Ultimate 3D Filament Dry Box With Auto Rewind.

First let me Thank cybrsage for his open source designs of the springs and to ikarisan for your open source design of the Temperature Humidity Meter Adapter plate. Both can be found on thingiverse.  

This is a safe and easy way to protect your 3D filament from open air moisture. With the auto rewind feature, the spool will re-roll itself daring retraction and filament changing. The auto rewind springs are designed for use with Bowden style printers (like mind) with a re-wind distance is around 250mm-300mm to allow full retraction of the filament between the extruder and the hot end. If you are using a direct drive I suggest pulling out about 200mm and letting it roll back up. Sounds strange but keeping too much tension on the springs will shorten there life span and the movement from the other spools could cause it retract your filament out of reach.

I have two ways of monitoring the temperature and humidity. The first one is with the Mini LCD Digital Temperature Humidity Meter and the second is with a custom built monitor with displays and lights. You will see the custom monitor in most of the photos. I will publish another build covering the custom monitor at a later time.

1- LCD Digital Temperature Humidity Meter

12- Precision Double Sealed Miniature Bearing-Steel

2lb- Reusable Desiccant Beads

1 (pack) PTFE Teflon Tube with PC4-M6 Pneumatic Fitting and PC4-M10 Straight Quick

As needed- PTFE Bowden Tube

14.5" - 5/16" Steel Threaded Rod

2- 5/16" nuts

1- 5/16" lock nut

6- #6-32 x 1-1/2" Machine Screw

6- #6-32 Nylon Lock Nut

12- #6 washers

1- 5-Gal. Professional Duty Waterproof Storage Container with Hinged Lid

1- 22" x 5" Plywood.

2- 1" x 2" x 5" wood posts

You will need to print one of each support. You only need one set of supports per box. Notice that one of the supports has an extra slot on the top for the lock nut to set in.

You will need one Grip shaft, one Spring, one Sleeve and one Spacer of each spool. This box can hold up to four standard spools. I have added a support ring if needed of wider spools. I have also added a cut-a-way of the center part of the spring to use as a tester for preparing the rod.

There is an optional Digital Temperature Humidity Meter Adapter plate.

This will be the hardest part of the build. In order for the spring to do it's job, the 5/16" Steel Threaded Rod will need to be flattened on one side.

Tape off the first 1 1/2" of one end, tape off the other end at 14 1/2" so that you have 13 1/4" of thread showing . With a file or sander (I used a table top belt sander) carefully sand or file one side flat. Be very careful to keep it as straight as possible. Flatten it down between the tapes until the thread just starts to disappear. Use the test ring to check you progress as you go. Be sure NOT to flatten the first 1 1/2" as this is needed to help lock the rod in place and keep from moving.

Once you have your rod ready, cut the rod to a total length of 14 1/4". By the way keep the cut off piece, it will come in handy later.

Installing the PC4-M6 and PC4-M10 Fittings. The top row of fittings is for the filament feed and the ones on the side are to allow a place to secure the ones not in use and keep the box sealed. I installed the M10's on the top as my feed out, These fittings do not have an internal stop and would allow the tube to keep going in and sense I don't remove them when changing filament. You could also use only PC4-M6 (I used this kit because is was the best price). Keep the top fittings around 3" apart with the first one about 3" to 3 1/2" from the end. Now install the other 4 on the side going up and down at about 1" apart or whatever works for and can be installed on either side. I chose the right side (Back) to keep them away for the busy side and out of the way. When you drill the hole make sure it is a little smaller than the fitting to make a good air tight fit. I used a 5/32" for the M6 and a 5/16" for the M10. You can also us a little teflon tape if you want.

The length of the PTFE Bowden Tube is based on your needs. It depends on how far away your box will be from your printer. I found that 28" (711mm) was perfect for me. It's long enough to reach the extruder and short enough to loop around and plug into the box to keep sealed. You can cut a piece about 1 1/2" to 2" long, plug one end with hot glue and use it to plug the open fitting or if you only have one box you can install 3 of the side fittings so you never have an open one.

Although I have not specified witch end of the box is the front or back it is very important to pay attention to the orientation of the spools and because the box can be turned to unload from ether side the support with the lock slot MUST go on the left side of the box (Tub fittings facing you) to insure the springs turn the correct direction.

Just to repeat, Although I have not specified witch end of the box is the front, it's very important to pay attention to the orientation of the spools. Because the box can be turned to unload from ether side, the support with the lock slot MUST go on the left side of the box (Tub fittings facing you) to insure the springs turn the correct direction. Turning the springs it the wrong direction will cause them to break easily.

The supports will not go all the way to the bottom of the box because of the inward slant. Put the top of the support 3" down from the top of the box. The bottom of the support will line up with the top of the slant. Make sure to check that both sides are at the same height. Keeping the rod level will help keep the spools from walking the rod when turning. Keep in mind the support with the lock slot must go on the left side (Tub fittings facing you).

Using 3- #6-32 x 1-1/2" Machine Screw, 3- #6-32 Nylon Lock Nut and 6- #6 washers for each support, Bolt the supports in place. Be sure to trim off the end of the #6-32 x 1-1/2" Machine Screw to prevent hitting the spools. I know you think glue would be easier but I tried that first and over time it failed due to the weight of 4 spools.

Now you can select witch end of the box you want as the front. I chose to put the box's to the left of the printer to keep it on the same side as the extruder. Using the LCD Digital Temperature Humidity Meter Adapter plate as a template, place it about 1" down from the top and cut out the center hole. The nice thing about the Adapter plate is that the meter fits great and makes mounting it so much easier but you can just make a hole and pop it in if you wish. Hint- if you use the Adapter plate now and you chose to use the digital monitor coming up in the next instructable, They have the same foot print.

You will need two Bearings for each assembly. Using the piece of rod we cut off, pass it through the "Grip shaft" and place a Bearing on each end. Using a 5/16" nut on each end, tighten then down until the bearings are pushed flush into the "grip shaft". After removing the rod, take the "spring" and snap it into the "grip shaft". Use caution, this is a tight fit and once you snap it together it can not be taken apart without damage. If you do find it necessary it can be glued back together (don't ask me how I know that ha ha).

It's very important to pay close attention to the direction the filament is wound. We want the filament to unload from the top. Lay your spool down so that it will unwind form the right (spool turns clockwise while unloading). Using a little hot glue, glue the sleeve into the center of the spool. Don't use to much glue, I use 4 little dots (top, bottom, left and right). Using too much will make it very hard to reuse it on the next spool. Also be careful not to get any glue on the inside of the sleeve, too much friction will keep the spring and grip shaft from moving when needed and will break the spring.

To make this easier we need to make a jig. Take the two 1" x 2" x 5" posts and cut a notch in the top center 3/8" wide and 1/2" deep, Just big enough for the rod to drop in but not move too much. Attach the posts to the plywood with a 13 1/2" gap.

Using the end of the rod we left alone (full threaded) screw on one of the 5/16" nuts first. Now screw on one of the 5/16" lock nut backwards. We want the nylon end of the nut on the inside. This is to keep more of the nut in the slot on the support.

hint... install the 5/16" lock nut forward until the rod go's past the nylon ring, this will "tap" the nylon, making it way easier to get on backwards.

Turn the 5/16" lock nut down the rod until you have 4.5mm of thread showing. Now take the 5/16" nut and back it up against the 5/16" lock nut. This is just extra insurance to keep the lock nut from ever moving or turning.

Slide one of the Bearings onto the rod from other end followed buy a spacer.

Slide the assembled spring/grip shaft into the spool. For the wider spools use the small support ring to keep the spool from drooping.

Turn the rod so that the flat side is facing up (just to make it easier) and carefully and slowly slid the rob into the Bearing side. Tune the spool so that the flat spot in the center of the spring is on top. keeping your finger over the hole (to keep the spring from moving outward) feed the rod thru about 1/2" or so. Using one of the Bearings, slide it onto the rod and use it to push the spool all the way to the end of the rod. leaving the Bearing you used to slid that spool on, slid the next spacer on and repeat the same posses. After your last spool keep that Bearing in place and then screw on the other 5/16" lock nut but Not too tight, this is just to keep the spools from walking up or down the rod. if you want you can screw on the last 5/16" nut just like the other end.

You should now have the following with the fully threaded end on the left, lock nut, nut, bearing, spacer, support (if needed), spool, bearing, spacer, support (if needed), spool, bearing, ext. you should end up with 1 bearing between each spool and one on each end. The spacers keep the spool from walking down the spring/grip sleeve.

Some spools have a deeper inset then others (see photo of "RED" spool). In this case use 2 Bearings to make sure that the spools do not touch each other.

With all your spools in place, hold the rod so it won't turn and make sure all your spools can turn freely without turning the spool next to it. (a slight shift is normal) If so first try backing up the last nut and Lock nut. If it still has movement try adding another bearing.

I recommend pouring in the Reusable Desiccant Beads first so not to dirty your filament.. Spreed it out so its somewhat level, no need to make it perfect. For the best results use the full 2lb'.

Take the assembled spools, making sure that the spring side of the spools is on the right (fittings facing you) drop the rod and spools into the box making sure that the lock nut on the left side seats fully down into the slot in the support. Feed your filament into the tubes until they stick out the other end about 1/2" to 3/4".

The re-wind distance is around 250mm-300mm witch is great for Bowden style printers like mine but If your using a direct drive I suggest pulling out about 200mm and letting it roll back up. Keeping too much tension on the springs all the time will shorten there life span and the movement from the other spools could cause it retract to far pulling the filament in out of reach.

Thank you and I hope this is as helpful for you as it is for me.