A D-I-Y CNC machine such as like this do have 2 variable Z axis, one is automatic then the other one is manually configured, that involves loosening the 2 allen bolts then (reposition) lifting up the spindle motor itself and lock again, you can cut any material on this type of CNC, anything softer than the carbide bit is doable, aluminum is just a breeze on this machine, on my experience I cut a whole block of aluminum 80mm thick and shape it according to the customer`s preference, but that involves programming a custom CAM because the bit I used is only 1/8 single flute carbide, it can get a job done precisely and perfectly just like any other professional CNC machine but it needs time, let`s say a professional CNC machine can achieve that job within just 30 minutes, but on a D-I-Y CNC machine it took me 3 hours, same on everything but on a different time span, aluminum 1-3mm no questions asked it gets the job done quickly, you can even print your own picture in half 3D in the aluminum material using only a carbide V-bit, medals on brass, gold, silver, aluminum, high carbon steel if you want hehe it can do the job. for as long as the hardness of the material does`nt exceed on the hardness of the bit you`re using then it`s OK, another question will be raised, on a high carbon steel can it cut like 1mm per pass? absolutely NO! on harder materials you need to program the CAM @ 0.1 or 0.05mm to make it work without worrying about the bit getting dull. cabide bits can cut/engrave harder materials for days without getting dull, for as long as there`s cooking oil in it you`re good to go hehe, im not really using a coolant (I cant afford it) I use whatever is in my reach.