Magnetic PTFE Dry Box Fittings

thingiverse

These fittings are used to provide an airtight path from a filament dry box to a printer. They are magnetic which allows easily swapping boxes or changing filament. This idea was borrowed from [Thing 4402034](https://www.thingiverse.com/thing:4402034) but the design is my own. The main difference is in the quantity of magnets and how the fittings mate. My design requires two magnets such that any two fittings will work with each other. On each fitting one magnet is recessed slightly while the other protrudes slightly. This positively locates the fittings so there is no risk of binding. ### BOM The quantity of each part will depend on your use case. The quantities here are for one PTFE tube from a dry box to a printer with o-rings sealing the dry box and each connection. You can choose to replace the o-ring parts with non-o-ring parts if you feel this level of sealing is overkill. #### Printed Parts - 1x Dry Box Dual Block - 1x Dry Box Dual Backing - 1x PTFE Block - 2x PTFE Block (O-Ring) - 2x Cap Block (O-Ring) #### Purchased Parts - 2x M3 8mm Bolts - 2x M3 Nuts - 6x 4.5x2mm O-Rings - 2x 3x1mm O-Rings - 3x [PC4-M10 PTFE Push Fittings](https://www.amazon.com/dp/B078SRBDS7) - 14x [1/4" x 1/8" N42 Neodymium Disc Magnets](https://www.kjmagnetics.com/proddetail.asp?prod=D42) ### Assembly #### Magnets Each fitting requires two magnets with opposing polarity. All fittings should have their magnets installed the same way. That is, all protruding magnets should have the same polarity; all recessed magnets should have the opposite polarity of those protruding. Magnets are pressed into their holes and should be snug so that they do not come out when separating two fittings. I typically press the fitting down on a table in order to fully seat the protruding magnet. An M3 nut or another magnet can be placed on top of the recessed magnet when pushing down to fully seat it. These fittings are intended to work with K&J Magnetics' D52 magnets. There is some very small variance in the outer diameter of the magnets. If you find that a magnet does not stay in the fitting you may be able to swap it for another one. However I find this is rarely necessary if your printer is consistent. #### O-Rings The 4.5x2mm o-rings are used to seal the fittings. The fittings which have a recess of this size around the filament hole should have an o-ring pressed in. The o-ring will protrude slightly. This allows a positive seal against the opposite fitting. #### PTFE Fittings The PC4-M10 fittings should be snug but do not overtighten them. Doing so may damage the printed plastic part. The length of PTFE tube from the box to the printer should have one PTFE fitting with an o-ring and one without. The PTFE on the printer should have an o-ring. This allows each connection between the dry box and #### Dry Box Fittings The dry box fittings are designed specifically to work with [Thing 4493689](https://www.thingiverse.com/thing:4493689). The filament holes are spaced at 80mm and will likely work well with other DIY dry boxes. These fittings use 4.5x2mm o-rings to seal the filament holes and 3x1mm o-rings to seal the M3 bolts used to attach them to the box. All four o-rings are installed on the outside block. Insert the bolts through the outside block and then place the 3x1mm o-rings onto the bolts. The two nuts sit inside the hex shaped holes in the inside block. You will need to drill holes in the box for the bolts and filament to pass through. Once done you can install the fittings and tighten the bolts so that the front block sits flush against the outside of the box.