Simple and efficient algorithms for roundness evaluation from the coordinate measurement data

A common problem of quality control and inspection of circular parts is the measurement of their roundness. Recently, the coordinate measuring machines (CMMs) have been used to measure roundness errors by collecting a large number of points from the profile of the rounded parts to meet the international standards. Direct evaluation of roundness from this large number of pointes is complex and time consuming. Therefore, efficient algorithms should be designed to meet the standards and to simplify and accelerate the computation process. This paper introduces simple and efficient algorithms to evaluate the roundness error from the large number of points obtained by CMMs using three internationally defined methods: Minimum Circumscribed Circle (MCC), Maximum Inscribed Circle (MIC) and Minimum Zone Circles (MZC). A software has been developed using C++ to apply these algorithms on the data obtained by CMMs. The developed algorithms were verified by comparing their results with the results obtained by a commercial instrument and the maximum variation between the two results did not exceed than ±2.27%. The efficiency of the introduced algorithms was verified in terms of computation time and the results proved the efficiency of the developed algorithms.