Anisotropy of the dimensional variation of sintered parts: a predictive model and a statistical evaluation of its reliability.

A model to evaluate the anisotropy of the dimensional variation of sintered components has been developed in previous works. The procedure evaluates the anisotropy coefficient of an axisymmetric part starting from the volumetric change and the characteristic dimensions of the sample geometry, this coefficient is used by the model to predict the dimensions of the sintered part. Combining the dimensional changes expected for simple geometries, a procedure to compute the dimensional changes of a multilevel component has been proposed. In this work the model has been validated comparing the predicted dimensions to the actual ones considering a chromium steel mechanical component. The component is a three level rotor sintered at five different temperatures, 1150°C, 1200°C, 1250°C, 1300°C and 1350°C. The parts have been measured with a coordinate measuring machine before and after sintering in a batch furnace. A Monte Carlo like method has been used to evaluate the error distribution and the stability of the model. The results show a narrow distribution of the error which means a good stability and robustness of the model. The worst case scenario predicts an ISO IT9 tolerance class for the sintered dimensions, thus providing an effective level of accuracy.