Statistical Quality Control, 7th Edition

PART 4

Other Statistical Process-Monitoring and Control Techniques

Part 3 focused on the basic methods of statistical process control and capability analysis. Many of these techniques, such as the Shewhart control charts, have been in use for well over 75 years. However, the increasing emphasis on variability reduction, yield enhancement, and process improvement along with the success of the basic methods has led to the development of many new techniques for statistical process monitoring and control. This part contains four chapters describing some of these techniques. Chapter 9 presents the cumulative sum (CUSUM) control chart and the exponentially weighted moving average (EWMA) control chart. These procedures are not really new, since they date from the 1950s, but they are generally considered somewhat more advanced techniques than the Shewhart charts. As we will see, the CUSUM and the EWMA offer considerable performance improvement relative to Shewhart charts. CUSUM and EWMA control charts are very useful in phase II process-monitoring situations. Chapter 10 is a survey of several univariate process control techniques, including methods for short production runs and monitoring techniques suitable for processes in which the data are autocorrelated. Chapter 11 is an introduction to multivariate process monitoring and control, techniques that are applicable when two or more related process variables are of interest. Chapter 12 presents techniques for process control by feedback ...