Slim case for WHY2025 event badge

Description and goals

This is a slim case for the WHY2025 electronic event badge, that sits on the back exposing most of the sides, including the spacer, that then gets part of the overall look, especially if printed in a contrast color as pictured.

The goals of this design was to make something that was nice to hold in your hands, with rounded edges, that didn't cover or inset the expansion port or power button. Some of the add-ons that work with the expansion port, follow the outline of the carrier PCB very closely and for those to fit, the edge of the PCB needs to be exposed in the top, which this case does. Personally I also think it looks good with all the connectors flush with the case, making it easy to connect both USB-C cables and add-ons to the badge.

To help keep the front plate in place and prevent it from bowing a little, the case creeps up on both sides and grabs the front, securing it in the middle and letting the screws (4x M2x12mm) in the corners handle the top and bottom part. This helps make sure the keyboard buttons stick up above the face plate for a better feel when typing.

No need for support and SMA cover

The design is made to be printed standing up without any support, except for the one designed as part of the model where the SMA connector goes out.

If you haven't soldered on the SMA connector for the LoRa antenna, you can leave the support in place, covering the hole, but otherwise it's easily removed with a set of pliers or maybe even with your fingers as it's only hold in place with a few small bridges.

Tweaks needed to fit your specific badge

As all of the badges where manually modified with UV hardened epoxy to cover up the battery terminals, they are all a little different on the bottom end around the corners of the PCB. If your badge has epoxy to the edge of the PCB, this will be in the way for the case and the easiest I have found is to simply cut a little of the inside of the case with a scalpel or similar.

The walls are solid to this is fairly easy to cut, shaving off a little material. In some cases you might also need to shorten the corner piece where the screw mounts if there is a lot of epoxy on your badge. It is in theory also possible to remove the epoxy on the badge, but as it is there as a safety measurement, this is highly discouraged, as it's easy to scrape off too much and cause a short or similar.

Screws directly into plastic or brass inserts

I have made a few different variants, with one of the differences being how the screws connect with the 3D print. One version is with the M2 screws directly into a 1.75mm diameter hole, which works OK if you only put it together once or twice, but if you plan on taking it apart and assembling it multiple times, the threads that are cut in the plastic will wear out and then the version with brass inserts are better.

Assembly

To mount the case, first remove the 4 original screws, as this case will use the same holes, but use M2 screws instead of the original M2.5. This is so that the screws clear the carrier board PCB instead of trying to cut threads into the fiberglass. When loosening the original screws, be careful, but you will likely have to use a bit of force, as they are pretty tight.

If you haven't already and want to solder on the SMA connector, this is a good time.

Similarly, if you would like to add a microSD card, format it with the FAT filesystem and insert it into the compute module (you will probably need to remove the module from the carrier board to be able to insert the microSD card, as the battery holder is in the way).

If you want the lanyard mounted, it's way easier now, compared to after it has all been put together.

If you opted for the variant with brass inserts, place the 4 inserts into the holes with the end that is a little thinner first and then use a soldering iron or dedicated insert tool to heat them up and press them in. Don't use too much heat… maybe something like 170°C or similar and be careful that they go in straight. I usually press them in almost flush and then turn the case over and press it in the rest against a piece of metal or a flat work surface (remember that the insert is hot from the soldering iron).

Then stack up the carrier board, the 3D printed spacer, the keyboard and the faceplate and place the sandwich in the case, gently pressing the sides out and the PCB stack in until both sides grab the faceplate and holds it all in place. If the case isn't fully flush on the bottom, see above regarding tweaks for your specific badge.

When you are all happy and you have checked that everything sits correctly (eg. checking that all the keys in the keyboard protrude through the holes in the faceplate) you can insert the screws and tighten, but not too much, especially in the top as you risk squeezing the display. If you are screwing directly into the plastic, you also risk stripping the threads, but that is more likely if your screws are shorter than the recommended 12mm.

OpenSCAD and different variations

This has been designed in OpenSCAD and has a few different parameters defined for the customizer panel in there. If you download and open the file in OpenSCAD I recommend you disable "automatic reload and preview", and use a recent nightly build fo OpenSCAD with the new Manifold backend, as there are some performance improvements, which this design benefits from. Even with these improvements on a modern computer, it might take a few minutes to render this, but it seems to be quite good at caching the computations, so you don't need to wait all the time.

I have included a few STLs both with and without the sides, if you would like a super clean case, and only have minor bowing on the frontplate.