This is a reinforced version using a M4x30 screw in the center of the axle, so it should not be as prone to break as the original version. By not screwing it all the way in, you can adjust the angle of the axle towards the Mini-casing, so the spool is perfectly vertical. I added a slot at the end of the axle and a little slotted locking-disc that prevents the spool from falling off the axle. Printed and tested on my Mini, and it works very well. It was just a bit tricky to remove the support under the hook when printing the axle vertically, but with a good knive it's not that hard. 02.02.2014: Uploaded a version with a longer axle (74mm instead of 62mm that should work with 1kg spools. 18.06.2014: Uploaded another version that should work with the Up Plus printers. Check the comments for the details. (UP_Plus_Spoolholder_Axle_Reinforced_74mm_Long.stl)Printed the axle vertically at 0.2mm layer and 75% infill, the locking disc as well. The bearings were printed at complete fill, with minimal support (you need 2 of the bearings)