Setting simultaneous specifications on multiple raw materials to ensure product quality and minimize risk

Establishing meaningful multivariate specification regions on the multiple properties of a single raw material has been presented and illustrated by Duchesne & MacGregor Duchesne and MacGregor (2004) . However, the manufacture of most final products usually involves the use of many raw materials each with multiple measured properties and from different suppliers. Setting specifications separately on each of these materials is unreasonable since it is the simultaneous combination of the properties of all the materials that will affect final quality. This paper presents an approach to determining the acceptability of new lots of raw materials from multiple suppliers and of assessing the suitability of combining specific lots of materials currently in inventory that will minimize the risk of manufacturing a poor quality product. Multivariate statistical models based on PLS are used to determine the importance of all the properties of each of the materials and to develop the specification methodology. Use of the models for achieving improved control over the product quality is also discussed.