2018.07.10

My last mold making experiment was a good experiment, and if I learned one thing, it’s that the mold should be flexible to allow for the removal of the piece you are casting without destroying the mold or the casting. (Duh!) Instead of ABS I decided to print a mold using flexible filament. Now, to print flexible filament I had to do a small modification to my extruder lever to allow the insertion of a piece of PTFE tubing so that the filament wouldn’t bend over before it fed into the feed gear. Once I did that, I was printing flexible filament (very slowly.)

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I decided to start with something less complex, and used a 2.5D object instead of a 3D object. I had an illustration of a hammer, which seemed to be a simple shape, with no weird inside parts or sharp corners. I started by opening the vector file in Inkscape.

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Once I had the file open I used Inkscape’s dynamic offset feature to extend the shape into a larger piece so I’d have “walls” for my mold.

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I did a Boolean difference between the original and the scaled part to get the wall piece, with the wall pieces being approximately 4mm wide.

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I also created a bottom plate that the wall piece would attach to. I did not make it fit with pins or any other alignment method, I just ended up using tape to hold the pieces together.

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Here are the modeled pieces. The wall piece was easy enough to flex around, but seemed strong enough to hold up for the casting.

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And here are the printed pieces. The flexible filament did not print as well as PLA does, and there were some rough parts on the top of the walls, but it wasn’t going to matter for these purposes.

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I put the two pieces together and applied some masking tape to hold them. Since I was going to use plaster I knew that it didn’t have to be too water-tight to hold the plaster in place.

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I then filled the vessel with the plaster. (Yeah, I have a big bag of plaster on hand for weird reasons, so I occasionally use it, though eventually I want to use concrete for these experiments.)

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After letting the plaster dry for a few days I removed the tape and then pulled off the bottom…

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…and then was able to flex the wall piece enough to get the plaster out of the mold, so that worked pretty well. Again, this was not a complex shape, which really helped as I just had to push the piece straight down through the mold.

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And here’s my (tiny) plaster hammer. I like how it turned out. The edges are not perfect, but then, what is, Right?

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I ended up making two of them, and with one I found that it was fairly easy to shape the edges using tools, so my 2.5D hammer (sort of) became a 3D hammer.

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