Replacement bearings for print 2622 auto-rewind-spool-holder-for-mmu by Martin

This allows you to save your steel bearings for a project that needs them. Printed roller bearings are sufficient for this light duty task.

Print instructions

Replacement bearings for print 2622 auto-rewind-spool-holder-for-mmu by Martin

Nozzle 0.4 mm
Material: PLA

Files: gcodes for three filament manufacturers and MK3 & MK3/S printers.

You only need one of these gcodes. Hover and select the one that suits you best.

Print time: Under two hours.

This allows you to save your steel bearings for a project that needs them. Printed roller bearings are sufficient for this light duty task.

Make sure your print bed is clean before this print. There are many small print-in-place parts that must stay in place.

The weighted arm bearing does the least work and for this a drop-in replacement 8x22x7 bearing (608 size) is provided. This is the trickiest bearing to print as, using a 0.4mm nozzle, at the thinnest only two strands of plastic hold the rollers together.

The two rod bearings need to be stronger: by incorporating the bolt part as an extended stub axle room is made for thicker rollers. You no longer need the bolts. The bearing with the '+' mark is meant for the cogged end.

The bearings will print seized, DO NOT FORCE THEM. If you try to free them by force they will break.

To free the bearings:
Take a strong needle, a sewing needle will do for the 8x22x7 bearing but the others require something stronger. Insert it into the hole in each roller in turn and wiggle it to free the rollers one at a time. You may have to try several rollers before you can free the first one but once one is free the others have room to move and become easier. When you have freed them all; it is best to go round twice, gently rotate the bearing by hand and check that all the rollers are turning freely. The bearings will be rough at first but they will run-in quickly as you turn them by hand.

The bearings should just slide in place and fit by interference. If one is too tight check there are no surface flaws and sand gently if necessary. If the bearing slips out a dab of glue will hold it.

To run-in the bearings quickly: assemble the rod with the bearings and fit a filament spool. Mount the rod on the frame without the arm and spin the spool for a few minutes in each direction. Remount the rod with the weighted arm and check the rewind action when you feel the motion is smooth.

...and the fourth bearing, the one used as a weight? Sorry, there is no replacement here BUT: The weight, about 11g, can be anything you have to hand. It is worth trying different weights as the force required varies according to the length and route of your filament run. You may find that the spool holders farthest from the MMU need a heavier weight than those closer.