Airtight Dry Box for 3D Printer Filament

If you have done a bit of 3D printing at home, you probably know from first hand experience that moisture can ruin plastic filament, especially PLA. Over time, moisture in the air is absorbed, and this can cause issues ranging from reduced print quality, to complete print failure. In my case, I hadn't used my printer in several weeks. When I did use it again, the PLA first layer wouldn't stick to anything, it just balled up and got pushed around at the printer head. After weeks of trouble shooting, I bought a new roll of plastic and my printer suddenly worked wonderfully.

This dry box will allow filament to be used and stored over long time periods while remaining moisture free. Additionally it incorporates a filament filter, which will prevent any dust/dirt from entering the printer head, and optionally apply a bit of lubrication for easy successful printing every time.

NOTE: To recondition bad PLA, place a test piece in an oven at the lowest setting. It should get warm but not tacky or overly flexible (best to keep at/under 80 °C). If your oven goes this low, you may place the entire roll of spoiled plastic in there for 2-3 hours to recondition it. Alternately, store your spoiled filament in the dry box we are about to make, and after a week or so it should be properly dry.

Step 1: Gather Materials

A) Necessary Materials

- Storage Tote (Must be large enough to fit filament spools, minimum dimensions of 10 inches (260mm) was my requirement, that should fit spools larger than shown). Also available from Amazon but only as a 6-pack or at a very unreasonable price.

- Rubber Tape

- Silica Gel Desiccant

- Rod for spindle (~8mm x tote length), I had a piece of threaded rod left over from my RepRap build

- Super glue and (optionally) super glue accelerator

- Push-to-fit tube connectors for 3mm filament OR for 1.75mm filement

- Small pieces of foam

- PTFE tubing for 3mm filament OR for 1.75mm filament

B) Tools

- Power drill and bit set

- Sandpaper

C) 3D Printed Parts - These can also be found on my Thingiverse page

- Spindle Rod Holder (x2)

- Feedthrough A (Exterior)

- Feedthrough B (Interior)

Step 2: Make the Lid Airtight

Use 4 pieces of rubber tape to make a seal along the inner rim of the storage tote lid, overlapping the corners. First test fit a piece, cut it to size then apply to the lid. Note that this type of rubber tape is not especially sticky, except to itself. So after placement on the lid the tape can be repositioned, but when overlapping tape corners, it will be a bit more difficult to undo so try to make sure it fits well when overlapping the corners.

Step 3: Attach Rod Holders

Test fit the spindle rod with a spool of plastic filament on it to get the height correct. Take a piece of sandpaper and scuff the side of the box where the rod holder will be glued. Spread super glue on the back of the 3D printed rod holder. Press it onto the sanded spot on the tote. By looking from the other side of the tote (if yours is clear) you should be able to see how well the super glue is adhering, press to get as complete of coverage as possible.

You can apply the accelerant if you wish, but either way I recommend letting the glue dry for several hours, even better if it can dry overnight. Air and moisture need time to diffuse into the space between the two plastics in order to cure the superglue.

Next put the rod in the one holder that is attached, and align the rod so it is level to the other side. Repeat the sanding and attachment process for the other 3D printed rod holder. Once this is fully dry you can put the filament spools on the rod and place the rod in the holders.

Step 4: Prepare the 3D Printed Feedthroughs

Screw in the push-to-connect fitting to the 3D printed feedthrough. It is designed to be a snug fit, so it may help to warm the female plastic side slightly (with a lighter for example) before screwing the threads in. Make sure to keep the fitting aligned and straight. Test fit that is it straight by inserting a piece of filament through it.

Now cut a piece of foam to fit in the recessed part of the other filament feedthrough half as shown. Poke a small hole in the center to allow the filament to move through it. Test fit a piece of filament as shown.

Step 5: Add Filament Feedthroughs

Drill a hole a few inches from the top of the tote with a drill bit of slightly larger diameter than your filament. Test fit the filament and lightly sand both sides of the box wall for better glue adhesion.

Now apply glue to the faces of the 3D printed feedthrough parts. Be sure to keep some distance between the glue and the feedthrough hole and especially from the foam, which will soak up glue on contact. Center the pieces on the hole you drilled in the tote and firmly press the pieces on, with the tube fitting facing outwards and the foam sealed against the tote on the inside, with the access hole to the foam facing up. While the glue is still wet, you can test fit a piece of filament to make sure all of the holes are aligned. Be sure to move the filament in and out so the glue does not bond it in place if it does come in contact.

Again, accelerant may be added at this time. Be sure to let the superglue dry thoroughly. Overnight drying is recommended.

Repeat these steps for as many ACTIVE filament spools as you will need, usually 1 is enough but if you have a dual extruder set up you will need a second. Another option is to give each spool a feedthrough, then glue a second exterior only feedthrough near the bottom of the tote. Then when a spool is not in use you can plug that PTFE tube into the lower push-to-fit connection on the tote. This will make changing filaments quick and easy if you change them frequently, while keeping the dry box sealed.

Step 6: Prepare for Use

Add the PTFE tube to the push-to-fit connectors. These are typically used for Bowden type extruders, which I plan to add to my printer soon, but I will use the tube to guide the filament for now anyway. Feed the filament through the hole in the tote box and into your extruder.

Optionally, add a few drops of oil to the piece of foam within the feedthrough fittings. Some people suggest mineral oil, or vegetable oil. This will serve to further lubricate the filament as it travels through the PTFE tubing and into the extruder. I don't find it necessary for now, maybe in the future or with filaments other than PLA.

Add at least two packets of silica gel at this time. Add the lid and close it up. You are now ready to print with your moisture free filament!