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Radius compensation (aka cutter comp)

Radius compensation is a CNC programming method using the G41 and G42 code words. The radius of the cutter being used is stored in controller memory address (not programmed). The G41 command tells the controller to offset the cutter one radius to the left of every coordinates it reads. G42 offsets to the right. The advantage is that the programmer can develop a tool path that exactly represents the geometry of the part (a much simpler task than calculating the offset of the tool at every point) and then allow the controller to determine what the true coordinates for the spindle should be given a cutter of a known (stored) radius.

This means that a part can be machined with a .250 dia. end mill or a .500 dia. end mill or any other size of end mill from just one program.

The determination of left and right can be confusing. Examine the graphic below. See also radius compensation left and radius compensation right