The Filaments.ca provided design for their EconoFil filament spool, while attractive, had one side which was significantly weaker than the other. This means it was a bit less suitable for filament spool holders which used the edge of the spool as its mounting method than the more common centre mounted ones. I built this design to more closely match the traditional spool design.

Despite the large cutouts on each piece, this version requires somewhat more filament than the filaments.ca version: 73.0m versus 66.5m for my printer and print settings. The centre of the spool holder is also slightly smaller than standard spools at 48mm (normal spools are usually at least 50mm), but a 50mm version is available if desired. Unless you need the extra space, I'd suggest using the 48mm to ensure the thread and inner walls of the inner part are sufficiently strong.

I've only tested this design with the PETG EconoFil filament, so it may not be suitable for ABS or PLA. I've also uploaded a square-ish version of the spool which fits square build plates which are at least 175mm. Obviously this version will also be incompatible with spool edge holders, but it does seem to fit my PETG spools, and works acceptably. I would strongly recommend using a filament guide of some sort (either a feed tube or just a ring) that keeps the printer pulling from the centre of the spool to prevent the filament from jumping over the edge (and tangling) when printing.

Features:

• More traditional spool design
• Indented filament loose end clips on the edge
• Cutouts for interior filament end (might prevent end-of-spool tangles if your spool has this end loose)
• Fusion 360 design file available for modification/remix
• Reduced size version available for <200mm print beds

The Fusion 360 file isn't the cleanest design ever, but if anyone wants to remix it themselves (or just to grab dimensions off to design their own), it's available here: https://a360.co/2s9pm2y

Note: This is not compatible with RichRap's master spool specification which uses a 102mm inner diameter for the filament bundle. EconoFil filament bundles seem to have a 77mm inner diameter, and their injection molded and printable spools both appear to use 75mm (which I'm also using here).