This is an upgrade to the Ultimaker2 3D printer for people who have spools that do not fit the original spool holder, and spools that are too tight and thus do not feed smoothly, causing under-extrusion.
It is composed of two assemblies: a replacement for the filament guide and a replacement for the spool holder. Both utilizes ordinary skateboard bearings to achieve smooth rotation. The conical shape of the spool holder allows for any sized spool to be used, easily swapped because it uses a wing nut.
Files are available on YouMagine. I want to emphasize that I am sharing the STEP files, not just STL, because STL are harder for people to import and modify than STEP files. SolidWorks files are also provided.
The cross section images shows you how to assemble the upgrade parts. The screw diameters are #6 for the filament guide and 5/16″ for the spool holder. Please figure everything else out from the cross section images.