While my 3D printer, mini CNC, and laser cutter are wonderful tools, they are largely limited to plastic and wood for the machines I have.
Creating complex items out of metal with them has largely been out of reach, and my experience in that area has largely consisted of welding and fabricating items by hand out of sheet metal.
The world of casting items has fascinated me for a few years, but with some high barriers to entry and not a lot of practical projects coming to mind, I've mostly watched from the sidelines in various facebook groups.
A perfect storm came together, however, when Make Magazine Issue #75 contained an article on casting custom coins in pewter.
Pewter melts at a relatively low temperature, making it ideal introductory material, and the article described casting it into coins using molds cut and engraved with a laser cutter.
Shortly after, I came across a suitable melting pot on Temu for only $20, cheap enough that I need not justify it as anything more than a fun project to pass the time.
For my first attempt at a coin, I drew some coin faces in Photoshop and engraved them on two pieces of chipboard.
Following the instructions in the article, I sandwiched these around a laser-cut plywood body that would form the shape of the coin and a pouring funnel on top, and added holes and pegs for registration.
I melted down an ingot I got on Amazon and poured it into the mold once it melted.
The pewter solidified in the mould within seconds, and was cool enough to pull open (with gloves) in about a minute.
The initial resulting pieces were not great. Much of the detail was lost, and there were imperfections near the top of the coin. The first pours tended to have the poorest detail, which I guess may be due to moisture in the mold being boiled off and the mold otherwise being "seasoned".
Unlike 3D printing, laser cutting, or CNC milling, the great thing about casting, is that I could just put bad pieces back into the pot, remelt them, and try again with almost no net waste.
I cut a new set of coin molds and centers, experimenting with engraving depth, funnel shapes, and vents. I got better results on each new attempt, as was able to gradually improve my results with incremental improvements in both process and technique.
In the end, I found that it was important to make two engraving passes to have sufficiently deep engravings. Also, it was critical to heat up the pewter to a higher temperature than I did initially (enough that my existing laser thermometer went out of range) so that it would stay liquid after pouring long enough to settle in the nooks and crannies of the mold before it solidifying.
I added vents to try to improve surface texture, but later found they were unnecessary and just made the coins too difficult to remove.
For detailing, I like to color in the recessed areas with a brown sharpie, then polish off the high points with steel wool.
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