The importance of assessing downtime cost related factors towards an optimised machine tool calibration schedule

Reducing downtime and assuring a high degree of accuracy of production machines, especially
machine tools, have become increasingly important as the demand for higher production rates and
closer tolerance continues to grow. The growing understanding of the importance of both calibration and maintenance in the evolving industrial scenario and the technological advancements of recent years has yielded the development of advanced metrology equipment and predictive maintenance programs. Predictive maintenance and similar programmes are tools that have been designed to reduce downtime by avoiding unpredictable machine failures. These programmes have been adopted in some industries to improve operational efficiency and reduce machine breakdown. However, extensive diagnostic procedures can take machines out of service for longer periods than are acceptable for some manufacturers. Studies in the field of predictive maintenance have resulted in cost calculations for the downtime associated with machine failure. Models have been presented to determine optimal intervals between repairs by minimising global maintenance costs. However, very little work has concentrated on optimising the frequency of machine tool calibration by assessing the downtime cost considering the contribution of both technical and commercial factors. This paper give an introduction to causes of machine tools failures with respect to production of
non-conforming parts and the importance of calibration and then it addresses the key factors to a cost function parameters that forms the basis of a strategy for scheduling machine tool calibration which takes into account these influences on part tolerance.