This design is a two-in-one: You get 1) a “Spool Holder” design so you can suspend your filament spool almost directly above your printer and 2) a “Filament Guide” design so you can guide up to 11 3mm wide filaments from the source spool(s) to printer(s) that are not directly below them without becoming tangled. If you want to, you can view a Youtube video going over the design at https://youtu.be/lbf3fEUWACU
Features of the Spool Holder:
1) You can very easily attach and detach it (see 4th picture).
a) If your board has slightly tapered or rounded corners on the side closest to the spool holder, then it’ll probably be so easy that you can use the side of your forefinger to put it on (even if you do it in the same location where you see my finger in step 2 of the 4th picture).
2) There are two chamfered holes for Spax construction screws in case you want to ensure it can’t be accidentally knocked off and damage any printer(s) below it.
3) While it’s designed for 1kg spools, I made sure it can hold more than 10 kg for more than a minute without any damage (also to try to guarantee no damage to any printers that might be below the spool holder). You can see it holding up 6.63 kg (1.5 gallons of water + 1 kg) in the 5th picture or 10.5 kg (2.5 gallons of water + 1kg) if you watch the end of the video.
4) Very lightweight: it only uses 5m (14.9 grams) of filament.
Features of the Filament Guide:
1) You can very easily attach and detach it (see 4th picture. It’s the same mechanism as the spool holder, but even easier since it’s not as thick).
2) All edges that strands might touch have a 45° 0.5mm chamfer to reduce plastic loss and friction.
3) The entire 85mm wide gap below the 10 guide holes can be used to separate the vertical-to-horizontal transition from the left-to-right transition to help the strands move with less friction and immediate restriction.
a) When using it to align strands from the spool, be sure to attach it “upside-down” so the wide hole is above the 10 strand holes (see the MS paint diagram).
4) Supports both 1.75mm and 3mm filament (all gaps for strands are at least 6mm wide).
5) It can keep up to 11 filament strands apart. You can also use paper clips to increase this number (up to 28 for 1.75mm filaments).
6) Very lightweight: it only uses 1.3m (3.9 grams) of filament.
Prerequisites for this spool holder and filament guide design: you’ve already made 3D Printing Nerd's filament shelves (link: https://www.youtube.com/watch?v=u19MeZWK1mw)... or you’ve securely suspended 1x2 boards above (but not necessarily directly above) your 3D printer(s).
To give credit where it's due:
* I wouldn’t have made this if it wasn’t for 3D Printing Nerd’s design competition.
* I used a similar attachment mechanism as MartinMajewski did in: https://www.thingiverse.com/thing:1832235, but I did not measure his creation or anything (not that it would have helped).
* I would not have been able to make such a good design without Prusa and all the people who came before who made 3D printers fairly cheap, reliable, easy to assemble, and bug free.
* My coworkers who helped me take pictures and loaned me an empty spool holder.
* Others known and unknown who taught or showed me things I used to make the design (e.g. Mr. Dent, my “Statics and Particle Dynamics” teacher in college).