And here it is!
Before we can make the mold, we need to create the mold positive. This is basically a case half, except we make it out of plastic. It’s not just any case half though – it’s a reproduction of our raw casting, which means that it is dimensionally different than an actual case, and it lacks some of the holes and features that a finished case would have, because those will be machined on the case post-mold.
Although scanning the case was a monumental and expensive effort, in and of itself, a Solidworks drawing of a case is pretty much useless for building the tooling needed to actually build a case.
But it’s a start.
This is where the toolmaker comes in. In order to cast new cases, you need to build tooling. Mainly, this is where the bulk of the expense lies in this little project.
Also, and super importantly, the case doesn’t pop out of the mold looking like one that’s in your car. Here are the differences:
In short, the Solidworks drawing needs to be worked over by a team of tooling and pattern makers into something that can be used to make a mold. Which is very, very expensive!
When we decided to reproduce a Porsche® air cooled flat 6 engine case, the dilemma was which one exactly we should invest in making. It was a hard decision; there are many great cases. We were initially partial to an aluminum version of a 7R mag case, but that has its limitations. Some suggested an RSR case, with its associated head stud spacing.
In the end, we went with a 3.6 964® style case, for several reasons.
We had a 3.6 case on hand, so we decided to use it as a basis for reproduction. Cases, however, are fairly complicated parts to reproduce; it was critical that the case be able to accept standard internals, and thus the dimensions of the case were critical.
The only real way to capture the case dimensions was to have each case half scanned, and so that’s what we did. We scanned each half to 50 microns, and then created a mesh model from that scan data which was then extrapolate into an IGES / STEP file by an engineer. From there, it was converted into a Solidworks .sldprt file, with a full feature tree.
A full feature tree allows us to use Solidworks to change any part of the case design on the fly, while having the software adjust the remaining parameters. Want bigger spigots? No problem, it’s a mouse click away.