Fusion 360: Finger-jointed tray for laser cutting

This is a parametric finger-jointed tray intended for cutting on a laser cutter. The number of fingers automatically adjust based on an "optimal" finger width (specified in the fingerw parameter), and the dimensions of the tray.

The fingers then resize themselves to be as close to the "optimal" finger width as possible along all three axes, but they will deviate from that size if necessary to maintain at least 3 fingers along each edge.

**Version 11:** Updated with a parameter (ldividers)