Need advice on gantry design

[jcarpenter]

First real post! Looking for advice on moving gantry design.

Proposed machine cutting area: 1220mm x 1220mm cutting area (1/2 plywood sheet)
Materials to be cut: Foam, Hardwood, Plywood, Aluminum to 6mm thick.

Proposed machine parameters:
Floor standing
Moving gantry with high wall frame
Gantry beam length about 1500mm
Twin X axis ballscrews, single Y and Z
Non-production environment
Need decent but not perfect finish on edges of aluminum plate.
Would like to hold plus minus 0.1mm on dimensions

Materials available for the router build:
80/20 extrusion 3030 (76mm x 76mm)
80/20 extrusion 1530 (38mm x 76mm)
6mm aluminum plate
15mm plate
20mm plate

Shop tools available:
20 inch bandsaw
Full size CNC knee mill
Small CNC lathe
300mm x 300mm CNC router
Small shear, small pan break, air compressor, die filer, etc.

Experience:
Amateur CNC machinist. Built a couple of small CNC routers and some custom automated machinery for pool cue
builders. Just enough knowledge to be really dangerous.


First picture is what my design looked like before searching around this forum for a while. Looks like I hit all the usual problems
such as:
Separated twin beam gantry
Ballscrew between gantry beams
Thin Z axis plate
Z axis rails not on Z axis plate
Single gusset plate to hold end extrusions to gantry carriage plate

Probably a lot more problems lurking in that design. So I am starting over. And the first thing I want to do is to settle what the cross section of the
gantry should look like using the materials available to me. The second picture is of some gantry and Z axis plate cross
section views with different configurations of extrusions. Trying to come up with some ideas that combine the recommended
box or L box beam construction with things I have on hand.

Do the drawings make sense? Any of my ideas decent? Got any suggestions?

Thanks,

John C