Method of controlling the effect of raw materials on manufacturability

A method of controlling the effect of raw material constituents on a product produced by a manufacturing process, the product being manufactured using a plurality of constituents and having specified product performance characteristics, the manufacturing process having a constituent selection stage in which the constituents are selected in accordance with the product being manufactured, the method comprising the steps of:

• a) defining a set of properties for each of the constituents which affect the product performance characteristics;
• b) sampling data relating to the set of properties of the constituents from product produced by the manufacturing process;
• c) defining a model using the sampled data to provide a reference position for a combination of the constituents which provides good product from the manufacturing process, the model being defined using a multivariate statistical process control technique in terms of parameters T.sup.2 and Q.sub.res, the model including a series of loadings which weight the initial measured properties of the constituents, each of the loadings having a score resulting from the measured properties of the constituents, where T.sup.2 is Hotelling's T.sup.2 parameter and Q.sub.res is an additional parameter representing the systematic non-random variability not captured by the model
• d) applying limits to the model indicative of out-of-control conditions;
• e) monitoring the constituent selection stage for out-of-control conditions;
• and
• f) taking corrective action to select appropriate constituents at the constituent selection stage which provide the specified product performance characteristics of the product.