Coiled Shells is a system for generating custom G-code for a 3D printer. Inspired by the radial symmetry and diverse shapes produced by diatoms and other sea creatures, a single continuous curve is generated with stepwise z-motion within Grasshopper, and then converted into G-code.

The final G-code generation system supports hollow 3D print volumes while eliminating the need for infill, allowing for the overhang and overlap necessary to print delicate symmetrical forms.