Going out on limb and thinking you have very, and I mean very little experience in metal work.
First, I personally wouldn't do work in Al unless it had material properties for it. Al is unforgiving, relatively expensive to play with, does not play well with other metals, and is just icky. I am not a machinist - I know some machinist love it. One of the nice? things is you can cut it with a jig saw, coping saw, skill saw, jewelers saw (with right blade), a bench top band saw, table saw.....
so, flat part, no experience, easy to get, ok al is good call. a file will make short order of any wobble edges - a little practice and those will be minimal.
You mentioned engraving. No way unless you are really good would you touch al. Engraving is metal removal, with a tool, a true craft. lasers more etch the surface, big difference. There are cnc and pantograph engraving machines, yet you can get better quality with a hammer and engraving chisel - touch up with a push graver. Look at a dollar bill or a fancy shotgun for examples. Steel and navel brass are the common materials to learn and practice on.
Now, you are being secretive so I assume bending or breaking. Al alloy matters for bending, and there are various definitions of 'merchant grade' - steel you have a36 (mild steel). Stainless merchant is 300 series - you do not want to start breaking you teeth in on stainless.
Try roofing copper, can cut with aircraft shears, sands and files readily, you can form it easily, forgiving as can be, you can anneal and keep going with a benzomatic torch or kitchen stove and a mudpuddle, you can phoscopper, lead solder, or even use silver solders for high strength joints (not the 15 % silver, the hard - medium - ez - extra ez stuff). you can engrave it if half hard or better, you can enamel on it for finish once you mastered everything else.
Second your title is vague
Third step quietly on this forum being non professional.
Fourth cnc is just a tool so we can make a living. It is better to be really good with tools than try and fumble thru with janky robots. Your printer is a really good intro cnc, use it.