3D Printed Molds For Casting Rose’s Metal

Have you ever played with Rose’s metal? It’s a fusible alloy of bismuth, lead, and tin with a low melting point of around 100 °C. Historically, it’s been used as a solder for cast iron railings and things, and as a malleable pipe filler material to prevent crimping while a pipe is bent.

[Ben Healey] has been playing around with Rose’s metal and some PETG printed molds, making everything from Star Wars Imperial credits to chess pieces to leather stamping tools. In the video after the break, [Ben] takes us through the process, beginning with mold-making from STLs — something he picked up from another YouTuber.

He recommends adding registration marks to multi-part molds in order to keep everything lined up, and adding a small recess in the seam for easy separation with a flat-head screwdriver. So far, the molds have held up to multiple pours, though [Ben] did print them rather thick and is glad he did.

As far as making liquid metal, [Ben] used a cast iron pot with a convenient pour spout, and a blowtorch. He added graphite powder to the molds in an effort to make them give up the goods more easily. To finish the pieces, [Ben] cut the flashing with tin snips and used sandpaper and a Dremel to smooth the edges. Copper plating didn’t work out, but [Ben] is going to try it again because he thinks he screwed something up in the process. He’s also going to try printing with TPU, which we were just about to recommend for its flexibility.

There are many ways to cast metal on the (relatively) cheap. Have you considered Kinetic Sand?

21 thoughts on “3D Printed Molds For Casting Rose’s Metal

  1. On a handful of parts? You’ll be fine. You’ve gotten more lead exposure soldering. This is a nice project, and perfect fodder for folks looking for something to pick at.

  2. (Second time posting this warning….)

    Using sandpaper and/or a Dremel is going to create a lot of dust. Rose Metal is around 25% lead. Creating lead dust is generally a bad idea and can lead to health issues, this is also illegal in some areas.

    1. Good note! Wearing PPE and sealing the parts after they are done are important. Also doing everything outside, and washing hands thoroughly too.

      Any sandpaper or things used should also be thrown away and not used for anything else.

    1. Depends where you live, as most of the cost is often from shipping stuff around.

      rotometals.com sells 65’C lead-free Field’s Metal, and I was happy with some other stuff we bought from them.

      when you leave the world of cheap plastics… things can get pricey very quickly ;-)

      1. If you can tolerate 138C you can just use 58% bismuth / 42% tin. Those are the cheaper of the component elements of field’s metal, which is half indium. I think some filaments will hold up to that temperature well enough to be useful. This is also a eutectic and available already alloyed.

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