I had some previous experience with 3D modelling, mostly using 3DSMax, but modelling in AutoCAD turned out to be a lot of pain. It seem 3DS Max was (waaaayyy!) more intuitive when comes to viewport navigation, or working with edges/planes/vertices.
On the other side I was able to find many 3D models for autocad of aluminum extrusion profiles on the internet, among them extrusion 30x30x8mm which I’m going to use .)
After some time (I’m too ashamed how long it took to say it ,)) I managed to draw first few elements of the frame, and imported Y carriage bar holders from Nutz’s Prusa i3 rework.