Molding and Casting

Joel Gustafson

Great Expectations

I think this was my last time using Fusion. I chose it at first because it seemed friendlier, but this week I got to watch a Rhino power-user up close for the first time and the experience converted me. This is one of those "I did the project at the last minute and am half ashamed of myself and half proud it exists at all" stories.

My final project is (allegedly) a chess set, so I eventually have to make (lots of) chess pieces. I had planned on 3D printing them, but thought I'd try casting one too.

Cue the Problems

This turned out to be very difficult to mill. After wrangling with MasterCAM for a few hours (huge thanks to Paloma for her incredible patience), we discovered that the resulting toolpath had several unavoidable collisions. This was because my design had 1 inch deep walls, and the 1/8 end mill for the Intelitek is shorter than that - but even after lifting the body higher, chopping off the base, and widening the margins on the side.

"It sounds like you need to manage your time better."
Yes. Yes I do. I absolutely do.
Eventually Paloma and Jen had to leave (and it was Tuesday night) and I knew I didn't have a chance at successfully navigating the MasterCAM -> Intelitek journey on my own, I gave up and printed a positive on the 3D printer in the architecture shop. The job took four hours, so I took a nap and came back at midnight.

I then MacGyver'd a bounding container with scrap acrylic and hot glue.

I mixed the Oomoo and poured it into the mold, but realized too late that I had made too little - the tip of the Pawn's base protruded from the Oomoo on both halves. I didn't think I could mix more in time, so I just tilted the entire box (since I don't need as much depth at the top, since the piece gets narrower) and let it set at an angle. This seemed to work, so I went back home and slept for another few hours.

When I came back to check the mold, it turned out that the thick end hand't quite dried, and the edge of the piece's base collapsed a little bit while separating from the 3D print. You can see a bit of wet Oomoo still stuck to the 3D printed positive in the picture above.

When I first mixed Drystone, I added the water to the powder (despite explicit instructions not to do so on the box), and was left with a dry, clumped mess. On the second try, I added the powder to the water and wow it really made a difference - smooth, almost liquid, and very pourable.

After more hour nap, I'd casted a chess piece! Certainly defective and certainly a disappointment, but I'm happy to have gotten a physical object out of this nonetheless.