[DIY] Dry Box for 3D Printing Filament

A rite of passage in the 3D printing hobby world: making your own filament storage dry box !

The goals for this build are:

• Up to 4x 2.2lbs (1kg) spools
• Spool size up to 8" diameter x 2.75" width (200x68mm)
  
• Access to each individual roll without disturbing the others
• Stable guiding of the spools, both when full or near empty
• Desiccant storage independent from the spool carriers
• Small footprint

Several DIY projects out there provided inspiration for this design. Especially Marsgizmo's Filament Bunker

As well as the very refined Anybox from 3D Print Files

And Crosslink's DryBox V2

Thank you all for sharing your experience and designs with everyone 👍

Of course one can't ignore the Rolls Royce of them all. Behold the in-the-works open source Filament Changer Bay (a la AMS, ERCF, MMU...) from Construct 3D. It is a multi-filament changer + dryer + soon-Hot Plug/Unplug solution, compatible with most spools up to 3.5kg 🤯 

Brilliant ! Am sure it'll just cost a penny too 😅 Demo at 4:33 in this video. 3D STEP file here.

This said, one could instead simply go with an alluring in-line filament dryer, like Filadry or Thorndsen 3D. Stellar reviews. Go for it 😂

Though to be fair, an industrial solution like Drywise might work better. But at over $2000 one could buy 3 Bambu Lab P1S high speed printers and simply feed them all with my ~$40 drybox, ha !

Meanwhile, back on earth... the Sterilite 20 Qt / 19 Liters Gasket Box perfectly meets my goals listed above, for $13. It is airtight thanks to its lid gasket, and can barely fit 4 spools, resulting in a pretty small footprint. And it is tall enough to provide space for desiccant trays under the spools. Great start !

Accessing spools independently ruled out designs based on a rod running through the center of the spools. Although that is a super simple design, it requires taking all the spools out of the box to do anything. Instead, I went with rollers mounted on a carrier for each spool. The bearings are just the ubiquitous 608 8x22x7mm skateboard bearings.

The carrier geometry was optimized to reduce the risk of spool wobbling / escaping / lurching while unwinding. Hence the position of each roller far out and high, almost at the edge of the spool, to lower the center of gravity of the spool relative to the contact points on the rollers. And the tall vertical arms at each corner help guide the spool when it is prone to teetering, especially when it is almost empty and light.

Note the tongue on the right side of the carriers. It keeps the spool further away from the box's wall where the filament exits. That decreases the max and min angles the pulled filament starts and ends at while unwinding, from full-spool (filament farthest away from core) to empty (filament closest to core).

The desiccant tray is a simple ~1.5" tall box with ribs to provide a stable platform for the spool carriers. The front and back ribs are slightly raised such that the carriers sit snug within, preventing them from moving forward when the filament is pulled.

Finally, the pass-through holes in the box for the filament were drilled lower than the height of the spool's core to provide a downward stabilizing force on the spool once near empty. 

Many designs put these holes high in the box which has a tendency to lift the spool up. That works pretty well only until the spool is close to spent. At that point, being 2.2lbs lighter, it can easily lurch up / forward if there is any filament tangle, or when the bent end of the filament that is hooked to the core catches at the very end.

With all these parts printed, time to add some Reusable Alumina Desiccant or Pure Silica Gel Desiccant, install the pneumatic bulkhead union fittings, plug in some 4mm OD PTFE tubing, and TaDa! a completed dry box we now have.

Finally, to monitor the humidity in the box and know when to recharge the desiccant via a heat cycle in the oven, a humidity meter can be used. Like the excellent $16 AcuRite 01083M that provides high accuracy measurements and actually supports the full 1-99% Relative Humidity (RH) range. Unlike most cheapos out there that don't reliably go below 20% RH. That's pretty key when some sensitive filaments require around 10% RH to print smoothly.

The CAD & print files are available here, with a choice of several formats: F3D Fusion 360, Sketchup, STL, STEP, etc.

And with that, endless hours of 3D printing fun now await us.

Happy printing to all !