Machine-top spool holder for Printrbot Jr.

A spool holder that fits on top of the z rods of the Printrbot Jr. This holder works well and minimizes the footprint of the machine. (It looks good too, in my opinion.) The holder consists of a stand and two cylinders that are fixed with screws underneath the stand. The cylinders fit on top of the z rods. A two-part hub is mounted in the spool with protuding axles that rest on the stand. The two hub parts slide into each other. The hub design may need to be adapted to the spool dimensions. Sour