Abstract: Demand prediction model for spare parts with Weibull distribution involves multiple infinite series, therefore, spares demand calculation is a difficult issue. The approximate calculation method generally used is often subject to large errors. According to the principle of renewal function, the approximated demand calculation method for spares of Weibull distribution using piecewise function to approximate the renewal function is proposed. It effectively avoids the issue of computational complexity for spares demand prediction. Theoretical analysis shows that the proposed approximated algorithm ensures the calculation result of spares demand is less than that of engineering approximation algorithm. According to the given example, the simulation verifies that the proposed approximation algorithm has a better approximation effect, meets the practical support demand as well as the engineering demand.

Key words: renewal process, renewal function, spare parts with weibulldistribution, spare demand function