Fixed Gantry Design - Input Appreciated.

[Electroconducive]

So, After spending a lot of time working through quite a few designs, many hours in CAD and reading lots of build logs. I have settled on a fixed gantry style design. I only need 500x500mm of working area and quite a high Z of 250mm. The machine is being built to mill aluminium, copper and plastics. So, strength is more important to me than size. I intend to use it mostly for electronics enclosures and PC watercooling blocks. Given I have no current machining capability, I have been designing with that limitation in mind(epoxy level all the things).

I have settled on two Z designs. The standard 25mm alu tooling plate design and the novel steel gantry.








The frame measures 1000x800mm. It is made of 100x100x4mm welded box section, with the gantry bolted to the base via two 10mm thick steel plates. The steel Z is 60x60x5mm box section. All alu is 25mm thick tooling plate.

I am wondering, which Z design would be the best for my application?

The overhang of spindle from the main gantry is 35mm more in the steel design than the aluminium. However, I would just like to go with the best option given my current capabilities. I am not competent enough to do a thorough FEA analysis of the options. Besides, I thought I'd ask those with the real world experience.

What do you guys think?