Spool Spacer for Bambu Lab X1 & P1S Rear Spool Holder - Reduces Spool Binding & Dragging on Printer Back

UPDATE 2025-06-07:     I noticed that some filament spools (Overture, etc.) have an open and ribbed ring around the center hole. I added a spacer that has two touch points to accommodate these types of spools.

This is a very simple, quick printing (1.61 gram, 100% infill at 0.12mm layer height) spacer or shim that is inserted in the slot at the back of the single spool holder on Bambu X1 & P1 printers. This spacer forces the spool away from friction points on the back of the printer, where spools can potentially drag and bind. This is particularly a problem on the X1 & P1S (I don't know if the P1Ps have this same issue), where there are sharp metal tabs that protrude beyond the back face of the printer, about 40mm above the mounted spool holder (see photos). As the filament is pulled, the spool tends to get pulled closer to the back of the printer until it rubs against those tabs. This occurs with all brands and types of spools, including Bambu.

This spacer eliminates this rubbing and replaces it with a single point of less resistance. It should work with all types of standard spools, including BambuLabs spools that have a gradual recess near the center hole.

I could be wrong, and maybe I didn't pay attention to the spool that much before installing this spacer, but it seems like the spools unwind more smoothly and uniformly with this spacer installed. It would be interesting to test this spacer on a large print farm, but alas, I own just one machine. 

INSTALLATION:     with the protruding touch spot facing out, simply slide the thinner portion of the spacer in the open slot that is formed between the back of the spool holder and the face of the printer back. It should insert right in, with a slight amount of friction resistance. The spacer can be installed or replaced in a few seconds. (See photo)

NOTES:

• The touch spot on this spacer is arced and rounded, so that there is minimal additional friction and drag, and it is much less likely that side ribs on a spool will catch on it. I recommend lightly sanding the protruding touch spot on the spacer with fine sandpaper to remove layer lines and to reduce friction. This can be done in less than 30 seconds.
• I don't know how long a spacer will last before wearing down. So, I printed my spacers with white PLA so that the spacer contrasts with the printer color and stands out. This will help me to remember to check it occasionally when changing spools. Since the spacer is so small and uses so little filament, I would print a few extra for spares.

Back story:     I was recently printing and noticed that the structural side ribs on the generic PLA spool that I was using would drag and occasionally catch on the back of my P1S (see photos). Then, when there was enough pull on the filament, the the spool would break free and click/lunge forward a bit. This was annoying, and it made me wonder if the extruder was being forced to deal with unwanted resistance. I designed this simple solution. It works. The same spool now rotates smoothly. Yay!