Bench-top or welded frame

[JAZZCNC]

Again can't be arsed to read all previous posts but I get the gist you want to aluminum but there are other areas of design that could be better worked on than building a base which could hold up blackpool tower without flexing.
Also, do you realize just how much heat will go into those joints so closely connected and how much distortion will occur from that heat.?

The frame needs to be strong but doesn't have to be massively built because the cutting forces are mostly lateral. If Was using cutting 250KG blocks of Aluminium then yes go big to stop defelction but doubt you will be.

The best thing you could do to give best cutting capability in hard materials is to build strong gantry and think about how can keep cutter deflection to a minimum.?
Cutter deflection comes from a mixture of Z-axis/spindle and Gantry vibration/deflection. Gantry deflection is easy dealt with by building strong. Z axis/Spindle is not so easy because this impacts on other areas of machine like travels, tool lengths, clearences etc.

If want high clearance for thicker material or long tools then Long z-axis required which deflects more.
Likewise if only cutting thin material then a lower clearance allowing shorter Z axis is possible, but still got to account for tool lengths, clamps etc.
One option is to lift material to the tool and keep Z extension to a minimum but this isn't practical if wanting to cut range of materials and soon gets pain in arse lifting and surfacing bed each time moved.

But with little out the box thinking, there is a better way which allows Minimum tool deflection of any machine setup while still having high clearance. In fact, can have very high clearence and still only have delection equal to tool stickout.?

This is done by Getting rid of the Z axis altogether and raise/lower the whole Y axis. This way the only deflection is from the tool stickout and any deflection in the gantry beam and supporting frame.
Build the support frame and Gantry beam strong enough and then the only deflection can come from tool it's self regardless of clearence and material thickness.
Because your lifting the Gantry beam which spindle runs along fixed to solid back plate you remove the Z axis from the equation altogether so then can have very high clearence and still have low deflection because there isn't a Z axis to deflect only the length of tool sticking out the spindle.