When three dimensional machining is performed with a numerically controlled milling machine, then it is necessary to make use of cutter centre point programming because radius correction for these machines is possible in two dimensional context only. With the rapid development of numerically controlled units it is
possible now to use parameter programming for the development of three dimensional spaces which was possible only with computer
aided design software some two years ago. An exceptional visualization of the relationship between cutting surface and cutter position as well as a sound mathematical background is necessary to enable accurate programming of three dimensional spaces.