Computer Numerical Control
A manufacturing process in which pre-programmed computer software dictates the movement of factory tools & machinery, much like a robot. Precision computerized machine tools enable US to safely trim the repaired surfaces of a rim without affecting the strength. Such machining is done to smooth out welded areas and to enhance the original finish of the wheel.
You can always tell machined wheels by the thin lines cut into the aluminum surface during the construction of the wheel. The lines, which resemble those of a CD, are sometimes so fine that they are nearly undetectable. The lines are what produce the rainbow effect that is customary with machined surfaces. Only the outermost surface of the wheel is machined and with some machined wheels, only a portion of the wheel is machined.