CNC machining is an evolution to the milling process. This something which uses rotating cutters in order to remove excess materials from a block of material, whether that is wood, metal or plastic.
There are many different work styles that use this process, as well as a milling crowd that use it as a main function. Most commonly though, this is used for creating precision made parts to a specific size and shape requirement which is dictate by use. The tolerance of CNC machining is incredible. Since machines can be almost fully automated, there is little space for human error, except in the initial planning and programming steps.
Errors will only occur if there is a problem with the metal used, if the tool has become damaged in one way or another, or if an appropriate maintenance is not performed. These machines or 'mills' as they are often referred to as, are now part of machining centers where almost all functions are carried out automatically including changing tools, control, coolants and more.
The machining of the multitasking CNC is incredibly impressive because these machines are capable of achieving a wide variety of extremely complex and extremely delicate jobs that would take a huge amount of time to manually perform.
Turning and milling can now be performed by the same machines in the same space, which means that the cost of manufacturing is considerably reduced.