Measurement of Geometric Features of Spherical Objects

Spherical shaped objects are some of the most interesting and difficult to measure objects in dimensional metrology. Made of steel, alloys, ceramics, glass, rubber or plastics, they are important elements of precision bearings, pumps, valves, flow meters, medical, measuring, automotive, aerospace and other equipment, used for polishing, grinding, etc. Quality requirements, including their geometric accuracy, are high. A spherical object is defined geometrically by a centre, radius, and spherical spatial surface. There are no uniform rules and definitions for measuring these characteristics, and there is no standard definition of a form deviation. A number of solutions and publications are known to address the problem in practice, which, for the time being, do not allow a uniquely substantiated definition of the derived geometric elements and methods for their measurement. Full measurement of the deviation from sphericity, for example, is impossible. The question of the type of its associated element satisfying certain standard criteria remains open. The accuracy and reliability of measuring spherical objects is related to finding a reasonable solution to the outlined issues.