Yet Another Drybox

Why Yet Another Drybox Design?

I was looking for a storage solution for my filament, but the popular designs I found weren't right for me in terms of size or didn't meet all of my needs. I finally found some storage containers on Amazon (see parts list below) with perfect outer dimensions, so I started designing the necessary parts to turn it into a new drybox design.

What is special about this box?

• It has a small footprint of only ~46cm (width) x 26cm (depth). This means it fits in  a cupboard (inside width ~46cm), can be stacked in a row (one behind another, which takes ~53cm) and of course stacked on top of each other.
• A filament path with an angled filament outlet that does not require additional space to allow for this stacking.
• With this small footprint it still offers a capacity of four spools of 1kg filament. Alternatively, 5 smaller filament spools will also fit.
• Special caps for the reverse bowden tubes, with labels and a gripping mechanism that prevents the filament from slipping back into the tube.
• The angled path of the PTFE tube allows for a bit of "pull back": When the filament is changed in this reverse bowden tube setup and a few cm of filament is pushed back into the PTFE tube, the PTFE tube retains a bit of tension on the filament and it will not loosen around the spool.
• Mechanically adjustable, bearing-based spool pulley assembly with hygrometer mount and silica storage container
• Of course it's stackable, airtight, looks good and is over-engineered ;-)

Placing and Stacking Options

The main feature of this box is that it can be stacked tightly and fit into a 50 cm wide cabinet (outer dimensions). Besides of vertical stacking (picture 1) it can also be stacked one behind another. And as the filament outlets are angled they perfectly support this type of alignment (picture 2 and 3).

In my setup the boxes are placed above the printer (picture 4 and 5) with the PTFE tubes being guided though an outlet in the shelf board which allows me to directly access the filament of all three boxes for printing.

If you want to place the box aside of your printer, you can also mount the filament outlets accordingly (i.e. rotated by 180° and a bit further to the bottom) with the PTFE tubes then guided upwards. I did not build such a box yet, but I do not expect any issues with the pulley gantry. If you have built such a box, maybe post a make and give the dimensions of where you placed the outlets.

Multi-model project and where are the files?

I decided to publish two components of this drybox design as a separate model. Just click on the links to get to the files and the detailed description:

• Pulley and M8 Threaded Clips for Filament Rollers 
• PTFE Tube Cap with Filament Label

The reason for this is that the two are pretty universal and could be of use for building other dryboxes and I think it will be easier to find if it's released separately.

Also you most probably want to print additional Silica containers that go into the center of the filament spool. This will allow you to keep the air in the box dry for a longer time, easily replace some Silica gel when changing a filament spool, and also it will add weight to the filament spool which makes it roll even more robust on the pulleys (especially if the spool is almost empty). The ones which I used for in this project are Filament Spool Desiccant Canister.

The Parts , Howto Print and What You Should Know

Let's go through the parts list, let's look at some specifics and how they should be printed. For my boxes I printed everything in Prusament PETG with a layer height of 0.2 mm and I will also provide gcode files for printing on a MK3s+.

• Baseplate: These fit into the corner of the drybox and allow mounting of the brackets for the threaded rods. The base plates compensate for the box's curved bottom and it becomes a rattle and wobble free seat without the need for anything being glued. Type 2 is just the mirrored version of Type 1. You will need two of each type.
  Print Orientation: Place the top side on the printbed
  Supports: Manually add some support along the recess for the brackets. If you just bridge these gaps, the mounts will not sit flat and the hygrometer mount will not fit perfectly either.
  Perimeters: 4
  Infill: 30%
  Required Quantity: 4 (2 of each type)
• Brackets: The hole for the rod in the bracket should already have enough spacing for the threaded rod. If your print doesn't, take an 8mm drill bit to clean it by hand. Make sure the bars go really smooth, otherwise the assembly will be a pain.
  Print Orientation: Place it upright
  Supports: None
  Perimeters: 4
  Infill: 30%
  Required Quantity: 2
• Filament Outlet: The angled filament outlets are (almost) airtight. It also has room for an optional small sealing O-ring to further increase air-tightness
  Print Orientation: Place the plates it with the flat surface on the printbed
  Supports: None
  Perimeters: 6
  Infill: 30%
  Required Quantity: 5 (one will be used as a drilling guide)
• Hygrometer Mount: This part can be mounted on the right bracket (as it is not symmetrical; if you want it on the left side, just mirror it in the slicer). To have it inside the box definitely isn't the best option in terms of readability but I opted for this as it works for me and I wanted to avoid cutting to many holes in the box. If this is a concern for you, you can find several mounting options for this hygrometer that fit right into the box's wall.
  Print orientation: Place it with the front-facing side on the printbed
  Supports: None
  Perimeters: 3 
  Infill: 15 %
  Required Quantity: 1 
• Silica-Container: It requires quite a bit of filament to print and also requires some space on the print bed (it fits on an MK3s but takes up almost the entire bed). Also, it doesn't hold a lot of silica gel, which is a bit of a price to pay for the box's small footprint. But it works well and adds a professional touch to the box. If you don't want to print it (or it does not fit on your printbed), you can also choose to only use the filament containers that fit inside the spools.
  Print orientation: Place the container upright on the printbed
  Supports: None
  Perimeters: 4
  Infill: 20 %
  Required Quantity: 1
  Note: To print it on a MK3S+ You need to remove the skirt in the slicer as there is no space for it left on the printbed. And if you do not mind the extra time, use ironing for the flat surfaces.
• Silica-Container Sidebars
  Print orientation: Place them updside-down on the printbed
  Supports: None
  Perimeters: 3
  Infill: 15%
  Required Quantity: 2 
• Silica-Container Side-Cover
  Print orientation: Place them updside-down on the printbed
  Supports: None
  Perimeters: 4
  Infill: 15%
  Required Quantity: 2 
• Silica Container Center-Cover
  Print orientation: Place them updside-down on the printbed
  Supports: None
  Perimeters: 4
  Infill: 15%
  Required Quantity: 1 
• Silica Container Refill Cap
  Print orientation: Place them updside-down on the printbed
  Supports: None
  Perimeters: 4
  Infill: 30%
  Required Quantity: 2 
• Silica Container Refill Funnel
  Print orientation: Place it updside-down on the printbed
  Supports: None
  Perimeters: 4
  Infill: 30%
  Required Quantity: 1
• Pulleys and M8 Clips:  Check the Printables Project Page
• Filament Tube Caps and Labels Check the Printables Project Page

Required Parts

The following parts are required for one Drybox and 4 filament spools. 

Building Your Box

Getting everything ready

There is not much to say about this step. :-)

Let your printer do the work and remove the support afterwards. In the meantime, get all the other parts you need. You might also want to check out some additional silica containers that fit into the center of the spools (the ones printed in blue).

For a complete box, your setup should look like the picture.

Pulley assembly

Start by making the pulleys and after pressing the bearings in, I recommend wrapping the printed wheels in Heat Shrink Tube. All the details on this (and also to get details for the M8 clips which we will need in later steps) can be found on the separate model page: Pulley and M8 Threaded Clips for Filament Rollers

Gantry bracket assembly

You will create two holders for the threaded rod consisting of:

• 4 Baseplates (2x Type 1, 2x Type 2)
• 2 Brackets
• 1 Hygrometer Mount
• 4 M6x16mm hexagonal screws, nuts and washers

Place the hygrometer mount on the top right corner (keep in mind that it is not symmetrical). Insert the nut into the slot on the underside of the base plate. While holding the nut in place, place a washer on the M6 bolt (optional and not shown in the pictures), feed it through the end of the bracket and mount it onto the base plate. The screw should only be tightened slightly so that the bracket can be moved on the base plate for final adjustment (later and in the box). Do the same with the second base plate, just without a second hygrometer mount. Repeat the same for the second bracket. Check that everything fits well into the box.

Gantry assembly

• Cut the M8 threaded rods to 33.4cm
• Make sure the threaded rod goes easily through the holes in the brackets. If not, clean out the holes by hand with a sharp drill bit.
• Put 6 pulleys (for a box for 4 filament spools) on each threaded rod (there will be two additional pulleys on each rod, one on each end).
• At each end, mount the brackets as shown in picture 3, add another pulley and place the flat nut on the outside. Don't tighten everything just yet.
• After doing this on all 4 ends it should look as in picture 4.
• Place the assembly in the box and check that everything aligns. Take it out and tighten the nuts on the threaded rod.
• Take a sample filament spool to check how you want to align the gantry inside the box, you will have a couple of cm to play with. I decided to move the gantry all the way to the opposite site of where I planned for the filament outlets. (Picture 6)
• Tighten the nuts to fix the gantry as shown in the last picture.

Pulley positioning

• There are different type of clips: Use the center clips for in-between two pulleys and the side clips on the outside. Note that the side clips have an orientation.
• There is a small center clip (pictures 2 and 3) and a wider center clip (pictures 4 and 5). If you do not mind the few millimeter of space, I recommend to use the wider one so that you have a bit more space between the spools and also for the optional silica containers inside the spool.
• Take a filament spool and place it on the fixed pulleys on the outside. Now move the other pulleys where they need to be and lock them with a side clip (on the spool's “inside”) and a center clip; move the neighboring pulley to the center clip and use again a side clip to hold it in position. Result should look like in picture 3 and 5.
• Do the same with the rest of the pulleys. In the center of the rod you can fix the pulleys just with side clips as shown in picture 6.

It will depend a bit on the spools you want to put in the box if this setup (one center clip in-between two pulleys) works for you. For 4 spools of Prusament (or similar) it works perfectly. But just print some spare clips and test a bit yourself. The main idea of the clips is that it is easy to rearrange the pulleys without the need of reassembling the complete gantry.

Filament Outlets - Drilling the Holes

• Mark the positions of where you want the filament outlets. Picture 1 - 3 will show you the exact measures that I used for all my boxes which I am happy with.
• Note: You can also place them with the outlet directing upwards if e.g. you want to place the box aside of your printer.
• Drill two 4mm holes for each filament outlet (where the screws will hold the two plates).
• Mount a spare filament outlet as drilling guide and drill the center hole for the PTFE tube (picture 3 and 4). Use a 5mm drill bit.
• Picture 6 shows how things should look like at the end of this step.

Filament Outlets - Assembly

• Place the O-ring in the PC4-M10 PTFE hose connector (optional). (Picture 2 and 3)
• Mount the hose connector to the printed filament outlet. (Picture 4)
• Mount everything on the box. Make sure for the correct orientation of the inside plate!
• At the end things should look like as in picture 5 and 6.

Making the Box Airtight

• Just follow the pictures to add the sealing tape. It should sit slightly above the brim of the box so it air-tightens the box also where the handles are (picture 2 and 3).
• Guide the PTFE tubes through the outlets. If you have trouble getting them through the outlets, loosing the screws of the filament outlets for this step will help.
• Apply some lubricant to the seal for the lid to easily slide over the sealing tape. (Picture 5)
• Put the lid on. It will be quite tight at the first time, but the seal will adopt over time and it will go easy after a day. It also helps to push the sides of the box towards the center while closing the lid.

Prepare the Silica Containers

• Place the M4 nuts into the sidebars. (Picture 2)
• Place the sidebar on the underside of the tray. (Picture 3)
• Use M4x8mm screws to mount the sidebars to the tray. (Picture 4)
• Clip on the lids on the tray before filling it with Silica gel. It will be really difficult to do this with the Silica gel in the tray as this will get in the way! So, clip on the lids first….
• … and then fill-in the Silica gel using the funnel. You will see that there isn't really a lot of space for the Silica gel to move while filling the tray (especially in the side compartments). But placing the tray on a flat surface, filling the funnel about halfway, and then quickly “shaking” the tray will do the job in a minute and the gel should not jump out-off the funnel.
• Close the lids with the printed cap.
• Optionally fill the containers which go into the center of the spool. The additional weight will help the spool to roll while the filament gets less and the spool lighter over time. Especially if you use Prusament spools, check out the once I used as they fit perfectly: Filament Spool Desiccant Canister

Put the Filament Into Your Box

• Put your filament spools into the box and guide the filament through the PTFE tubes.
• Place the handles on the ends to grip the filament to make it airtight.
• Print some filament sample labels with the filament which is on the spools and clip it on. You will find the handles and caps for different filament types on the project page: PTFE Tube Cap with Filament Label

DONE :-)

Proudly look at your box, grab a beer (or whatever you like) and if you like the design and the detailed documentation maybe think about buying me a coffee.

Some Remarks and Attribution

Before I designed my parts, I played around with Anybox V2 from Marian. While my box is a bit of over-engineered, the Anybox is a great and cost-optimized box, with perfectly designed parts and documentation. So if my box doesn't fit you, checkout the Anybox which might be better suited for you. Thanks also to Marian for allowing me to share some modified parts for non-commercial use.