Optimum edging and trimming of hardwood lumber

Before the adoption of an automated system for optimizing edging and trimming in hardwood mills, the performance of present manual systems must be evaluated to provide a basis for comparison. A study was made in which lumber values recovered in actual hardwood operations were compared to the output of a computer-based procedure for edging and trimming optimization. The optimization procedure was based on National Hardwood Lumber Association grading rules and market prices for green lumber. Using a sample of 120 red oak boards obtained from three sawmills in southwest Virginia, it was found that the respective mills recovered only 78, 65, and 62 percent of the value yielded by the optimization procedure. Given the level of value recovery actually attained by sawmills, it was concluded that substantial increases in value can be expected from optimizing edging and trimming. Other aspects of interest were investigated, such as the quality (grade) of lumber that benefitted most from optimization, the effect of volume loss on value recovery, and the relative impact on lumber value if each operation were optimized independently of each other. Edging and trimming operations have been identified in several sawmill studies as processing steps where significant losses occur in lumber volume and/or value due to non-optimum operating procedures (2,3, 13). In softwood lumber manufacturing, edger and trimmer optimizers have been shown to increase volume recovery at these machine centers (1,8, 10). The need for edger and trimmer optimizers is now being recognized in hardwood sawmilling (4). It is hypothesized that benefits in the form of increased lumber value and/or volume may also be expected if optimization technology were applied to hardwood edging and trimming. Before the development and adoption of an automated system for optimizing hardwood edging and trimming operations, the performance of existing manual systems should be evaluated. The primary goal in the move toward automation is to show that improvements can be made over the actual output of manual systems. Addressing this goal, the specific objectives of this study were to: 1) develop a general procedure for estimating the optimum edging and trimming solution for maximizing the lumber value obtained from unedged/untrimmed boards; 2) determine the difference between the value of 4/4 red oak lumber obtained with optimum edging and trimming, and that recovered in actual sawmilling operations; 3) compare the lumber value obtainable when only edging is optimized to the value obtainable when only trimming is optimized; and 4) identify the edging and trimming errors that most significantly contribute to the difference between the theoretical optimum and actual lumber values. Methods and materials The general approach of the study was to obtain a sample of unedged/untrimmed boards from several hardwood mills, collect data pertinent to lumber value evaluation, develop a computer procedure to estimate The authors are, respectively, Research Associate and Assistant Professor, Dept. of Wood Sci. and Forest Prod., VPI&SU, Blacksburg, VA 2406 1-0323; and Project Leader, USDA Forest Serv., Southeastern Forest Expt. Sta., Brooks Forest Prod. Center, VPI&SU, Blacksburg, VA 24061-0503. The authors wish to acknowledge the USDA Forest Serv., Southeastern Forest Expt. Sta., for partial financial support. This paper was received for publication in February . ©Forest Products Research Society 1992. Forest Prod. J. 42(2):8-14.