This is a work in process.  The top seal needs a beveled grove to hold the o-ring.  I planned on fixing for the past couple years but I have not.  Because this has been a draft for so long, I decided to publish.  If there is enough interest, I may add the grove.   In the mean time, RTV holds the o-ring in place.

NOTE: End the end, I decided to just buy a dry box.  That would be my recommendation.  If this is useful to you great, I don't plan on ever updating it.

This design is not directly based off of any other designs.  I did look at a lot of drybox designs before making this so there could be some similarities to other designs.  This was designed in OpenSCAD as that's my design program of choice.  Enjoy!

Disclaimers:  

• Use this drybox at your own risk for your filament.  I didn't leak test it but I believe it is fairly airtight.
• You should print a 50mm Silica Gel / Desiccant Container https://www.thingiverse.com/thing:3494496 which can stay in the filament spool
• I have used many Inland (Microcenter) filament spools and they have all been compatible with design.  I make no promised your spool will work!
• See above statement about the o-ring groove.

Printed parts:

You'll need to print the following parts.  The included files are for 0.4 nozzle and 0.6 nozzle.  I printed with the .4 nozzle but a lot oof time can be saved with the 0.6 nozzle.  I included the .3mf files so change to your preference. 

• Spool holder (see separate section, This is the spool holder included with Prusa Mini)
• Knob
• output tube clamp
• Bottom Right hand
• Bottom Left hand
• Top Right hand
• Top Left hand

Knob:  

The knob is designed to work with standard ¼ hardware.  I typically purchase from Bolt Depot but probably any ¼ hardware will work.  You'll need supports when printing.  Once you print remove the supports and press in the ¼ bolt.  The ideal length is 1.25" but 1" may work and longer will be usable but annoying!  If you don't use my gcode, you should either print solid or print solid in the section that holds the bolt.  With Prusa slicer this is easy!

Output tube clamp:

This is attached after the output PTFE tube is installed to hold it in place.  You don't have to use it as it should be a tight fit but it's recommended.  I printed solid as it's very small and also needs to be strong.  You could print with less infill and it should be fine.

Bottom Right hand:

This section includes the output PTFE tube and latch with ¼ nut used to secure the top when assembled.  Additionally (8) M3 nuts are pressed in to secure the bottom pieces together and for the PTFE tube clamp.  You can print at low infill (15-20%) but selective 100% infill around the (9) nut pockets and the entire latch area.  Supports are required for the output tube, spool holder rails, and for the latch.  The O-ring flange has a 45 degree angle and should print good on all printers.

Bottom Left hand:

This section includes the hinge and uses (6) M3x12 screws to attach the other bottom section.  You can print at low infill (15-20%) but selective 100% infill around the (6) screw pockets and both hinge areas.  Supports are required for the hinges and spool holder rails.  The O-ring flange has a 45 degree angle and should print good on all printers. 

Top Right hand:

This section includes the latch used to secure the top when assembled.  Additionally (8) M3 nuts are pressed in to secure the top pieces together.  The latch has a clearance hole for the knob to connect to the nut in the bottom right hand nut.  You can print at low infill (15-20%) but selective 100% infill around the (6) nut pockets and the entire latch area.  Supports are required for the latch.  The O-ring flange has a 45 degree angle and should print good on all printers.

Top Left hand:

This section includes the hinge and uses (6) M3x12 screws to attach the other top section.  You can print at low infill (15-20%) but selective 100% infill around the (6) screw pockets and both hinge areas.  Supports are required for the hinges.  The O-ring flange has a 45 degree angle and should print good on all printers. 

Assembly:

Print all the parts and order or acquire all the “parts to order”.  Remove all supports from all printed parts.  Build the spool holder based on the liked Prusa instructions.  Then follow these instructions:

• Prepare the top of box first.  You'll need (6) M3 nuts, (6) M3x12mm screws, and (1) ¼x1.25" screws. You'll also need the LH and RH printed box sections and the knob.

Parts to order:

I will provide links to all the parts I have used.  You can find other sources as there are many places.

Caulk/RTV:  https://www.lowes.com/pd/GE-Advanced-Silicone-2-2-8-oz-Clear-Silicone-Caulk/5001887997 (Not sure what I used but something like this will work)

1/8" O-ring  cord: https://www.ebay.com/itm/264293016139 

¼-20 nut: https://www.boltdepot.com/Product-Details.aspx?product=2648 

¼-20x1.25" bolt:  https://www.boltdepot.com/Product-Details.aspx?product=196 

M3 nut (alternate):  https://www.boltdepot.com/Product-Details.aspx?product=4783

M3 nut: https://www.boltdepot.com/Product-Details.aspx?product=4773 

M3x8mm screw: https://www.boltdepot.com/Product-Details.aspx?product=6379 

M3x12mm screw: https://www.boltdepot.com/Product-Details.aspx?product=6381 

Bearing (20 pack for 5 spool holders): https://www.ebay.com/itm/303031031081 

Bearing (8 pack for two spool holders): https://www.ebay.com/itm/302648951035 

PTFE tube: https://shop.prusa3d.com/en/minimini/1084-hotend-ptfe-tube-mini.html 

Silica Gel: https://dryndry.com/collections/silica-gel-beads/products/half-gallon-orange-dry-dry-premium-desiccant-indicating-silica-gel-beadsindustry-standard-2-4-mm-3-7-lbs-reusable 

Spool Holder:

Assemble per Prusa instructions at https://help.prusa3d.com/en/guide/6-spool-holder-assembly_204973.  This will also require (4) 608 bearings, (4) M3 nuts, (4) M3x8mm screws, and (4) M3x12mm screws.  Do not install the antislip pads as described in the instructions.   Alternatively you can use the spool holder that shipped with your Prusa Mini if you remove the anti-slip pads.  The plastic parts can found at one of the below links. The first one includes instructions and the second is a direct link to the files.  You'll need to print (4) MINI-base-spoolholder.stl and (2) MINI-rail-spoolholder.stl.

NOTE:  To follow the instructions entirely, you may need to visit: https://www.haribo.com/en-us/products 

https://www.prusa3d.com/prusa-i3-printable-parts/ 

https://www.prusaprinters.org/prints/57214-original-prusa-mini-printable-parts