Fixed z axis to gantry design

[JAZZCNC]

I agree with Rob completely increase the size and stay with this design or switch design completely.

Personally I'd stick with this design and increase size because it's a very strong design and ideal for cutting alumnium.
If you do need moving gantry and switch design then stay away from high gantry sides and go with frame that has high sides with rails on top and Gantry sat directly on bearings. It's the only design to use of your wanting to cut aluminium.

Also I'd re-think those SBR rails if your cutting Aluminium has you WILL REGRET it down the line.!! It's alot of work and money to spoil with cheap rails that WILL show there weakness in the finish and accurecy you achive.!