Evaluation of sphericity error from coordinate measurement data using computational geometric techniques Original Research Article

The measurement data of a spherical component can be obtained from inspection devices such as coordinate measuring machines (CMMs). The sphericity error is evaluated from such coordinate data based on the minimum circumscribed sphere, the maximum inscribed sphere and minimum zone spheres. Appropriate methods based on the computational geometry have been developed to establish these assessment spheres. The present methods start with construction of 3-D hulls. The 3-D convex outer hull is established using the computational geometric concept presently available. For establishing a 3-D inner hull, a new heuristic method is suggested in this paper. A new concept of 3-D equidistant (ED) line is introduced in the present method. Based on this concept, the authors have constructed 3-D farthest and nearest equidistant diagrams for establishing the assessment spheres. Algorithms proposed in the present work are implemented and validated with the simulated data and the data available in the literature.