The advantage of aluminium shapes is that it’s easy to use and to integrate. You have a very strong structure with a reasonable weight.
I started by fixing the linear guides and the ball bearings on the lower structure :
Then I fixed the Y gantry :
And finally the Z axis :
For the driving screws I used normal screws that you can find in any DIY shop. I chose them because they are cheap, and they have a low pitch (advance in mm per rotation) . Here I have 1.5mm per rotation, which leads to a better precision, but it is also easier to find or make a driving nut. For the nuts I used a block of PEHD I made myself an then threaded with a standard tap. For blocking the driving screws I used Nylon Hex Locknuts which are pushed against a nylon washer. This system is easy to integrate and I didn’t had any problem with this solution.
After fixing the cables carriers, here is the final result :