The vast majority of 3D printers out there today are FFF (Fused-Filament Fabrication) printers that make parts out of plastic. But you’ve probably also read news stories about more exotic 3D printers that are used to print food, concrete, and even biological tissue. Most of those move in the same way as your typical FFF 3D printer, and the difference is in the extruder mechanism. Instead of feeding plastic filament into a hot end, those 3D printers use a special extruder that pushes material out of a syringe. Justin Atkin has taken advantage of that idea to build a cake-decorating robot.
Atkin actually has more ambitious plans for this robot than just decorating cakes, and hopes to eventually use the same basic design to create synthetic opal and for bioprinting. But those are expensive endeavors, which is why he wanted to test to design first by dispensing frosting onto baked goods. Because the movement is conventional, just about any 3D printer or CNC setup can be used. The unusual part of the robot is the extruder. For that, Atkin used a syringe extruder design that he found on Thingiverse.
The plastic parts of the syringe extruder were 3D-printed by a friend of Atkin’s. The metal parts can be purchased online, but Atkin chose to machine them himself from steel and even titanium. After assembling the mechanical parts and adding a stepper motor, Atkin set the extruder up be controlled by an Arduino through an EasyDriver stepper motor driver board. The whole extruder was then mounted on a CNC machine for movement. Right now the extruder and CNC machine don’t talk to each other, and the extruder just continues to push the syringe down to dispense frosting during the whole “print.” But Atkin plans to eventually expand the robot’s capability and get to bioprinting and printing opal.