A Revised Model For The Cost Of Quality

Traditionally, process improvement is considered a defect prevention effort. Current cost models consider the coupled effect of both prevention and appraisal costs on the cost of failure. This paper proposes a new model for the cost of quality, which captures the value of continuous process improvement in achieving economic operation. The model is developed to incorporate two cost functions. The first accounts for quality related costs incurred while maintaining a stable level of operation, while the second accounts for the cost of process improvement. Using incremental economics, the two cost functions are assembled and an economic criterion for evaluating improvement alternatives is developed. Numerical examples are used to illustrate potential applications and performance of the model. © Emerald Group Publishing Limited

The Economic Design Of X̄ Charts: A Proactive Approach

It has long been recognized that poor quality can only result in higher costs. Yet, the idea of reducing cost through better quality is not fully realized. Current models for the economic design of control charts provide strategies to maintain existing quality levels. In this research, a comprehensive cost model is developed to incorporate two cost functions. A reactive function, which accounts for all quality related costs incurred while maintaining a stable level of the process, and a proactive function, which accounts for the cost of process improvement. Using incremental economics, the two cost functions are assembled to allow an evaluation of process improvement alternatives based on their economic worth. Procedures for obtaining economically optimum designs for controlling the process mean are developed and designed experiments are utilized to investigate model performance over a wide range of input parameters. The results indicate that the model is sensitive to changes in 13 parameters, especially when the magnitude of the process shift is small. Copyright © 2004 John Wiley & Sons, Ltd