Hey Jazz,

No worries about throwing a spanner - I really appreciate the advice!

1. Diagonal bracing makes perfect sense. Do you think triangular plates or more box section at a 45 degree angle would be better?

2. Ball screw alignment on X. I was planning to make oversized holes in the box section to allow for radial adjustment (ie. not threading into the steel but using a nut on the inside of the box section). I was thinking I'd put the gantry at one end, fix the bearing in place then move the gantry to the other end to fix that one. Do you think that would work? Do you also need adjustment in the axial direction somehow? I've actually got double fixed bearings for both X and Y (FK for X, BK for y) as I read somewhere that was better.

3. Ball screw alignment on Y. Here I was imagining I'd fix the double BK units to the 60x30 extrusion in the middle of the two 90x45s, then use oversize holes on the rails to do the same kind of thing as above, only this time allowing the rails to move slightly to make sure there's no binding. Does that make sense do you think?

4. Z axis rear plate. I'll scrap that in favour of some plates at the sides as you suggest.

5. Y axis belt protection / gantry style. Yeah, haha, funnily enough I'd had it the 'other' way around in all my designs up until the last revision. I changed after reading the thread where someone made a diagram showing the 'screw behind' approach wasn't as good. I get what you're saying though - it was definitely cleaner the other way around and kept everything out of the way. I'm kinda thinking I might switch it back.

6. Rear belt. I think I'll just put a board at the back to keep the chips away from this - seems easier than re-routing the belt.

Thanks again for your thoughts :-)

Cheers, Simon