Introduction: Weatherproof Laser-cut Arduino Enclosure
Here we document how we built our own custom weatherproof* Arduino enclosure by laser-cutting acrylic and rubber.
* Weatherproof does not mean waterproof. This enclosure is not safe for immersion in water! Nevertheless, 5 out of 6 sides of our enclosure are waterproof, while the last side is only weatherproof. The enclosure is meant for environments where no water would enter from below.
- As small as possible to fit our space constraints
- Be weatherproof in case of rainfall
- Transparent to see debug-LEDs
- Exit of 5 cables (Power, Ethernet, 3x sensor cables)
- Easy to open and attach/reattach cables
Here is a closer look at what our Arduino components look like.
There are many waterproof enclosures out there (see here or there). The tricky part is to prep them for your cables to enter/exit the enclosure. The professional approach would be to insert cable glands with tightening silicon grips into the panels of the enclosure (see here or there). But they are bulky and require you to solder or wire connectors after the cables had already been inserted into the glands. It would be hard to extract the cable again without a resoldering or rewiring job.
Our design here shows an approach for a more temporary solution that allows to easily get into the enclosure to change and plug/unplug cables.
Step 1: Parts Needed
- transparent acrylic sheet (here: 3/16”)
- natural rubber (ordered from here)
- cardboard for prototyping (ideally similar thickness to final acrylic)
- acrylic cement (TAP)
Step 2: Basic Design
First, measure the exact dimensions of your electronic components. That'll give you the inner dimension of your rectangular enclosure. In our case the enclosure was designed as tight as possible, to not allow for any movement of the Arduino inside the housing. We'd recommend you now tape together a first prototype box made from thick cardboard. Holding a box in hands always makes it easier to think about how to further design it's functionality.
How to open the enclosure
The first problem to solve: How are you going to open your enclosure? Instead of giving the enclosure a lid, like shown in the image above, we opted to only leave an opening on the shorter side. It allows to slide the Arduino in from that side, and leaves all the other panels and edges to be permanently closed and therefore waterproof.
The locking gate
To block the open side of the enclosure that has all the cables exiting, we designed a “locking” gate that can be slit into the enclosure from the outside, and forms a locking wall with a narrow pathway in the middle for the cables. (To weatherproof the opening that still exists we'll add a rubber layer with exact cutouts later in Step 7!)
Step 3: Vector File
Design box joints with vector software
After the basic design is done, it is time to make the exact drawings with a vector software (free+opensource:inkscape). To join the enclosure walls to each other, we went with a basic box joint / finger joint method, where you cut your walls with square puzzle-edges that fit together perfectly. If you plan on having flush enclosure edges, you’ll need to know the exact depth of your acrylic sheet beforehand, to know how deep to draw the joints. For our enclosure we went with transparent 3/16 inch acrylic - mainly because it provided more glueing area than 1/8 inch acrylic and felt less bulky than 1/4 inch acrylic.
Don't forget to add flanges with screw holes, so you can mount the enclosure to a stable structure.
By the way: there are software options - like BoxMaker - out there that allow you to generate box joints easily. For more flexibility and custom needs though, you’ll be better off drawing your own design.
Once your design is done, it definitely doesn’t hurt to print out a paper version of your enclosure design, just to make sure you put all your finger joints in the right location.
Something we learned later in the process but should be mentioned here: Contrary to other CNC machines, laser-cutters cut exactly on the line which means that obviously the width of the laser beam will cut away some of your material - called the “laser kerf”. If you want to end up with tight finger joints, you will have to make your tabs slightly bigger and your slots slightly smaller in the vector design (see here). We ended up finetuning the exact fitting in a couple of iterative rounds of laser-tests and assemble-tests.
If you managed to reach the perfectly tight-sitting joints, be aware: Using the same design later again, possibly with a different laser-cutter (same model though) or a different laser-focus setting, won’t guarantee you’ll get the same results.
Step 4: Lasercut Acrylic
Find your lasercutter of choice (or availability) and get down to cutting the acrylic. (This instructable won't tell you how to though.)
Make sure to cut only two pieces first, so you can test the tightness of your joints before going into mass production. As mentioned before, the age, quality and focus of the laser can affect how exact your cuts are.
Dry assembly time
Once your are done cutting, peel off the protective plastic film off your lasercut parts. And now to the fun part: align the notches and snap your box together! If the notches are tight, the box will hold together by itself. Which is a good thing for the next step of gluing, because then you won’t need an extra hand or some clamps to hold it all steady.
Step 5: Glue Acrylic
Acrylic can be glued together with acrylic cement, which is a solvent that actually melts and chemically bonds acrylic surfaces to each other - hence name "chemical welding"! We used TAP Acrylic Cement. For applying it you’ll need an appropriate applicator (bottle or syringe), some disposable latex gloves and safety goggles.
Glue along edges
Take your already assembled acrylic box and apply the glue along all the edges and notches. Even if your notches are tight, you will still see the glue spread in between them. It's better to apply more glue than less.
Once you've glued all the edges of the box, hold it tight for a little while, trying to apply pressure to all glued joints at once. The bonding should be already very strong after 10-15 seconds. After that you could put some extra weight on the box, while it sits for a bit. After 24 hours the bonds should be as-good-as-it-gets.
The transparent acrylic makes it at the same time easy and hard to monitor the spreading of the glue between the surfaces. You’ll need good lighting to see the fluid and little bubbles that appear between the acrylic layers. We even missed some non-alignments of notches, because it was so hard to see those transparent edges!
Double-glue the top panel
The mountable flanges on our box are on the top of our enclosure and therefore the surface most likely to be hit by rain. To make sure all the glued edges of the top panel are really solid, apply an extra layer of acrylic cement to it: After the first round of glueing and drying, drop a little pool of acrylic cement into one of the corners of the enclosure. Then slowly swivel the box around for the extra glue to reach and cover all the inner edges.
Waterproofness over prettiness
If you are - like us - more concerned with the waterproofness than the prettiness and cleanliness of your box, you should definitely use more glue than necessary. The extra glue that spills out will evaporate quickly. It’ll leave some smears on the surface, but at least you can be sure that no water-drop will be able to enter through those edges.
In case you discover after glueing that there is an actual visible gap between some of your joints - for whatever reason - the thin water-like acrylic cement won’t help with filling that. You will need a glue that’s a bit more substantial, a bit more gooey, like SCIGRIP Weld-On 16 Cement.
All that glueing does slightly add material and/or deform your acrylic. We discovered after glueing that the opening gaps for our locking gate were now slightly too tight, and therefore had to recut some of our gate pieces.
Step 6: Water Test
To test your gluing skills, you can do an actual water test. Fill your enclosure with water and watch for leaks. We definitely found some, and then had to go back and put some extra glue on some notches. Nobody's perfect!
Step 7: Lasercut Rubber
Rubber for extra weather protection
If mounted in the right orientation the cable-entry of our box will always be at the bottom-side of the enclosure. So, unless there’s water coming from below, the opening should be rather safe from water entering. Additionally, the opening on that bottom-side has some extra protection from the slightly overhanging side panels. But, to be safe, we decided to add an additional protective layer.
To completely keep water out of something, you need a material like rubber that is flexible and squeezes super tightly against your components. All professional waterproof enclosures have silicon fittings or silicon layers along the edges of openings.
Natural Gum Rubber
We opted for some Natural Gum Rubber (40A Durometer, link). When cutting elastomeres on laser cutters you are pretty safe when choosing Natural Rubber. Still, double check your laser cutter is up for the task.
Design with Vector Software
- Measuring cable diameters and cable positions
- Start the vector file with a rectangle with the inside dimension of your enclosure
- Place circles (or ellipses) for your cables
- Connect circles to the edge with simple straight cutting lines (=“access lines” to slide your cables into place)
Getting it right
To get a rubber piece that sits nicely with all the cables, you will most likely have to do a bunch of test cuts. If the opening for the cable is too big, it’ll leave a gap, if the opening is too tight, then the rubber flaps will push apart and leave a bigger gap along the access line. Also, make sure your cable holes are exactly placed, because the rubber is not structural. Your cables will push against it and deform it, if the holes are not exactly where the natural resting point of the cables is.
Alternating access lines
As you notice, we ended up having the access lines alternately coming from different sides. That’s because our cables are sitting very close to each other and too many cutting lines next to each other would make rubber sheet rather unstable. By alternating the lines - one up, one down - both sides of the rubber piece were evenly stable.
A note about natural rubber:
We ordered two sheets of the same Natural Gum Rubber product and even though those sheets had the exact same specs on them, they behaved slightly different. While one of them went all sticky and smelly by laser-cutting, the other behaved rather well. There was also a slight difference in their color (you can see that in the image with the six rubber pieces). In the end, both rubbers worked out, we just had to clean one more than the other
Step 8: Finished Assembly
Final assembly steps
- Squeeze the rubber onto the cables of your electronic component.
- Slide the whole thing into the enclosure.
- Close the box with the locking gate.
- Make sure the rubber layer sits nicely against the locking gate, as straight and flush as possible.
And that's it!
What else is there to say
You might say, there is nothing in there that actually holds the Arduino in place inside the box. This is correct, but because our enclosure was designed super tight, the Arduino almost holds itself in place. Besides. it can’t fall out the bottom, because the cables are blocked by the locking gate. And the rubber layer provides some additional friction to keep everything from sliding around.
This project was done while working on Knock Stop Music, a installation created by Daily tous les jours and commissioned by Autodesk’s Pier 9 under their Creative Projects umbrellas. We also wrote these other instructables as part of our work there: Add a Bending Computer to an Analog 3-in-1 Sheet Metal Machine and Everything You Always Wanted to Know About Cardboard
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