MMU2 Redesigned Reinforced Drum

thingiverse

The idler drum on the MMU2 is secured to the motor's shaft by two screws going through two square nuts. These nuts ensure a sturdy connection, but be cautious not to overtighten them, as I learned the hard way when my first drum broke during the initial build. When in use, the drum can become loose, requiring you to tighten it again. However, this process can lead to breaking the drum once more. To avoid this issue, I've implemented a standard drive-gear attachment system that utilizes a set screw embedded in metal. This design allows for a smooth sliding motion of the gear into the drum without removing any pins. For easier access when tightening the gear into the machine, it's recommended to insert the gear with the screw-side facing towards you. A warning: The initial version of this design is quite tight and may require forceful insertion, which could result in splitting the drum. Those who have attempted it recommend heat-setting the gear into the drum for a secure fit. A new, looser version has been created, which fits better and seems to center more accurately. The drive-gear used in this design features a 12mm outer diameter with 22 teeth and a 5mm shaft bore.