Tube Parts Form And Position Error Detection Methods

Roundness error and symmetry error are the important guidline to evaluate the geometrical deviation of parts, and there are many methods to measure and evaluate them, so as to adapt to different parts and kinds of precision. However, especially the methods for roundness error are mostly point to rotary work piece whose cross section is formal circle, but seldom people mention to the cross section which is non-formal circle.A new method to get the geometrical deviation of cylinder parts whose cross section is incomplete circle is given in the dissertation. Avoiding the shortness of the usual directe contact methods that uses the roundness tester or coordinate measure machine but can't get the cross section of the part whose cross section is non-full circle; here, use the laser optical displace measurement which operate with high precision and non-contact style can easily get the distance of every measured points on the surface of part and the part center, then the measurement data is translated from the Rectangular Coordinates System and the Polar Coordinates System. Thus, the surface profile of part can be fit with these measured discrete points. Then the error evaluation system is set up according to every method of data processing: four methods to evaluate rondness error- Least squares mean circle, Minimum District Method, Minimum circumscribeb incircle, Minimum Mixtilinear incircles; symmetry torlerance; ridge width- inflexion judge. VC++ flat is also used to realize the visualization of the evaluating operation interface and the result.Use the high precision non-contact displacement measure instead of contact measure, then programme to perform the detection of erery manufacture error item. Thus, the precision is heighten. Realize the function to get the roundness error and geometrical deviation of the parts whose cross section is an incomplete circle. Also effectly resolve the problem when detect the parts which are so hot or soft to contact its surface, so can well adapt circumstance.