Ford's Woodhaven Stamping operation had been seriously involved in a Total Quality Excellence Program for 36 months. They had achieved considerable improvement in all nine targeted performance measures, but had hit a plateau, still more than 20% behind the world class competitive benchmark. There was no clear explanation as to why, and despite additional effort, performance measures had stopped improving. Our initial investigation revealed that the complexity of improving 9 independent processes had overloaded the system and created a drop in the performance of the plant as a whole.

The explanation is simple. In an interdependent system, individual variables can only be improved independently up to a point, whereupon the slack in the system is used up. In Woodhaven, each of the 9 'independent' process improvement teams had assumed they were the only game in town, and tried to sub-optimize their respective functions (optimize each separately, thereby suboptimizing the whole). The teams had produced a series of incompatible and often conflicting solutions for each of the following concerns: safety, material flow, inventory, waste reduction, 'hit to hit', die change, total plant maintenance, yield, and time cycle. Initial improvements had depleted the existing slack and subsequent solutions were being patched on, resulting in a drag on throughput. Reaching a plateau before achieving the desired target is a clear indication that a system has reached its maximum potential and further improvements can only come from a complete redesign of the production process.

A total process redesign was initiated with the leadership of the plant manager and the participation of all his direct reports. A single design for the throughput process emerged which addressed all nine areas of concern and moved the system beyond the desired targets, hitting several birds with one stone and thus reducing complexity and overload and generating enough spare capacity for new product introduction.

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