routercnc,

Looks good John. Some thoughts are:
You could centralise the end plates on the horizontal plates so they are directly above the X bearing carriages and bolt from underneath and not include the angle supports. The bolts into the X bearing carriages may just about straddle this end plate but if the bolt access holes to the bearing carriages underneath is obscured then add a second horizontal plate to bolt to the carriages and then bolt these to each other.

Yes, I could use two 12mm horizontal plates instead of the one 25mm one. That might make for easier alignment. Could mill an alignment rabbet on the bottom of the carriage plate to square the two carriages to each other.

One end plate could be extended rearward slightly to accommodate the stepper which then belt drives to the ballscrew.

Ok. Was going to direct drive everything but belts and sprockets might let me move a little faster with the 5mm ball screw pitch. What are the pros and cons of direct drive vs belt?

Make sure the extrusions and joined to each other to get the section benefits.

I have ideas for both internal and external fastening methods. Will try them and see what works better.

Check how you are going to drive the gantry and connect the X ballscrew nut before finalising the exact layout otherwise you might need complicated joining brackets either on the gantry ends or the bed ends where the stepper and bearing blocks are fixed.

Yes this was just a layout, not enough detail yet for a design. Looks like it might be time to put in the details.

Thanks,

John C