The reason why I started vacuum assisted was this casting:
Casting #22. Protective cover for compressor linkage.
Since I started experimenting with the vacuum assisted casting, that thing never worked. First, because of wrong parameters. But I found them two weeks ago. And second, because for an still unexplainable reason, the inner core was too big. So I took that one, measured, compared it with the CAD. Too big. Verified it against the G-code, too big also.
So today, I milled it again …
As cast, with the gate still in place.
A old reject, with the gate sawn off. The problem of that casting is the thin shell (2 mm) and the fact, that the melt has a long way to reach the end of the cavity.
3 core boxes. The lower one is for the core. A core out of core sand to go into a mould out of core sand.
The cores. The core I'm holding in my hand is the core. The half cones match into the core moulds and align that core within.
One half of the core mould with the core sitting at its place. The slanted face at the lower left, I have to manually sand down. Or the core box would have been gotten more complicated. Sanding down is quick, I just rub the part on the table, the core provides its own sand for sanding.
And today, while having a walk to lunch, I made an invention.
DTC. Short for DeskTopCasting.
You already know, that I do embed core sand molds in oil sand and cast them there. This is for castings that need more feeding like the compressor head. They don't work with vacuum assisted casting (unless I change the mould and make it much bigger).
The idea was to cast a pot for the melt that is glued on the mould and provide enough room for hot metal to feed the casting while cooling.
Well that's such a pot glued to a mould.
Two tests, all worked like I wanted them. One is the head for the compressor, the other one the fuel pump.
Time to have a beer ...
Nick