Update 2/9/2021 Added SpoolFastenerBig.stl per comment request with diameter slightly larger than 3" (85mm) for spools with such big holes. I have not printed it yet, but I think it should print without supports and should work. ALSO! mounting tape does not work great, it falls under the spool weight after a week. I have tried E6000 and superglue instead, both were easy to apply and are holding strong.

Update 1/18/2021 Confirmed the design works with the Rubbermaid 21-Cup Dry Food Container. Only change needed is to order a longer 100mm M8 rod. The result is a bulkier box, a bit more generic looking but fits well every spool I have on hand.

Update 1/10/2021 Added "slim" version of the Box Wall Mount. It works just as good but makes replacing the spool easier. I have discovered this works really well for the slimmer 0.8kg TPU spools but not so well for full-size PETG and some PLA ones. This is because of the indented profile of the cereal box I chose. Waiting on a different one (Rubbermaid) to arrive to test more.

I had a nitpick about all the available models, so I decided to design on myself. Key features:

• Cheap - under $17 per unit
• Minimal fabrication - the only drilled hole is for the filament passthrough
• Smooth spool rotation with bearings and firm grasping of the spool
• Humidity meter support
• Easy assembly options - glue (E6000 or superglue works great), holes for bolts

The parts are easy to print, all can be printed together as shown without supports. Only the nut grabbers need support. Those are optional but make the spool holder tightening nuts easier to grab and press again the bearing spacer to prevent rubbing.

IMPORTANT Some of the parts require good dimensional accuracy as the fit is tight, even press-fitted. This is intentional, but I recommend using -0.15mm Horizontal Expansion in Cura (or equivalent setting in other slicers). If still too tight and cannot be pressed in the plastic with pliers, you can scale up by half a percent or so depending on your printer.

The filament tube hole and the humidity meter can be mounted in different locations, depending on the specific need. How I did it works for a shelf behind and above the printer. For each set you will need to print two (2x) of the box wall mount, spool fastener, nut grabber

Parts used:

• Round hydrometer - https://www.amazon.com/gp/product/B07GR67G1M
• M8 hex nut - https://www.amazon.com/gp/product/B089PR8DVP
• 608ZZ bearing - https://www.amazon.com/gp/product/B00NX23HGQ
• PTFE tubing and coupler - https://www.amazon.com/dp/B07DC594D6

Bigger Rubbermaid - fits bigger spool sizes

• Rubbermaid 21-Cup Dry Food Container - https://www.amazon.com/gp/product/B00XJRMW5M
• M8 - 100mm rod - https://www.amazon.com/gp/product/B0819S15LP

Cereal Box - slimmer, better looking but only fits smaller 0.8kg TPU rolls

• Cereal Box - https://www.amazon.com/gp/product/B07HRKJYJF
• M8 - 80mm rod - https://www.amazon.com/dp/B07THYZ4DB

Cutting the hole is best done with a 20mm drill bit saw or some other similar tool. I had this set which worked great https://www.amazon.com/gp/product/B018QUQZY0 However for 1-2 units, can easily be done with an X-Acto knife or something.

Mount the rod holders are horizontally in the middle, vertically a bit higher than midpoint so it leaves room for the desiccant but it rolls freely with the lid on. See photos for examples.