Statistical Considerations for Real-Time Size Control Systems in Wood Products Manufacturing

Authors

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

Keywords:

Lumber size control, statistical process control, target sizes, control charts, real-time

Abstract

Currently, sawmill machinery companies are developing real-time size lumber size control systems using non-contact laser measuring systems. These systems rely on the application of industrial statistics to large quantities of lumber thickness and width data. Because of the sampling intensity and frequent decision making in real-time systems, there is an increased chance of committing Type I or Type II errors when drawing conclusions if statistical methods are incorrectly applied. There is confusion in the industry concerning the appropriate statistical model to use for lumber size control. This survey of the current literature discusses three distinct methods for calculating and partitioning sawing variation, and thereby calculating control limits for control charts. This paper reviews the statistical foundation and current understanding of industrial statistics for implementing real-time SPC systems and makes recommendations for improvement.

References

Brown, T. D. 1979. Determining lumber target sizes and monitoring sawing accuracy. Forest Prod. J. 29(4):48-54.nBrown, T. D. 1982. Quality control in lumber manufacturing. Miller Freeman Publications, San Francisco, 288 pp.nBrown, T. D. 1986. Lumber size control. For. Res. Lab., Oregon State University Corvalis, Corvalis, OR. 16 pp.nCook, D. F. 1992. Statistical process control for continuous forest products manufacturing operations. Forest Prod. J. 42(7/8):47-53.nGrant, E. L., and R. S. Leavenworth. 1988. Statistical quality control. McGraw-Hill, New York, NY. 694 pp.nHicks, C. R., and K. V. Turner. 1999. Fundamental concepts in the design of experiments, 5th ed. Oxford University Press, New York, NY. 565 pp.nLister, P. 1997. Understanding the relationship between circular saw kerf width, sawing variation, and feed speed. Fifth International Conference on Sawing Technology. October 30-31, 1997. Seattle, WA. Published by Wood Machining Institute, Berkeley, CA. Pp. 17-22.nManess, T. C., and Y. Lin. 1995. The influence of sawkerf and target size reductions on sawmill revenue and volume recovery. Forest Prod. J. 45(11/12):43-50.nMontgomery, D. C. 2001. Introduction to statistical quality control. John Wiley and Sons. New York, NY. 796 pp.nNeter, J., W. Wasserman, M. H. Kutner, and C. Nachtsheim, C. 1996. Applied linear statistical models, 4th ed. Irwin McGraw-Hill, Chicago, 1408 pp.nRyan, T. P. 1989. Statistical methods for quality improvement. John Wiley and Sons, New York, NY. 446 pp.nShewhart, W. A. 1931. Economic control of quality of manufactured product. D. Van Nostrand Company Inc., New York, NY.nSmithies, J. N. 1991. Sawmilling accuracy for bandsaws cutting British softwoods. Forestry Commision Bulletin 96, London, UK. 16 pp.nWang, S. J. 1983. An analytic approach to estimating the increase in lumber recovery due to reduced target sizes and saw kerfs. Forest Prod. J. 33(11/12):53-60.nWang, S. J. 1984. A new approach to calculating target sizes. Forest Prod. J. 34(9):53-60.nWarren, W. G. 1973. How to calculate target thickness for green lumber. Department of the Environment, Canadian Forestry Service, West. For. Prod. Lab. (Forintek Canada), Vancouver, B.C. 10 pp.nWhitehead, J. C. 1978. Procedures for developing a lumber-size control system. Canada Dept. of the Environment, Forestry Directorate, West. For. Prod. Lab. (Forintek Canada), Vancouver, B.C. 15 pp.nYoung, T. M., and P. M. Winistorfer. 2001. The effects of autocorrelation on real-time statistical process control with solutions for forest products manufacturers. Forest Prod. J. 51(11/12):70-77.n

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Published

2007-06-05

Issue

Number 3 / July 2002

Section

Research Contributions

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