Hi James,
Forgetting about ardunios, mach4 etc it goes like this:
1) You design something in CAD, this could be a 2D thing or a 3D thing
2) You export the CAD into a CAM (computer added manufacture) program. The CAD and CAM could be integrated and not separated eg rhino3D CAD and Rhino3d CAM are integrated like Fusion360 they are inside the same environment. I use three different CAD programs and import the CAD into a free standing CAM (mechsoft mill or UCCNC) depending on what sort of job it is
3) The CAM program is used to create G code and M code. Gcode is a toolpath which is a string of 3D co-ordinates that tells the machine where to move the tool to. This path can be checked or simulated in toolpath checking software. M code are commands like turn spindle on and off, turn on lights turn on/off air blast etc
4) Once you are happy with the Gcode this is imported into a machine controller. eg mach4, UCCNC, acorn etc etc there are many controllers around
5) The machine controller turns the Gcode or NC code into machine impulses and co-ordinates the axes, it sends out a stream of impulses to each motor in the system
6) But these impulses are also feed through a motion controller. This looks ahead and identifies corners and stops and controls the velocity of the motors. If there was no motion controller (like a UC100 that I use) the machine would crash as it doesn't know that a corner is coming and needs to slow down
7) Once all of this is done the tool moves at the speed it should, the path it should and you get a result.
Cheers Peter
Regarding other requests 1) making a mill to cut aluminium is a tough call for a newbie plus cutting dry is fraught with difficulties. Do lots of reading in the forum about this requirement. You do say a mill so it is mainly for metalwork 2) ER collets are not quick release? The tool has to be set every time. 3) look at Taig mills or similiar... if these are too small then look at mills of a size you need and have a good think... Mills are large chunks of metal, maybe think about converting a small manual mill to cnc then lots of the hard work is done...