Adam Blumhagen's Hack Turns a 3D Printer Into a Rotary-Axis CNC Mill — for Carving Apples

Mechanical engineer Adam Blumhagen has converted his 3D printer into a rotary-axis CNC mill, for a somewhat unusual reason: To carve apples, in order to create patterned chocolate-enhanced goodies for an edible arrangement.

"I had this idea to cut designs into apples then fill them with chocolate to make something like an edible arrangement," Blumhagen explains by way of introduction to the project. "To do the carving, I swapped the extruder on my 3D printer for a rotary tool, and mounted the x-axis motor to the print bed, so I can rotate the apples as they cut. I used Inkscape-gcode tools for the gcode and Repetier-Host for the controller software."

Suitably converted, the modified printer turns the apple and uses a cutting bit in the rotary tool to gradually carve out the skin and a small section of pulp from the target apple. The cuts are precise, as you'd expect from a CNC system, though require manual finishing: "I found it much easier to use the tip of a knife to remove the cut pieces of apple," Blumhagen explains, "[rather] than having the CNC remove it for me."

Once removed, the gaps make up an attractive geometric pattern which can be enhanced — in both appearance and flavor — by the addition of chocolate. That step, however, proved challenging: "I melted chocolate and tried my best to pipe it into the cuts," writes Blumhagen. "This proved to be difficult.

"It didn’t stick very well to the apple’s wet flesh, but it did stick to the apple’s peel. I had to wipe off excess chocolate without removing it from the cuts. As the chocolate cooled, a large section would pull out of the cut as I was wiping. I wouldn’t call this a complete success or a complete failure, but it was interesting."

As well as a video showcasing the build in operation, Blumhagen has published a blog post on the topic — but has not yet released a build log or guide to converting your own printer for apple carving.