ME 203, the manufacturing and design class I'm taking, has weekly four-hour lab sections during which you learn one new process. By the end of the quarter each student has a few small projects, including a welded cube, a Stanford seal made of bronze and a simple magnifying glass. The purpose of these projects is to teach you how to mill, turn (on a lathe), weld, sand blast, and many other useful building skills. The first couple of sessions were mainly review, since I spent countless hours in MIT's Pappalardo Lab making robots and oil filter spinners among many other things. This week's lab of sand casting, however, was 100% new to me. Sand casting is so much more exciting to watch than the slow, meticulous machining processes I have used in the past. There is also a lot more heavy lifting involved, and you get a lot dirtier.
The first step is creating the mold itself. There are two resin forms: one for the front half of the seal and one for the back half. You tightly pack layers of powder, new (red) sand, then old (blackened) sand around the forms, then remove them and use a bellows to blow out stray bits of sand.
Next, you wait until the metal is hot enough to pour. In our case, that was 2020 degrees Fahrenheit. In order to measure how hot the metal is, you need a special temperature probe that can withstand the heat - or not, as was the case when one of ours burned off in the crucible.
In order to even get close to the crucible of metal at that point, you need to wear heat reflective clothing. I thought these looked pretty cool.
Once the metal was ready for pouring, our TAs kicked us all out of the room and went down the line, rationing out the molten metal to our line of waiting molds.
Unfortunately, my mold was at the very end of the row. A couple of other molds were too leaky, meaning that they ran out of metal part way through mine. I'm not too sad about this, since I don't have much use for a 5-pound piece of brass, but I was disappointed that I didn't get to see how well my mold held up.