Manufacturing processes for chemical products are often defined in terms of process control parameters and their center values and control ranges. Center values are optimal values found through, e.g., parameter design; control ranges are often determined empirically. Despite such process control, however, the manufactured products are sometimes out-of-spec. When this happens, steps must be taken to keep the problem from recurring: for example, by narrowing the control ranges of the parameters

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... volved. Until the problem is eliminated, all outgoing products have to be inspected before shipment. To maintain stable high-volume production, solutions to such problems need to be found quickly. This paper describes how the MT-system was used to set process control values in order to prevent the recurrence of a problem of out-of-spec coloration that could not easily be reproduced in the laboratory. Adjusting the production process to these values solved the problem. This case study demonstrated the usefulness of the MT-system in process analysis, and established an analytic procedure. Because of the restricted applicability of the MT-system, however, use of the T (1) method was also studied, and the conclusion was reached that the T (1) method might also offer solutions to such problems.