Statistical estimation of variation transmission model in a manufacturing process

This article describes a method for obtaining a variation transmission model in a multi-stage manufacturing process in situations in which the characteristic that defines the quality of the product is an independent variable which variation is the consequence of the one generated and transmitted through the different process stages. The method uses regression analysis to obtain models that relate the quality characteristic to process variables, statistical process control techniques to estimate the variance of the variables and the analysis of variance to estimate the variance components from the observed data and to verify that data come from a stable process. This method can be applied to processes where the quality characteristics are different at each stage (a usual situation in chemical processes) and in cases where not all the process variables can be measured directly. The model also includes the measurement errors both of the quality characteristic and of the process variables. The new proposed approach has been applied to validate its suitability in a ceramic tiles manufacturing process.