Warranty cost improvement of machine tools during the bidding process and operation

In the last decade, reliability improvement warranties (RIW) became increasingly popular with customers of machine tool manufacturers especially in the automotive industry. These RIWs include long term warranties (for up to 10 years) for reliability figures like the Mean Time Between Failure (MTBF). The long warranty period, the stochastic nature of reliability, unknown operational conditions and un certainties regarding the reliability parameters of a component bear the risk of cost through high recourses due to low reliability. The paper shows approaches to lower the risks of high recourses in the bidding process and during operation of machine tools. The methods described in the paper are based on statistical failure analysis with the Weibull distribution and Monte Carlo simulation based warranty prognosis. It is shown that with a good knowledge of the infield reliability of their products, machine tool manufacturers have opportunities to not only calculate but also to lower risks of reliability improvement warranties.