450x300 Aluminium extrusion build from scrap/used parts

[Clive S]

I'll be using 80x40mm extrusion that I may be able to get my hands on for free. If not, I'll weld the frame from 50x50x3 steel box section.

If you can get 90x45 extrusion you will find that the spacing holes on the BK12 and BF12 bearing blocks will line up with the slots in the extrusion

[Neale]

Even if you use 1-1 belt drive, it can let you tuck the motors almost entirely within the machine envelope - reduce space and remove vulnerable sticky-out bits. There is also a feeling that it can reduce resonance effects although I have no experience of this myself. I went belt drive for space reduction, plus thought that it would allow me to change stepper-ballscrew ratio if needed. I found that this was one design decision I did get right, though, and I have stayed with 1-1. Works well for me (similar size machine).