Coil Bushing - Reduces extruder force

thingiverse

I've designed a bobbin holder for 3D printers with a smaller axis than the bobbin hole, allowing for various coil types. This offset causes more force on the extruder to pull filament. To fix this, I created a bushing that fits into the coil's hole, aligning its axis with rotation and reducing extruder force by nearly half. Calculations confirm this reduction. The design works because it lowers the moment of inertia, as shown in an attached image. This holder is specifically made for BQ PLA coils but can be modified to fit other types. I've included STEP and Catia CAD files for easy modification.