Oh crumbs. Here we go!

[Jonathan]

From the picture, unless it's a twin start screw, it looks like you got RM1605 for the longest screw, not RM1610. Assuming the ballscrew is 1150mm long, as per the original post, this will limit you to about 8.5m/min due to the critical speed. That speed is plenty, but I doubt you will get it with 3Nm motors unless you have a 2:1 ratio between the motor and the ballscrew to get 10mm 'effective pitch'.

20mm is plenty thick enough as a back plate for the Y-axis, so long as you have some box section or extrusion bolted to it to increase the strength parallel to X and the torsional stiffness. It will be much more rigid if you have the ballscrew directly between the rails, so on the same side is good.

[hoppo]

Hi Jonathan, thanks for your post. It is indeed a single start RM1605 and 1150mm in length. I was planning on trying to drive it directly with a Nema 23 3Nm stepper but after your post I'll now somehow implement using pulleys to drive the x axis. So much yet to learn, but hey that's half the fun! On the subject of ratios will the RM1605's be ok for the shorter Y and Z axis's being driven directly? I saw a post on here that recommended this site Bearing Station - Adhesives, Bearings, Belts, Chains, O Rings, Oil Seals, Pulleys & Sprockets so I'll start to have a look at what would work, unless you've got any other recommendations. I was also beginning to think of using two screws, instead of one along the x axis. Would this make a difference or if I did go down this route would you still advise on using a 2:1 ratio but on both screws?

I've decided to definitely use aluminium plate for the Y axis, it just looks and feels more solid, and the prices are comparable, having looked on aluminium warehouse. Would I need to use ecocast for the backplate or would 6082 do the job? I'll probably be looking for someone to machine the sides for me, and then I'll drill it tap it and bolt it together. Anyhow I've attached my idea for the Y axis. As usual any comments appreciated. And also as usual many thanks for all the help so far. I'm sure there'll be loads more questions.