Monitoring and diagnosing dependent process steps using VSI control charts

Abstract The paper proposes the variables sampling interval (VSI) scheme to monitor the means and the variances in two dependent process steps. The performance of the considered VSI control charts is measured by the adjusted average time to signal derived by a Markov chain approach. An example of the process control for the metallic film thickness of the computer connectors system shows the application and performance of the proposed VSI control charts in detecting shifts. Furthermore, the performance of the VSI control charts and the fixed sampling interval control charts are compared via the numerical analysis results. These demonstrate that the former is much faster in detecting shifts. Whenever quality engineers cannot specify the values of variable sampling intervals, the optimal VSI control charts are recommended. Furthermore, the impacts of misusing Shewhart charts to monitoring the process mean and variance in the second process step are also investigated.

[1]  Marion R. Reynolds,et al.  Variable Sampling Interval X Charts in the Presence of Correlation , 1996 .

[2]  Mahmoud A. Mahmoud,et al.  On the Monitoring of Linear Profiles , 2003 .

[3]  Marion R. Reynolds,et al.  Monitoring the Process Mean and Variance Using Individual Observations and Variable Sampling Intervals , 2001 .

[4]  William H. Woodall,et al.  Weaknesses of The Economic Design of Control Charts , 1986 .

[5]  Robert V. Baxley,et al.  An Application of Variable Sampling Interval Control Charts , 1995 .

[6]  Marion R. Reynolds,et al.  Optimal one-sided shewhart control charts with variable sampling intervals , 1989 .

[7]  William H. Woodall,et al.  A review and analysis of cause-selecting control charts , 1993 .

[8]  Raid W. Amin,et al.  A Robustness Study of Charts with Variable Sampling Intervals , 1993 .

[9]  Marion R. Reynolds,et al.  Variable sampling intervals for multiparameter shewhart charts , 1989 .

[10]  A. R. Crathorne,et al.  Economic Control of Quality of Manufactured Product. , 1933 .

[11]  Corwin L. Atwood,et al.  Techniques for Uncertainty Analysis of Complex Measurement Processes , 1996 .

[12]  George Tagaras A Survey of Recent Developments in the Design of Adaptive Control Charts , 1998 .

[13]  Acheson J. Duncan,et al.  The Economic Design of X Charts Used to Maintain Current Control of a Process , 1956 .

[14]  J. A. Nachlas,et al.  X charts with variable sampling intervals , 1988 .

[15]  Adhir K Basu,et al.  Introduction to Stochastic Process , 2002 .