Eight-Section Expanding Pizza Divider, 13 in Closed
An expanding pulley mechanism rebuilt from six sections to eight — a 3D-printable divider that opens evenly from a 13-inch closed diameter.
The client had found expanding-pulley designs online, built a rough prototype, and hit the limit: every available design has six sections. They needed eight, to divide a pizza evenly.
The problem
Going from six to eight sections is not a matter of adding two more:
- The whole mechanism is angular. Six sections means 60° per segment; eight means 45°. Every link length, slot angle and pivot position changes.
- Expansion must stay even. If the segments do not move together, the slices come out unequal — which is the one thing the product exists to prevent.
- A 13-inch closed diameter was fixed, so the mechanism had to fold into a defined envelope rather than sizing itself.
- It had to be 3D printable, which limits how thin the links can be and how the pivots can be made.
The approach
- Rebuilt parametrically from the segment count, so the geometry is driven by the number of sections rather than adapted from a six-section layout — the reason existing designs could not simply be modified.
- Synchronised expansion through the link geometry, keeping the segments positively coupled so they open together instead of relying on friction.
- Sections sized for FDM printing, with pivot features that survive layer adhesion and clearances that work at printed tolerance rather than machined tolerance.
- Closed diameter as the driving dimension, with the open state falling out of the mechanism rather than being set independently.
The result
A working eight-section expanding divider, delivered as printable files converted to STL at the client’s request.
Where this applies
Iris, expanding and synchronised-segment mechanisms: dividers, apertures, adjustable frames. Segment count is the parameter everything else derives from — which is why these designs cannot be edited, only rebuilt.
I design parametric mechanisms that can be rebuilt at any segment count. Request a quote or see all services.