TABLE OF CONTENTS Manufacturing systems are nowadays geared up to meet the challenges of a quality-based competition. Process capability studies and analyses have become critical issues in process control; indeed a number of guidelines are available for process capability assessment. Moreover, certain conditions such as normally distributed output, statistical independence of observed values and the existence of only random variation resulted from chance causes are stipulated for this assessment. All these conditions may not be fully satisfied in a practical set-up and departures are quite likely to occur. Tool wear is, evidently, constitutes a dominant and inseparable component of variability in many "machining" processes, and hence it represents a systematic assignable cause. Process capability assessment in such cases may become a bit tricky since the standard procedure may not provide accurate results.
Process capability studies play an important role in the process control since they assist to decide whether a manufacturing process is suitable and the applications meet the necessary quality standards. The intensified quality-based competition has shifted the focus from the product control to the process control in manufacturing industries. The assessment of process capability, which now appears to be quite simple, involves significant dimensions in a practical set-up. This is due to the fact that some of the conditions necessary to establish process capability are not fully satisfiable. These conditions stipulate that the process has to be under statistical control, that the process output has to follow the normal distribution, be free of assignable causes, and the observed values...
