250 Gramme filament spool adapter for Eibos Polyphemus

Spool cheeks to enlarge a 250 gramme spool so that it works in the Eibos Polyphemus dryer

This is all about wishing to dry filament on small spools (250 grammes) typically those supplied by Sunlu in their multi-spool bundle packs

e.g.Amazon codes, TPU = B0DYVDW1B6, PLA+ = B0FSXGWHVN, PETG = B0FH9LFB15, ASA = B0FJX45C3H.

I have the Eibos Polyphemus dryer, which has the excellent feature of rotating the spool throughout drying to give a much more even result, however the rotation is delivered through the rims of the spool and the little 140 mm diameter 250 grammes spools fall between the drive roller spacing and rest on the base and so do not rotate. The dryer is designed for 210 mm diameter spools (usual for 1KG filament) [it also does larger].

Rather than try to design supplementary rollers which looked a fiddly option I have designed supplementary spool cheeks, that can be fitted to the small spools and ride the rollers for full functionality.

My design thoughts. I worked throughout with OpenSCAD. The cheeks must be open mesh to allow maximum passage of dry air for moisture removal. Fixing the cheeks to the filament spool should be easy. I considered many ways of making two core boss pieces that clicked together but were removable and fully re-useable, and reasoned that the mechanism would be awkward and to print it would almost certainly require supports with all of their implications, so I just went for a big screw thread. Its been reliable for a few centuries (invented circa 400 BC by Archytas of Tarentum) so good enough for me.

The two parts of the core boss therefore thread together and the outer diameter is 50mm to be reasonably safe to fit inside most spools. To take up any slack (just for satisfaction really, its not mechanically essential, but does ensure that the spool remains balanced and minimises any bias on the rotation rollers) I've included a collar. The one provided fits the 250 gramme Sunlu spool, YMMV so you may need to make your own. Its a very simple open ended cylinder and can probably be created without a CAD program by using slicer facilities (Prusa slicer can certainly do it). The collar serves to keep the cheek tidily against the flanges of the core bosses. I am indebted to Ryan A. Colyer for his http://www.thingiverse.com/thing:1686322, threads_v2p1.scad, thread library.

I printed in PETG for toughness, the spool cheeks print slightly flexible. If you feel the need for a stiffer result then perhaps move up the filament scale, but its just a utility device. no need to go over the top into CF territory.

Both Spool core bosses and the collar were all plated at once (using Prusa slicer). I used 0.2mm Structural print adjusted to Vertical shells with 3 perimiters, Horizontal shells with 4 top and 4 bottom layers, Infill 20% Rectilinear, with a standard PETG filament profile, 0.4mm HF nozzle. My print time was 1 hr 55 min. I used a satin print sheet, the PETG stayed put during printing but simply lifted off once cool.

Spool cheeks do just fit the sheet. The open honeycomb effect was achieved entirely in the slicer, the STL is just a simple flat disc. I used 0.2mm Structural print again but adjusted to, Vertical shells with 5 perimiters, Horizontal shells with 0 top and 0 bottom layers. This allows the Infill of 10% Honeycomb to form the entire body apart from the rim and centre. If you feel you can trust me then the bgcode file (or the translated gcode file that you can read if you're twitchy) will work on a Prusa Core One and print the cheek without you needing to re-slice and fiddle with the slicer settings. Print time 1hr 1min each (2 cheeks).

Images show the two cores, angles chosen to show the threads, the collar, and the g-code version of the cheek (the stl version is just a solid disk so not useful). The assembly diagram is a cheat, promulgating a honeycomb to create it in OpenSCAD was fun! (I didn't use the OpenSCAD honeycomb to make the stl.  I have provided the Stl of the final assembly but it will NOT print as it is several parts, however the stl will allow you to see a rotatable view of the final exploded assembly.

So one cheek fits the core boss that has internal threads, followed by the collar. The other cheek fits to the shoulder of the externally threaded core boss. The spool of filament takes the collar and then the other cheek and boss screw in to just hand tight (where the layer lines actually help a secure tightening). Pop it in the dryer and away you go. Please enjoy and tell your friends (I need the points). Thank you, Polymath April 2026.