Reliability Testing of Statistical Process Control Procedures for Manufacturing with Multiple Sources of Variation

Authors

  • Thomas C. Maness
  • Robert A. Kozak
  • Christina Staudhammer

Keywords:

Lumber size control, statistical process control (SPC), control charts, lumber manufacturing, simulation

Abstract

Quality inconsistencies can be caused by processes with multiple sources of variation. Therefore, the development of control charts that perform properly for both producer's and consumer's risk can be very complex. This is particularly true for real-time SPC systems that collect a great deal of data through noncontact sensing. In this paper, we demonstrate the use of a Monte Carlo simulation procedure that can be used to test SPC charts for both consumer's and producer's risk, and an experimental design procedure to analyze the results. This procedure is shown to be especially useful where design factors interact to cause high variation in a quality characteristic of a product. The approach is illustrated for a practical problem taken from the lumber manufacturing industry and demonstrates that commonly used industrial practices to control product dimensions lead to erroneous conclusions. To that end, a new mathematical approach that yields the correct results is described. The Simulation / ANOVA procedure described in this paper may have applicability in the control of many other industrial processes.

References

Gaylor, D. W., and F. N. Hopper. 1969. Estimating the degrees of freedom for linear combinations of mean squares by Satterthwaite's formula. Technometrics11(4):691-706.nManess, T. C., C. L. Staudhammer, and R. A. Kozak. 2002. Statistical considerations for real-time size control systems in Wood Products Manufacturing. Wood Fiber Sci.34(3):476-484nManess, T. C., R. A. Kozak, and C. L. Staudhammer. 2003. Applying real-time statistical process control to manufacturing processes exhibiting between and within part size variability. Journal of Quality Engineering.16(1):113-125.nMontgomery, D. C. 1997. Design and analysis of experiments. John Wiley & Sons, New York, NY. 704 pp.nMontgomery, D. C. 2001. Introduction to statistical quality control. John Wiley & Sons, New York, NY. 796 pp.nNeter, J., W. Wasserman, M. H. Kutner, and C. Nachtsheim 1996. Applied linear statistical models, 4th ed. xv, Irwin McGraw-Hill, Chicago, IL 1408 pp.nSAS Institute. 1999. SAS Language Reference: Dictionary, Version 8, Volume 2. SAS Publishing, Cary, NC. 1287 pp.nSmithies, J. N. 1991. Sawmilling accuracy for bandsaws cutting British softwoods. Forestry Commission, London, UK. 16 pp.nWhitehead, J. C. 1978. Procedures for developing a lumber-size control system. Canada Department of the Environment, Forestry Directorate, Western Forest Products Laboratory, Vancouver, BC. 15 pp.nWoodall, W. H., and E. V. Thomas. 1995. Statistical process control with several components of common cause variability. IIE Transactions27 757-764.n

Downloads

Published

2007-06-05

Issue

Number 3 / July 2004

Section

Research Contributions

License

The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:

1. All proprietary rights other than copyright, such as patent rights.

2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.

3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.