Design Help Pt2 Required for CNC design/Build

[JAZZCNC]

I can make a few suggestions that you might consider having built a few machines very similiar for the same job and actually have one part built which I just don't seem to find time to finish.! I'll attach pics of it.

Looking at the drawings I presume you intended using twin screws.? If so then I would put a cross brace between the gantrys sides running under the bed, this will help make the gantry more ridged but it also then gives you the possibilty to run the ballscrews under the bed out off harmsway rather than exposed on the outside it also offers some protection from dust and rubbish.
On the machine I build the motors under there as well connected to the screws with belts. Other than the protection advantage the belts also allow geariing if needed and reduce the chance of resonance, but the main reason in my design was to keep the foot print as small as possible because the original machine was to live in a typical 8 x4 garden shed/workshop so space was precious. As you will see from the pics the Y axis motor/screw setup was inverted the same and the Z axis motor flipped to keep the height down so it could sit on a bench without hitting the roof, there are no components sticking out side the initial footprint.
I've built several versions both with single screws and twin screws, some with belts as mentioned, some with direct drive and motors on outside when space saving doesn't matter as it does ease the build cost slighlty slightly. Thats why some pics will look differant to others.

Regards the largish kink'd back gantry side, thou not a problem as such it's more material related.! . . Depending on the material width you intend to use you may want to check that you can actually get that much kink out the width's.? Unless you intend to use one large and expensive sheet then it could be tight using STD width's from the likes of Alu warehouse etc.? Most stop at 300mm width.!

Regards the Z axis I would run the rails on the Front plate and put the bearings on the backplate, this will help strengthen the front plate slightly. I would also recommend you at least beef up the Z axis with min 19mm plate. Remember it doesn't matter how well the rest of the machine is built if the Z axis flexs then accurecy goes out the window.!

Hope this helps and happy building.