Looks great! but I'd remove the lower corner brackets, shift the spindle mount down (this way you can mount the assembly higher to the X-beam, decreasing rotational leverage) and add 2 holes to mount the spindle mount from the back as well

 

Hi, Looks good.
Two suggestions:
1. Have you looked at the Shapeoko HDZ from Carbide3D, as it for a similar sized machine with similar requirements.

2. Have you considered putting linear rails on z plate? Advantage is rails help stiffen Z plate, and spindle better supported at higher z height. Of course it has other knock on effects to design but seen this advocated else where.

Do please keep sharing your evolving design.

 

Sorry no that wasn't clear, I meant having the rails on the spindle side rather than gantry side. Most recently seen it on Ptiwee's LR/BS CNC Router thread ( though he is using a cbeam rather than a flat plate)

 

Well, just make sure your spindle mount is out of the way of the screws for your linear rail carriages. Then it's just Spindle mount (from the back) -> Linear rail carriages -> Spindle mount (from the front) -> Spindle -> Let 'm rip

 

Something to consider is shorten the ballscrew length. One of the issues with the HDZ is that by the time that the screw is bound (threaded all the way down) a bunch of the magic little balls have escaped from blocks.

So if you figure out where the stopping point is based on the rail length you can then move the bottom block up and decrease the ballscrew. (I need to make about a 15mm block / spacer to ensure that the HDZ dosnt go beyond the end of the rails)