I found that some filament spools, particularly ones without a raised inner lip, would catch on the standard T-shaped Prusa MK3S spool holder.

This was a 2 hour project to quickly improve the situation.

Goals

• Reduce friction in the system
• Use the existing base (cut down on waste)
• Keep one arm unmodded (works fine for most of the filament I use)
• Use hardware I happened to have on hand

Required Hardware

• 2 x 4mm x 86mm (length) smooth rod
• 4 x 3mm nut
• 4 x 3mm x 14mm (length) bolt
• 2 x 4mm (hole) x 8mm (outer diameter) bearing

Misc

A few things that can easily be improved:

• Trim down the rod to the exact length needed (I left it at 100mm)
• Experiment with using only a single smooth rod or 3 smooth rods
• I decided to glue the spacers onto the rod to prevent any horizontal movement. Alternatively, the spacers could be resized to cover the full length of the rod.