Modular & Minimal Filament Drybox (with no bearings required option)

Update (27 March 2025) - Uploaded a new thread only (no sides) universal spool holder axel at a user's request. This allows you to use two female ends and adjust to any size needed. See the "Drybox Axel - 50mm Universal Threaded (Male, threads only) v05" file (in the Special Requests folder).

Update (8 Feb 2025) - Uploaded a new universal spool holder design that is threaded and will not get caught on the arms. See the "Drybox Axel - 50mm Universal Threaded v05" files.

Update (8 Feb 2025) - Revised the arm to prevent the spool holder from getting jammed. This includes a chamfer and guide rail that prevents the corners of the spool catching on the arms. This will become the new default arm (in the Latest Files folder). I also added a version with screw holes that go through the arm (in the Special Requests folder).

See additional updates below.

My take on the cereal box-based filament drybox. I looked over many of the other designs available and found them to be overbuilt and lacking flexibility. Key features of this design are:

• Hanging or standing spool design. Take your pick. This design supports wither hanging the filament from the lid or have it stand upright. Either way, this design is better than using a roller system in the bottom. The filament can easily get bumped off the rollers to become dislodged when in use. The hanging or standing design keeps it in place no matter the orientation or however much you shake the container. Once assembled, it is rock solid.
   
• Minimal hardware requirements. This design requires four M3 screws (and washers) and two 608 bearings. Other designs required more parts, which I see as unnecessary and add to the cost without any meaningful benefit.
   
• Minimal filament, maximum strength. Some of the existing designs are massively overbuilt for a 1kg spool of filament. This design uses very little filament but is very strong due to its design. I tried to remove filament where I could (witness the holes in the spool holder) in order to save on cost and print time. 
   
• Modular and expandable. You can easily add or remove components to this design. Add or remove the hydrometer bracket. Expand it by adding an additional bracket based on your own design. And if you have different size spools than mine, you can easily modify the spool axle to fit whatever brand you use. 

I prefer to have desiccant loose in the bottom of the container so I can clearly see the color (i.e. if it needs replacing). I started to design a bracket to contain the desiccant, but I decided it wasn't needed. Having it loose also makes replacing the desiccant as easy as pouring it in/out. If you prefer a container, let me know, and I may add it as an option. 

Change log:

Update (15 Nov 2024) – Fixed an error in the arm which caused the shaft that goes into the bearing to be out of round by 0.3mm and lengthened it to 12mm make it less prone to slip out of the bearing. I'm also adding a universal threaded spool holder that does not require bearings. This adds a bit of friction to the spool holder, so it doesn't prematurely unwind the filament due to the rotational mass of the filament spool overpowering the bearing friction. 

Update (15 Oct 2024) – Added two new frames – one hanging, one standing - for round hydrometers (42mm opening).

Update (12 Oct 2024) – Added two universal spool holder designs. One is threaded with angles sides so it can accommodate a range of spool hole sizes and widths. Just screw them together to sandwich the spool between the sides. The other holder is fixed width (70mm) with a deep-set axel that should accommodate any spool with a hole of 50mm or greater. With this design, the spool loosely “rides” on this spool holder. I prefer the threaded version, but I thought I'd give you all a couple options. I also adjusted the bearing hole slightly, so it is easier to insert the bearings. 

Update (23 Sept 2024) – Added a 62mm axel option along with 62mm and 72mm “deep” axels with optional spacers to accommodate narrow filament spools. Multiple spacers can be added to fit any width spool. 

Update (22 Sept 2024) – Fixed an error in the 60mm axel CAD models that caused them to print as two parts. 

Update (4 Sept 2024) – Added additional axels for different size filament spools (50, 53, 55, 58, 60, and 72mm) and added frames to enable it to stand up rather than hang from the lid. 

Update (25 Jan 2025) - Uploaded a modified arm with a 4.5mm spacer at a user's request. See the Special Requests folder. 

Update (25 Dec 2024) - Uploaded two threaded spool holders that are slightly wider at 77mm and 80mm for wider Extrudr filament spools. Please note that the 80mm version may not fit all containers or will be a tight fit. See the Special Requests folder. 

Update (23 Dec 2024) - Uploaded a set of 66mm spool holders. See the Special Requests folder. Also tweaked the arm based on feedback (made screw holes slightly smaller/tighter and enlarged the bearing shaft slightly).

Update (14 Dec 2024) - Uploaded a longer 149mm arm that is 25mm longer (requested by another user). See the Special Requests folder.

Update (3 Dec 2024) - Uploaded an updated threaded universal spool holder. The threads should be easier to print, and I refined the design to minimize the amount of filament needed. I also added a bearing-less version with detents so it won't unwind prematurely. See the image with the blue spool holder.

Assembly instructions:

• Standing option: For the standing version, the container is used upside down - the frame stands on the lid and the container goes on over the top. To assemble, use either of the standing frames depending on whether you will use a hydrometer. I recommend using flat head screws (button head are next best option) if you have them as the frame holes are angled so you can countersink them.  Drilling holes in the top is optional as it will stay in place without them. 
• Hanging option: If you are using the hydrometer bracket, place it in the top of the container and drill four M3 holes where the holes are on the bracket. If you are not using the bracket, you can position the arms up against the bump-out for the pop-up opening. You can mark the holes and drill them from the top side.
• Screw the M3 screws directly into the arms – or, if you are using the hydrometer bracket, feed the screes through the top, then the bracket, and into the arms. The holes in the arm are sized for the M3 screws to thread into them snugly. I recommend washers to protect the plastic container top. 
• For the spool holder (axel), the 608 bearings should press right into the ends of each spool holder. If your prints have bulging at the bottom (i.e. “elephant's foot”), you will need to ream the edges, so the bearings can slide in. You can get them started by hand and then flip it upside down and press it down onto a surface to fully seat them flush. The two axles then slip together. It's a loose fit since the container and arms hold everything together. There are three spool options - two universal designs and a set of different sizes to match specific spool sizes. I recommend the Universal Threaded design as I think most people will like it best. Send me a note if you need a different size.
• To insert the spool and axel assembly into the arms, just flex the arms apart slightly and inset the spool. The arms should fit in/out the bearing easily. If not, give them a light sanding. Otherwise, the spool will be too difficult to remove. And a tight fit is not required as the container sides keep it all together. 
• The hydrometer pops into the opening on the hydrometer bracket.

Parts list:

• Cereal storage containers: https://amzn.to/4f6PgdU
• 608 Bearings: https://amzn.to/4ffYrJe
• Hygrometers: https://amzn.to/46iyXXw
• M3x12 screws and washers (hanging with hydrometer bracket)
• M3x8 screws and washers (hanging with no hydrometer bracket)
• M3x8 flat head screws (standing) 
• Desiccant: https://amzn.to/3YgGhkA
• Bowden couplers: https://amzn.to/3A3yBI3

Printing:

• Any filament is okay to use. I use Inland PLA+ from MicroCenter, and it is more than strong enough. 
• No supports. The only area to watch for is the hydrometer bracket opening, but it printed fine on my Ender 3 Pro without supports. So, you shouldn't need them.
• 15-20% infill is recommended. 
• 3 top/bottom layers recommended.
• 4 walls recommended.