This paper describes and analyses several one-sided lower protection control charts with pre-limits and run rules for the control of a specific process parameter. In particular, it is shown that the decision-making criteria associated with each control chart may be described in terms of discrete times, homogenous Markov processes with a finite number of states. Explicit solutions are then worked out for the mean value (ARL) and the variance (VRL) of the run length distribution. Then, the capability index C_p is defined, and the use of such charts for process monitoring at production start-up is proposed and discussed in some detail, mostly in numerical terms. The notion of process acceptance probability is also introduced, and an alternative criterion for the assessment of chart performance is proposed.
Control charts with pre-limits and run rules for the estimate of the Cp capability index
ISAIA, Ennio Davide
1999-01-01
Abstract
This paper describes and analyses several one-sided lower protection control charts with pre-limits and run rules for the control of a specific process parameter. In particular, it is shown that the decision-making criteria associated with each control chart may be described in terms of discrete times, homogenous Markov processes with a finite number of states. Explicit solutions are then worked out for the mean value (ARL) and the variance (VRL) of the run length distribution. Then, the capability index C_p is defined, and the use of such charts for process monitoring at production start-up is proposed and discussed in some detail, mostly in numerical terms. The notion of process acceptance probability is also introduced, and an alternative criterion for the assessment of chart performance is proposed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.