This is a modular spool for 3D printing filament which can hold multiple filaments in the same spool. If you're like me, you have several samples lying around without spool; this is an attempt at storing them in an orderly fashion.

The model consists of three logical parts, the screw, the nut, and the separator (by which I mean the plate where you attach the endings of the filament. Is there a technical term for this?). Combining these parts gives modular segments that can be screwed onto a main screw axis to create separate compartments for the filament. It's easy to customize the design to make your own spool; I provide two configurations for 1 and 3 compartments, on a 75mm and 93mm spool.

The separator has pre-made holes to accommodate the filament; two close to the nut external cylinder and eight on the most external ring. The holes are made in the two possible winding directions of the filament, to avoid bending it too much, and can be used to "sew" the filament through.

• External diameter of the screw: 54mm (-0.2mm of tolerance)
• External diameter of the nut cylinder: 58mm
• Diameter of the separator: 160mm
• Diameter of the internal hole (inside the screw): 42mm
• Thickness of the separator: 3mm
• Screw pitch: 8mm
• Screw lead: 32mm (the screw has 4 starts)
• Gap between the threads and the nut: 0.4mm (each screw and nut are shrunk by 0.2mm). This is already included in the model! The gap is 3-dimensional, i.e. 0.4mm is the distance between the two surfaces along their normals.
• Diameter of the filament holes: 4mm
• Filament holes: 5 clockwise and 5 counterclockwise, (10 in total), of which 2 located close to the nut and 8 alternated along the external ring of the separator.

Possible improvements === I have noticed that the nut cylinder is relatively small in diameter compared to retail spools. This winds the filament a bit too tight, so it tends to have some "spring" effect. This surely could be improved by makin the nut cylinder larger.

Some pre-made configurations ====

Measure your spool holder bar before printing!!

75mm spool, 3 slots

• 1x `Separator-Screw-72mm.stl`
• 3x `Separator-Nut-24mm.stl`

75mm spool, 1 slot

• 1x `Separator-Screw-72mm.stl`
• 1x `Separator-Nut-24mm.stl`
• 1x `Nut-48mm.stl`

93mm spool, 3 slots

• 1x `Separator-Screw-90mm.stl`
• 3x `Separator-Nut-30mm.stl`

93mm spool, 1 slot

• 1x `Separator-Screw-90mm.stl`
• 1x `Separator-Nut-30mm.stl`
• 1x `Nut-60mm.stl`

Customizing the spool ===

Download `Part-Separator.stl`, `Part-Screw.stl`, `Part-Nut.stl`. You can combine those parts to obtain compartments of custom sizes. Of course you can also trim down the existing 90mm screw or 30mm nut and that would work just fine.

The separator has a inner hole of 42mm of diameter, so that suits perfectly the screw, but you may need to remove part of it to assemble it together with a nut (the inner part of the hole needs to be threaded).

The screw and the nut parts are exactly 8mm in height, that is, they are one single pitch of the screw, so you can just duplicate them to obtain any length (not only multiples of 8mm), since the screw cross section is the same curve (rotated while extruding along the axis).

An idea for customization could be printing just the screw without separator, and then screwing nut-separators onto it. This would allow to reassemble arbitrary spools on the same screw.