Stepper-driven paste extruder for Delta-type printers

This is a stepper-driven paste extruder for delta-type printers, specifically the Rostock Mini. It is the result of a collaborative project at Port City Makerspace in Portsmouth, New Hampshire to build a 3D printer that prints using chocolate. It was heavily inspired by the ceramics/clay extrusion work of Jonathan Keep, though we have since moved away from his pneumatic extruder design.

There are many paste extruder designs out there already. Although some of them reportedly work pretty well, none of them seemed ideal for our use. The goal of extruding chocolate - the kind that hardens, not frosting or ganache - presented some unique technical challenges, especially keeping the material hot while extruding. This would make extrusion over a tube difficult (for temperature control reasons). We also wanted to avoid mounting the stepper motor on the effector, to keep the weight lower, since we were using a delta.

The result is a flex-shaft driven extruder. It is precisely cont