As shown in the previous post, we needed to step up the game strength-wise for this set of parts. Fortunately, the shape is immanently castable, and with next to no modification of the part itself (only some post-processing) it’s ready to turn into solid aluminum. I printed the parts again in the same orientation, but in natural PLA, which I unfortunately didn’t get pictures of. The parts do have to be scaled by 103% to account for shrinkage in the aluminum after it cools.
Afterwards, the parts were sprued and vented with wax and 3mm PLA, respectively. You can see them here looking like little upside down bugs in the lower-right of the picture:
The fat blocks of wax are used to flow the aluminum in, and the spindly bits of PLA are used to vent air out. I placed the parts in a steel tube, capped with wax. The tubes are shown below, the wax-capped versions are not:
From that, I covered it with jewelers investment, vacuumed the air bubbles out, and allowed it to cure:
The resultant plaster-filled tubes were baked in a searing hot kiln for 10 hours to turn all the plastic into … nothing, and prepare the molds for the equally searing hot molten aluminum to be poured in:
The remainder of the process happened quickly, and was instead captured on a pair of rather uninteresting videos (they were a lot more intense actually being there):
After the parts came out, some cleanup to remove the aluminum sprues, and beadblasting, and they were ready to ship:
And, finally, here they are installed:
The process of being able to cast aluminum parts directly from printed parts meant my customer didn’t have to redesign his part at all, and we could avoid expensive billet CNC work. While the CNC would have produced a prettier part, the extra expense was wholly unnecessary in his case. In addition, the pre-casting blanks were able to be used to verify dimensions, allowing for much quicker turnaround on designs before committing one to metal.