Universal Parametric Spool Holder v2

Largely inspired by http://www.thingiverse.com/thing:283656, but also by http://www.thingiverse.com/thing:971275 and http://micro3dfans.com/download/file.php?id=100&t=1&sid=dd6a0187c45290eb48d930511e0b8567, this design attempts to iterate forward a fraction.

The primary change over the original inspiration is the inclusion of space for 2mm washers either side of the bearing in order to fully trap the bearing but also preventing any friction from a connection with the side of the box. An furthertweak here is the inclusion of space for an additional washer designed to keep the reel on place centered on the bearings.

Consideration is given to ease of printing, and in this respect, the design should print very well and, at least at 4mm thick edges (which you might change), will be tough enough not to move. It would be good to round off a number of edges and fillet corners, but the motivation escapes me for this.

Once I've completed a print, I'll add in the additional positional wa