Universal Dry Box (NO hardware required) - With DAD Jokes!

UPDATE December 9, 2024:  I modified the Onshape project to make the the Swirly-Hub-Things™ more free floating.  This does not really affect the downloadable files here, but makes the parametric hub spacer thing on the project a bit nicer.   I also updated the cover pic because I like the Swirly-Hub-Things™ facing in the direction shown.  They do work in either direction though.

Got wobbly, hardware-heavy dry boxes that are full of holes?  This 100% 3D-printable design is hub-centered, easy to assemble, and works universally with standard 1kg filament spools and has no screw holes.  Just print, assemble, and keep your filament dry!

Most dry box designs rely on roller systems where the spool rides on its outer diameter.  I’ve never liked that idea—what if it tips over?  Spools are meant to spin on their hubs.  Plus, I’m not a fan of buying extra hardware to make it work.  That’s why I created a fully 3D-printable solution that’s stable, easy to assemble, and hassle-free.

Now, while this may have taken some inspiration from other projects I have seen around the internet, the design is my own from the ground up, using Onshape.  I don't know that I can really call this a remix, though some initial inspiration did come from the "Modular & Minimal Filament Drybox" by tcosta:

https://www.printables.com/model/983885-modular-minimal-filament-drybox-with-no-bearings-r

I had a few issues with that design though.  The base didn’t fit snugly into the container lids, leaving gaps that allowed slight movement.  My biggest gripe, though, was needing to print different spool hubs for every spool size—definitely not ideal.  I wanted something more universal.  At first, I considered making the legs adjustable to vertically center the spool using an undersized hub.  Eventually, I came up with the Swirly-Hub-Things™ you see in the pictures.  They work great! The spools stay centered regardless of hub diameter or weight, and the Swirly-Hub-Things™ keep their springiness even after months of compression.  That said, while I’m calling this design “universal,” it’s best for standard 1kg spools or others with a similar form factor.  Wider spools could probably be accommodated with a larger food container, but other parts would have to be adjusted as well.

I also couldn’t get on board with drilling screw holes into containers—it’s just asking for air to leak in.  That said, these containers aren’t exactly going to hold a vacuum to begin with, so don’t expect laboratory perfection.  I did try, and this is probably as good as it gets for a food storage container meant for Froot Loops and oatmeal.  I often remind myself, we’re not building rocket ships here.

SWIRLY-HUB-THINGS™: These I am very proud of, the stars of the show! They should be printed laying down with ALL PERIMETERS or whatever your slicer's equivalent of Cura's "concentric infill" is.  Use 100% concentric infill for these.  Print with DRY PETG or something similarly flexible, I would avoid PLA and other rigid materials.  As designed they should reliably hold any spool with a hub diameter of up to 90mm.  Initially I designed the bearing version, all the while thinking it was overkill (we're spinning a spool at revolutions that are better counted by the HOUR!) and sure enough, when I mounted one, I found that the bearings barely spun at all, just rotating around the stationary axle while scarcely turning on their own.  I redesigned and went with the bearing-less design I present here.  I still included the bearing version for those striving for NASA-level perfection.  I'm telling you, bearings are NOT necessary for a dry box.  The bearing versions obviously won't go as small as the non-bearing versions, but they still fit every spool I have come across.

BASE:  I tend to dislike seeing facets on prints, so I will probably always upload larger, high polygon count STL files …  That said, I uploaded a lower polygon count one that should work just as well.   Other parts are pretty reasonable in size even with the higher poly counts.

SPACERS: For the Swirly-Hub-Things™ to work optimally it is a good idea to put some spacers, both inside the spool between each Swirly-Hub-Thing™ and on the outsides between the legs and the Swirly-Hub-Things™.  The idea is to get things so there is little space for lateral movement of the Swirly-Hub-Things™ along the axle.  Do not make things tight; you still want a millimeter or two of play so the hub can spin freely.  Print what you need (I provided various size spacers to achieve the spacing you need.  That said, the design does work without any spacers.  With spacers, though, I can be pretty rough with the filament box, dropping it on the floor, shaking it around violently, maybe even kicking it down the stairs and the Swirly-Hub-Things™ stay attached no matter what.   For those who would rather do things a little more cleanly, what I do in the Onshape project is adjust the SpoolWidth in the variable table, which adjusts spacers programmatically to the exact length I need.   I then export those and print them out.   If you go this route, and you choose the bearing versions of the Swirly-Hub-Things™, you will want to adjust the SwirlHeight to 7mm (or your bearing width) as well, but don't forget to adjust it back afterwards, or you will be left with some really thin Swirly-Hub-Things™ ...

FEEDER: I also uploaded lower poly versions of these files.   I sized the hole to fit the 25 feet of PTFE tube I purchased online.  The threads are optimized for a 1/2" (12.7mm) drill bit, and the 1.5mm thickness of the food containers.  For the washers, make sure to print those out in TPU or some other flexible material.  The one for the nut is different than the one for the bolt.  It has a bit in the center that goes up into the lead-in chamfer on the nut.  Make sure you mount it in the correct direction.

LEGS AND PINS.  Make sure to print TWO of each of these things, or else the whole thing will be one-legged, and probably won't work very well.  When assembling, it is easiest to put the curvier side of each leg into the base first, and only a few millimeters at that.  Once you have both sides into their receptacles, push them down, and the geometry itself will hold them in nice and snug.  Once you have everything assembled, you want to push the pins through the legs and into the axles.  They should go all the way in, as they do in the pictures.

CAP: The cap/plug thing is used to keep air from getting into the box via the PTFE tube.  Print this in a flexible filament as well, the softer the better.  I have been using 95a TPU for them and they work fine.  A little grease goes a long way toward sealing things up nicely.

GASKET RISER: Honestly, I haven't even tried these yet but you may want to give it a try.  The idea is to place it under the silicone gasket that comes with these containers, raising it up a little so as to require a little extra "smoosh" to get things sealed more tightly.  Flexibles here would probably be best.

SLICING: The rest of this is pretty standard drybox fare.  Print each part in the orientation shown in the slicer preview.  I generally don't bother with supports on the nut and bolt, but do for the top of the receptacle for the hygrometer.

THINGS YOU WILL NEED:

FOOD CONTAINERS.  As I said above, get the kind with the three ridge things on the narrow end.  They are very common on the internet under a plethora of brand names.  The base should very TIGHTLY fit into the lid of those 4 liter (yes, I am an American) containers with the three vertical grip things on the narrow side.  They are available online under quite a few no-name brands, Praki and Skroam seem to be the main ones I find as of this writing, but I am sure they are available under many other monikers as well.  Make sure you get the kind with the THREE VERTICAL RIPPLY GRIPPY THINGS ON THE NARROW END.  They usually come with these water-based white ink/black surface labels that work pretty well.

HYGROMETERS.   These are somewhat optional.   I buy those cheap-o rectangular hygrometers that usually come in packs of many.  They are all the same, packaged across the internet under another plethora of different brands.  They do seem to have a limit of about 16% or so, as I put three of them in my kitchen food dehydrator at 120°F for about 6 hours and they never dropped below that.  I am guessing these boxes are well below that number.

PTFE TUBE, 4mm/2mm.  I got a roll of 25 feet for cheap.  It's what I will continue to use and you can't stop me.  That said, it does feel a little tight.  If I were to buy again, I might look for something with a little bit wider of an ID.  It's also available in plethoras.

DESICCANT.  I like to put a metric ton of desiccant at the bottom of the food containers, keeping the air inside dry for quite a long time.  So far, on the first one of these I made, I have not even bothered to recharge it because it has stayed bright orange for something on the order of 3 months now, and the hygrometer is still happy.  I have also opened it up twice to change filament rolls, so it is now on its third roll without needing recharge.  Make sure you put the base and legs in first, or you may have a hard time getting it all together, and you will DEFINITELY have desiccant beads all over the place.  I originally filled desiccant up right to the brim of the lid itself.  This resulted in a few little messes, so I raised the sides of the base a bit, but still use the same amount of desiccant.  No more mess.

I have provided STEP FILES for those who want to play with the design, and if you like Onshape, here is a link to the project itself.  Feel free to do terrible things to it!

 https://cad.onshape.com/documents/f75204ccc3cb49206024ae48/w/91a90ad0fb5164513c885fe5/e/fb579b8aebba00074c9d9249?renderMode=0&uiState=673cfaa450d2eb53f6a4b720