This Universal Spool Holder will work, set on a table, for any printer but is really designed to be hung on a Prusa i3 MK2 or MK3.

As all Original Prusa i3 owners know, the spool holder that comes with the printer is pretty rubbish. There are many alternatives available here on Thingiverse but none of them would handle all of my needs. This spool holder will:

• Support large (over 2Kg) spools
• Allow a heavy spool to roll freely
• Fit any size (width) spool
• Handle two (or more) spools for quick colour change mid print

• Hold loose "sample size" coils of filament
  The left support has left-hand threads and the right support has a right-hand threads. This allows you to screw both ends together at once (obviously, one end of the rod has a left hand thread). Near the ends of the rods there are small flat sections so you can use a 6mm wrench to tighten the rods. As the rods are printed flat, the threads may be less than perfect. I've included a left-hand threaded nut that you can use as a die to clean up the thread if necessary. I assume you've got a normal metal M8 nut laying about for the other end.

  I've included two rod lengths; the 235mm rod is the longest that fits on a Prusa, the 165mm rod will be a little stiffer and is long enough for two standard 750g spools. You will need to print two of whichever length you choose. I've also included an optional left support with a right-hand thread in case you prefer to use a metal M8 threaded rod rather than printing plastic ones.

  The bearing holders are designed to fit #608 (8 x 22 x 7mm) skateboard / fidget spinner bearings. You can buy a pack of ten on eBay for less than £3.00. In truth, roller bearings are overkill for this application so I've include optional bearing replacement disks to use instead. You will need to print 4 bearing holders (and, optionally, bearing replacements), 8 if you want to be able to hold two spools at once.

  The support legs have a hole wide enough to pass a USB plug for cable management.

  If you are planning on using this on a table, you may want to print a third rod for the back feet to add a little rigidity to the unit.

  The supports and bearings are up high enough that they won't interfere with the extruder even when Z = 200mm (see photo).

  There is an optional loose filament hanger that simply clips onto the rods https://www.prusaprinters.org/prints/7945-loose-filament-holder

  You may also be interested in my Filament Guide/Oiler https://www.prusaprinters.org/prints/7944-filament-guide-oiler (works with any spool holder)

Print instructions

The rods are printed flat (with a flattened bottom) so you need low layer height for the rods. The rest can be printed at 0.20 to save time.

I used E3D's MatX (ASA) which is as strong as ABS but without the warpage problems. PETG should work OK too but I don't know about the rods. PLA would be to brittle.

Post-Printing

Screwing the first rod into the supports is straightforward. For the second rod each ends screw into the supports simultaneously. If you are facing the printer, hold both supports against the appropriate end of the rod then turn towards you.