clockspring3D

Raspberry Doughnut Pi Case! (4B, 3B, 3A)

Added 2022-01-24 14:43:22 +0000 UTC

Yes, it's a Raspberry Pi doughnut case with sprinkles!

This one took a while to come together. You'll no doubt remember mid-last year we had some delicious printed doughnuts. Well, at the same time as putting those together I started on a Pi case based on the same form.

However, there were plenty of questions to be answered, like how to expose ports, how to allow for cooling fans, how to handle multiple types of Pi boards, and most importantly, what to do with the big hole at the top! So, I'd poke and prod, try a few things, then put the design aside for a while until the pile of test-printed doughnuts glared at me long enough to draw me back in. Let's look at how it ended up...

Assembly

Here's a render, because it's really hard to hold printed parts in mid-air...

We have a main body with a separate cover for the cable port (more on that below), a grille that sits on top of the Pi and which can hold a 30mm fan, and then the icing itself!

Attaching the Icing to the Doughnut

The best way to attach the two main parts together is to use M3 bolts! Any size between 12mm and 16mm will work just fine - longer than that and you'll hit the end of the bolt hole and possibly poke out through the icing.

There are alternatives, though. The bolt holes also have room for 6x3mm cylindrical magnets as another options. Is this a good idea? Could there be an impact on some aspect of performance or operation? I'm really not sure, and I couldn't find anything definitive on the matter. At any rate, this isn't a case you'll be opening and closing often, so bolts are a better idea, really.

If you really wanted to you could always just stick some double-sided tape between the parts, but really, M3 bolts are a much better plan.

Cable Port Covers and Cable Routing

We have a few options here!

Those cable panel covers slide in from the top along two guide tracks, and are held in place by the icing. Depending on how many ports you're planning to use, you might choose to use the minimalist grille or the wide-open version. There's an allowance for cables from the side of the board to be routed past the edge of the

You could also just use the fully enclosed version that has no cable holes. Why would you do that? Well, you'll notice that the grille design around the entire main body can actually be trimmed with cutters if you so desire. So, if you wanted to, you could just route the power cable straight out the side (this could be useful if you particularly want to use a cable that doesn't fit nicely - I have some that do, and some that don't!

Similarly, the interior bolt post that sits in front of one of the ports is intentionally not strengthened like the other three with side buttresses. It can be broken off or cut out to allow for cable routing if necessary.

Fan Grille (and Non-Fan Grille)

The fan grille serves to close the hole in the middle of the doughnut in a nicely decorative way, but it also (optionally) holds a 30mm fan to cool the board. There are two versions of the model - one with the fan bracket, one without.

The grille frame sits on top of the board and locates against other features of the main body. The GPIO pins are left exposed so that the fan can be powered from there!

Supported Boards - 4B, 3B, 3A

The benefit of the swappable cable covers mean that the case doesn't need to be specific to the layout of particular boards! I've tested it with Pi 4B, 3A, and 3B.

Mounting Strip and Desk Stand

Just in case you want to proudly display your Raspberry Doughnut Pi, there's a nifty desk stand! There's also a mounting strip, mainly to make it easier to mount onto extrusion.

Both of those use a two-sided keyhole shaped hole in the doughnut body. Be nice to the little prongs on the stand and the mounting strip, though, they're quite small, and while they're reinforced it would still be easy to break them off! The case body will be fine, though.

Printing Tips

None of this is particularly tricky! All the angles are nice and friendly, and no supports are required. You might want to use some thinner layers on the icing and/or the sprinkles to better render the smooth curves, but that's purely an aesthetic thing. The sprinkles might also be easier to print on a raft, being so small!

In terms of print orientation...

* Main case body prints right-way-up.

* Icing prints right-way-up

* Cable panels print either right-way-up or back-down depending on the specific panel

* Desk stand sprints right-way-up

* Sprinkles print right-way-up.

* Mounting strip prints flat-side-down.

* Grille frames print with the grille down.

Print Dimensions

The main body occupies 127mm x 130mm on the bed, and is 34mm tall. The other parts are smaller!

File location

You'll find this one on Dropbox at 695 Raspberry Doughnut Pi