Starting to design out my build, looking for critique

[AndyUK]

I'm still aware I haven't gone through your calcs yet... Finding time is hard! Sounds like with the design changes though I may wait a little longer :)

I second Washout's comments about the CS labs stuff, looks brilliant. The thing that put me off was that the base model is only 4-axis, and it doesn't handle slave axis homing native-ly (although there are decent workarounds posted on here). Anything more than the base model is horrendously expensive, and I wanted future expand-ability to add a 4th axis which is gone if you use the 4th for a slave - but you avoid both of those issues by having a connecting belt and single motor.

Also, on the four rails idea, I think you'll definitely end up spending a few days becoming best mates with your dial gauge - but it could pay off in the end?

First impressions on the redesign; I think your CAD is coming along nicely, really shows. I do have a few concerns though:

• I question the Z axis travel length and why the plate is so large - Don't forget you'll have a bit attached to the end of your spindle, and its going to have to be quite a long bit to make use of your Z travel. I've got 18cm, and honestly, its probably far too much, most of the time you're really only needing to cut say 18mm plywood! The distance between the bed and the gantry looks huge - All that Z extension reduces the rigidity of the machine. Have a think about what you really need - can it be acomplished in other ways, such as an adjustable height bed or overhang section which keeps everything stiff for the majority of the time, but when you need to use the router on something large you can?
• How are you going to assemble the Z axis? Look through the design, building it up step by step, and imaging when you will or won't have access to each screw and what that implies. I've got my ballscrew and motor on the fixed bit because I can easily get to the four screws holding the ballnut onto the Z plate, undo them, then slide off the rails. Your design looks a little harder to physically assemble.
• The C beam - how are you going to attach those profiles to each other? Any weakness here will be quite problematic and you've got two joints which need to be constrained.
• 10mm of steel looks quite beefy for a side plate, but 3mm seems quite weak in my head. I realise its intentional, I'm just not convinced!