect.
Here is the thing, you get wax shrinkage for one, then if you made a silicone mold yep there's shrinkage there, and then the alloy shrinkage... totaling up in the 4 to 5% range with vulcanized molds and about 2% with poured silicone molds when casting 360 brass. Less shrinkage? No just more repeatable results. The shrinkage of the metal is dependent on the composition of the alloy. If the mold does not allow for a part to contract along its length it will find another place to contract giving the illusion that there was less shrinkage. With lost pla you are really only dealing with the shrinkage of the metal and I typically scale them 1% and with parts that measure about 4" x 7" can get a tolerance between .001" and .005" on a good day and .010" on a not so good day... shrink happens...
Presumably, not having to rap on patterns to get them out of the mold as is done in sand casting must also mean slightly less variability from one pour to the next when using lostPLA/wax, or at least it would mean fewer sources of variability, since we're talking about thousandths here... Nice new red banner ya got under your name there Dave... Jeff
