Abstract: To test the machining accuracy distribution of CNC milling machining center， an orthogonal experimental scheme was presented on the basis of the orthogonal test design theory and the characteristics of CNC machining technology. The scheme was used to machine variable diameter cams and then the line profiles of the cams were simulated using Matlab. The results showed that the line profile accuracy has a normal distribution. The relatively larger line profile errors， R2 and R5， were analyzed using the extreme difference analysis method in order to study the influence of machining parameters. The profile tolerance value should be different for every arc of the same part.

Key words: orthogonal test, CNC milling machining center, line profile, Matlab, normal distribution