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.

PCB Design

I designed the PCB, trying to keep all components as compact and close together as possible. I had some difficulties deciding on the layout, especially because of the position of the USB port, where a cable will need to be connected later. I also had to consider the appropriate trace widths for the different signals and power connections. Later, I added M3 mounting holes to make it possible to securely mount the PCB.

I wrote down the plan based on all the thoughts and little sketches that were scattered around my desk.

Explanation:
The robot arm has six stepper motors for its six degrees of freedom (DOF). These motors require drivers, so I will use six TB6600 stepper motor drivers. I chose them because they are reliable, can handle the voltage and current required by my stepper motors, and I already had bought six of them for this project.
I also tested TMC2209 drivers from BigTreeTech, but I could not get them to work reliably with my Arduino and the stepper motors I bought. During testing, I also fried several of the drivers.
The stepper drivers are controlled by a motion controller based on a Raspberry Pi Pico. It calculates the required steps and speeds based on commands received from the RP5 via USB and sends the corresponding STEP/DIR signals to the drivers.
The Raspberry Pi Pico is powered through a DC-DC buck converter. I chose this setup because I am concerned about potentially damaging the RP5.
The Pico is also connected to seven limit switches, which are used to home the robot arm. I have seven switches because I had one pin spare, which I plan to use for another function later. In addition, the controller has an enable-control LED and three servo outputs, which I will need for additional functions and could connect because I still had three GPIO pins available.
The six stepper drivers are powered by a 500 W, 24 V, 21 A power supply.

I was drawing circuit diagram from part research and sketches assigning the footprints. Sadly I wasn’t Recording my self doing all the research, I was making a plan searching for parts testet some things, but thes like 5 h don’t count now what is realy sad. Now I will make the sketches go online and I explain more the plan befor i proceed with desining the PCB.