Part 1 shows how to use parametric design to make the same design more universal to differing sizes without the need to re-do lots of measurements. 

In part 2 we create the filament spool which is driven by parameters so with just 5 parametric changes you can change the spool sizing to match yours.

Spool width, Spool diameter, centre hole diameter, inner wall-to-edge diameter and spool wall thickness

Part 3 is where all the awesome stuff happens. We create a single draw based on the spool diameter and it can auto-magically  change size to suit a different spool or number of draws required.