This is a waterproof 3d printable container intended for use with geocaches, but could also be used for other purposes. It seals with o-rings and has several features to limit water ingress and keep the interior dry. Everything is customizable for making the optimal container for the application.
- All parameters are customizable, including container size, number of sealing o-rings, text labels, etc.
- Option to include multiple concentric seals for extra water resistance.
- The design automatically figures out which standard sizes of o-rings best fit to the chosen parameters and includes the part numbers (o-ring "dash number") on the inside bottom of the container.
- Optional exterior cap clips latch on to the container when closed and resist the cap backing off from vibration or weathering.
- Inside of cap includes a pocket with perforated cap for including desiccant such as silica gel. The pocket can be filled with whole silica gel packets in the larger sizes, or filled with the beads for the smaller sizes. Even if no liquid water leaks inside, humid air inside the container can condense if the temperature drops. Including a desiccant mitigates this.
- O-ring grooves include retaining clips and raised sections to form a better seal with the suboptimal surfaces FDM printing produces.
- No overhangs greater than 45 degrees, including the threads.
The container consists of two parts, and an optional third: The container body, the cap, and the cap for the desiccant pocket (if included).
The pre-made STLs each include all the parts needed. Using the customizer, individual parts can also be selected.
The customizer can be used to create containers with custom specs, but the pre-made STLs included here encompass a few common configurations. They are provided in 3 sizes (small, medium, large), with 1 or 2 o-rings, and with/without clips. If you're unsure which to choose, a good compromise is
2 o-rings provides a better seal, but makes the top of the container larger, and requires ordering an additional size of o-rings. Clips can help prevent the cap from backing off on its own, but can also be prone to snapping off in some circumstances, and can cause opening and closing to require more force.
Here's a list of included sizes, dimensions, and which o-rings are needed for them. For the 1 o-ring versions, only the smaller of the two o-rings is needed.
- Inner diameter: 25 mm
- Inner height: 30 mm
- O-ring numbers: #126 and #134
- McMaster part numbers: 2418T148 and 2418T153
- Inner diameter: 50 mm
- Inner height: 70 mm
- O-ring numbers: #141 and #149
- McMaster part numbers: 2418T16 and 9452K156
- Inner diameter: 75 mm
- Inner height: 100 mm
- O-ring numbers: #153 and #155
- McMaster part numbers: 9452K174 and 9452K176
Material and Postprocessing
I recommend using PETG for its durability, strength, and UV-resistance. ABS may also work, but may be difficult to print screw threads with due to warping.
After printing, the exterior surfaces should be sealed to prevent water ingress through the interior gaps of the object. One way to do this is using polyurethane spar coating. It may also be possible to do this with some form of heat treatment. Be careful not to add much unevenness to the o-ring grooves or it may interfere with the seal.
Sizes: The design automatically selects standard o-ring sizes that are available from many manufacturers. If rendering the design with OpenSCAD, the chosen sizes are printed to the console. I'm not sure how to view these when using the customizer, so the size numbers are also printed on the inside bottom of the container.
Durometer: I recommend using soft o-rings (for example, durometer 50A) for better sealing on the rough 3d printed surfaces.
Material: A range of o-ring materials should work, but Buna-N is generally a pretty good choice.
McMaster-Carr carries suitable o-rings that fit these specs under the category "Oil-Resistant Soft Buna-N O-Rings".
The sealing and functioning of this container can be improved by adding grease to a few spots:
- Greasing the o-ring grooves and o-rings themselves can help seal small gaps in the 3d-printed layers surrounding the seals. It can also help extend the lifetime of the o-rings.
- Adding a small amount of grease to the main screw threads can help them operate smoothly. There should be no need to grease the desiccant pocket threads since they are not frequently operated, and the grease may interfere with the desiccant.
- If using external clips, a small amount of grease can be added to the upper exterior surface of the container to decrease abrasion on the clips and help prevent them from snagging.