I'm fan of spool holders mounted to the side of printer. However all the designs out there are fixed and occupy space next to printer no matter if it's in use or not. I had to fix that.

I'd love to see your make - please publish :)
Consider a tip if you like my work :)

Inspired by great design of HugoHuge (http://www.thingiverse.com/thing:3020026) I designed more compact spool roller (with hidden bearings) and most of all foldable. Thanks to double arm mechanism the spool roller moves always horizontally. Foldable roller eases putting on spool with filament.

Spool holder is designed to handle 1 kg spools of 200 mm diameter and up to 78-80 mm wide.

It can be mounted to any printer build on 4040/4020 V-Slot profiles: Creality, Geeetech, Anet, Alfawise, Zonestar, Tronxy, etc.)

Here's how it works: https://youtu.be/K1N113E6E5w

Print settings:

• Print orientation: as original SLTs (you can still print mount up right but it may not withstand forces and break along layers)
• Supports: only for mount and carriage - for best strength
• Material: ABS, PETG (optionally PLA, especially for arms as it's very stiff material)
• Layer height: 0.3 mm (0.28/0.32)
• Shell: 4-5 walls (1.5-2.0 mm) for arms & mount, 3-4 walls for other parts
• Top/bottom: 4-5 layers (1.5-2.0 mm) for arms & mount, 3-4 layers for other parts
• Infill: 20-30%

Hardware:

• 608 bearing (outer diameter: 22, inner diameter: 8, width: 7) It's very popular link
• 3x M3/M4 8 mm bolt
• 3x M3/M4 T-nut (M3 T-nut adapter is here)

Sand pins a bit if fit too tight into holes.

Assembly:

1. Insert bearings into slots in spool
2. Put spool into case and insert shaft through hole from either side
3. Put hinge in carriage and secure with hinge pin
4. Put arms in carriage and secure with carriage pins
5. Slide hinge into case
6. Screw mount to profile near the its end with 3 bolts and T-nuts
7. Put arms in mount and secure with mount pins

Check out my other designs:
https://www.thingiverse.com/DaVinci2000/designs

The little filament spool visible in image and video can be found here: http://www.thingiverse.com/thing:3755275