The ever-growing variety of 3D printing filaments is amazing — we can now print in strong, flexible, glowing, and dissolvable plastics — but sometimes plastic isn’t the right material for the job. Sometimes, you just need metal!
Although the big boys in the industrial world can directly 3D print metal parts with laser sintering machines, this technology hasn’t yet reached consumers. However, you can make your own metal parts at home with the help of your 3D printer and these easy-to-learn metal casting techniques.
ABS Molds for Bismuth Alloys
California artist Cosmo Wenman posted a tutorial on how to cast bismuth alloy parts directly into 3D-printed ABS molds (thingiverse.com/thing:26500).
Bismuth alloys (makezine.com/go/bismuth) have a lower melting point than bismuth alone (~212°F versus 520.6°F). This low melting point means a hollow mold can be printed in ABS and it won’t melt or deform when the molten metal is poured into it. After the metal has cooled, the mold can be split away or, for more complex objects, immersed in acetone to dissolve or soften the ABS so it can be easily removed, leaving behind only the final cast metal piece.
Some users are also experimenting with making two-part molds printed in plastics with higher melting points, like nylon. This allows them to cast alloys with higher melting points, like pewter.
NOTE: Many bismuth alloys contain toxic elements such as lead. Acetone is not a friendly substance either. Proceed with caution and follow proper safety measures when working with these materials. For a nontoxic bismuth alloy, try Field’s metal (see “Desktop Foundry,” MAKE Volume 35).
Lost-PLA Casting of Aluminum
A common technique in jewelry making and manufacturing is lost-wax casting or investment casting. A model or “pattern” is made in wax, then a plaster mold is made around the wax model. When the mold is fired in a kiln, the wax is burnt out or “lost”; then metal parts can be cast in the mold.
This same technique can be used with PLA filament. Jeshua Lacock of Boise, Idaho, used the lost-PLA technique and a homemade furnace to cast aluminum parts for his home-built CO2 cutting laser, going from design to print to metal part in just one day. He thoroughly documented the process at3Dtopo.com/lostPLA.
Backyard furnaces fueled by charcoal or propane can get hot enough to melt aluminum (1,220°F) and bronze (1,742°F). Engineers at Coreprint Patterns in Hamilton, Ontario, even used the lost-PLA method to cast stainless steel (2,750°F), taking their mold to a local foundry that could attain the higher temperatures needed (coreprintpatterns.com/lost-pla).
Sand-Casting Bronze from 3D-Printed Patterns
When QC Co-Lab (qccolab.com) opened the doors on their new hackerspace in Davenport, Iowa, they wanted to celebrate in style. They used their 3D printer to create commemorative medallions — and then cast the medallions in bronze using a homemade charcoal furnace and the sand casting method. There’s a great tutorial at Foundry101.com (foundry101.com/new_page_7.htm).
With these techniques, your personal desktop factory can help you create precious metal jewelry, aluminum parts for your robots, or bronze busts from your Kinect scans. The next time someone asks you, “Can you make metal parts with that thing?” you can happily proclaim, “Yes!”