A Model for the Sawing and Grading of Lumber According to Knots


  • Hugo Lemieux
  • Michel Beaudoin
  • Frančois Grondin


Model, sawing, grading, knots, structural lumber


As a means to determine the grade improvement potential of black spruce, a sawing and grading model is presented. It uses an analytical representation of the knots, the boards, the log, along with the National Lumber Grades Authority Visual Strength Grading Rules, as a means to grade the sawn lumber according to the knots. A simulation was performed using knot data collected on the surface of a black spruce log. The log was then sawn, and the data were collected on the board surfaces. The simulation shows that, in general, the model approximates well the knot diameter on the boards using data collected on the log's surface, but the "equivalent diameter" as calculated from the NLGA Rules underestimates it.


Aune, J. E., and P. K. L. So. 1991. Log scanner. U.S. Patent 5 023 805. U.S. Patent Office, Washington DC.nChang, S. J., and S. Guddanti. 1995. TOPSAW-HW: A training and optimisation system for sawing hardwood logs. Paper presented at the XX IUFRO World Congress, August 6-12, 1995. Tampere, Finland.nHarless, T. E. G., F. G. Wagner, P. H. Steele, F. W. Taylor, V. Yadoma, and C. W. McMillin. 1991. Methodology for locating defects within hardwood logs and determining their impact on the lumber-value yield. Forest Prod. J. 41(4):25-30.nHodges, D. G., W. C. Anderson, and C. W. McMillin. 1990. The economic potential of ct scanners for hardwood sawmills. Forest Prod. J. 40(3):65-69.nHoibo, O. A., G. I. Vestol., H. J. Sundby, and D. E. Molteberg. 1996. Modelling knottiness and knot characteristics of Norway spruce (Picea abies (L.) Karst). The influence of diameter and height growth on knot characteristics. IUFRO Biological Improvement of Wood Properties, August 26-31, 1996, Kruger National Park, South Africa.nJozsa, L. A., and G. R. Middleton. 1994. A discussion of wood quality attributes and their practical implications. Forintek Canada Corporation Special Publication No. SP-34. Vancouver, BC. 41 pp.nMadsen, B. 1992. Structural behaviour of timber. Timber Engineering Ltd., Vancouver, BC. 446 pp.nMinistère des Ressources Naturelles Du Québec. 1996. L'industrie québécoise des produits du bois-situation et perspectives d'avenir. Les publications du Québec, Québec, Canada. 225 pp.nNational Lumber Grading Authorities. 1996. NLGA Visual Strength Grading Rules for Lumber. National Lumber Grading Authorities. Bumaby, BC.nPham, D. T., and R. J. Alcock. 1998. Automated grading and defect detection: A review. Forest Prod. J. 48(4): 34-42.nPnevmaticos, S. M., and P. Mouland. 1978. Hardwood sawing simulation techniques. Forest Prod. J. 28(4):51-55.nPnevmaticos, S. M., P. E. Dress, and F. R. Stocker. 1974. Log and sawing simulation through computer graphics. Forest Prod. J. 24(3):53-55.nSamson, M. 1993. Method for assessing the effect of knots in the conversion of logs into structural lumber. Wood Fiber Sci. 25(3):298-304.nSamson, M., I. Bindzi, and L.-M. Kamoso. 1995. Mathematical modelling of the first cut of a sawlog—Part II: Cutting of the knot envelope. Laval University Unpublished. 22 pp.nSamson, M., I. Bindzi, L.-M. Kamoso. 1996. Mathematical representation of knots in tree trunks. Can. J. Forest Res. 26(2): 159-165 (In French).nSteele, P. H., F. G. Wagner, L. Kumar, and P. A. Araman. 1993. The value versus volume yield problem for live-sawn hardwood sawlogs. Forest Prod. J. 43(9):35-40.nSteele, P. H., T. E. G. Harless, F. G. Wagner, L. Kumar, and F. W. Taylor. 1994. Increased lumber value from optimum orientation of internal defects with respect to sawing pattern in hardwood sawlogs. Forest Prod. J. 44(3):69-72.nThomas, E., and K. Bush. 1998. Log scanning: An alternative approach. ScanPro 1998, November 4-6 1998, Vancouver, BC, Canada.nTodoroki, C. 1996. Developments of the sawing simulation software, AUTOSAW linking wood properties, sawing and lumber end-use. IUFRO WP S5.01-04, Biological Improvement of Wood Properties. South Africa.nVäisänen, H., S. Kellomäki, P. Oker-Blom, and E. Valtonen. 1989. Structural development of Pinus sylvestris stands with varying initial density: A preliminary model for quality of sawn timber as affected by silvicultural measures. Scan. J. Forest Res. 4:223-238.nWagner, F. G., F. W. Taylor, D. S. Ladd, C. W. McMillin and F. L. Roder. 1989. Ultrafast CT scanning of an oak log for internal defects. Forest Prod. J. 39(11/12):62-64.nWagner, F. G., F. W. Taylor, P. H. Steele, L. Kumar, and D. Butkovic. 1991. Computer grading of southern pine lumber. Forest Prod. J. 41(2):27-29.nWagner, F. G., F. W. Taylor, C. E. Keegan, R. D. Fight, and S. Willits. 1998. Potential for small-diameter sawtimber utilization by the current sawmill industry in western North America. Forest Prod. J. 48(9):30-34.nZeng, Y., S. Randhawa, and J. Funck. 1996. An expert system for softwood lumber grading. Computers Industrial Eng. 31(1/2):463-466.n






Research Contributions