Advice needed for Z Design

[Hobgoblin]

Priceless information!

I had planned to have those brackets like that for holding the ball screw suport block bearings but i suppose they could be tapered towards the middle, but i think ill be going away and having another go at all this tomororw now.

I am unsure as well on the size of the hiwin to use, type of profile and bearing block.

Planning to use 20 plate here, and bracings similar to that on the x axis gantry base.

5 mm pitch check, but what about the diameter 16 or 20?

Thanks

[JAZZCNC]

16mm dia screw will be fine.

The rails I'd use 20mm.? Not that 15mm won't handle the loads they easily will BUT the bearing sizes are tiny and the small size creates issues with clearances for the ball-screw. With 15mm you end up having to put stand-off blocks between the plate and rails/bearings to create the clearance for the ball-screw and Ball-nut.
Even with larger and taller 20mm you still have to create some clearance for the nut, usually by machining a shallow channel in F & R plates but it's much nicer and neater way IMO. The longer 20mm bearings also provide a bit more support has well.