Update 4

The last few days, I was designing the case and fixing bugs and problems on my PCB.
First, I laid out all the components I need to minimise the space and wiring. I came up with the idea that I could use the power supply (the silver shiny metal box) as the base and put the stepper drivers (the black boxes with the green connectors, TB6600s) on top, facing upwards with the connectors on top. This way they are compact and easy to wire. I only had to find a way to attach them to something underneath, so I designed a layer between the top of the power supply and the feet of the drivers. The Raspberry Pi (the red and white box) is almost the same size as one driver, so I can put it at the front of the line of drivers. The same goes for the PCB I designed. I also had to keep in mind that the USB cable needs space and that the Raspberry Pi 5 is powered via USB-C on the top.
While planning the box, I noticed that I also have to cool the drivers. Luckily, I found some old PC fans in my storage with almost the perfect dimensions: 80 × 80 × 20 mm. They were really practical because I had some space left on the left side of the drivers, and one fan can provide airflow for three of the six drivers. So I was really lucky that I already had two of them. The only problem I will have with them is connecting them. One fan only has two wires, 12 V and GND. That’s not really a problem; I just have to add another voltage level to the box. The other fan has four wires, which is a bit more complex. I haven’t done the research on that yet, but I will hopefully figure it out. I know that two of the wires are 12 V and GND, and the other two are for PWM/control and RPM feedback. I still had some GPIOs left on my PCB, so I also added connectors for them, which could be really helpful for controlling the fans. I’m not sure yet if or how I can use them, though.
If you know anything about this or have some ideas, I would be happy to get some comments, so please write something if you want!
After figuring out the layout, I opened Fusion 360. I was also thinking about which material I should use for the case. 3D printing would be easy, but at this size it would take a long time, use a lot of filament, and my 3D printer is too small anyway. So what other options do I have?
Metal would also be a good material, but I can’t weld or bend it, and CNC machining metal would be expensive and heavy for something that doesn’t really need to be made out of metal. So there was one final option:
WOOD.
My father has some plywood lying around, so it would basically cost me nothing and is relatively easy to work with. Unfortunately, I’m sometimes a perfectionist when my German side kicks in, and I’m also not the best at woodworking. But I can do CAD. So I came up with the idea that wood could actually work if I can find somebody with a CNC machine to cut it.
Disclaimer: I haven’t asked anybody yet, but next Tuesday I’m going to ask around at the local workshop to see if I can use a CNC machine there. Otherwise, I might have to wait until the end of the holidays in three weeks and ask my teacher. But like I said, I already designed the whole box.
I used the layout I figured out, the dimensions of all the components, and a wall thickness of 9 mm, based on the plywood I have available. Instead of just putting everything into a simple rectangular box, I designed the inside around the components themselves. This should keep everything in place and hopefully make the wiring cleaner. I also added ventilation slots to the case so the air from the fans has a way to move through the enclosure instead of just blowing against the drivers. I also already added all the holes at their hopefully perfect positions.
I will use M3 and M4 screws, as well as some wood screws that I will hopefully find somewhere in the box in the garage.