Effect of Hardwood Sawmill Edging and Trimming Practices on Furniture Part Production
In a recent edging and trimming study at three hardwood sawmills, it was observed that the lumber volume produced was approximately 10 percent less than would be necessary to make the most valuable lumber. Furthermore, the excess portion of wood that was removed from the edging and trimming process contained a large percentage of clear wood. In light of rising costs and increasing environmental concerns, the option of producing furniture parts from unedged and untrimmed boards is explored. This research investigates the potential furniture part yields from unedged and untrimmed boards compared to both optimal and actual edging and trimming practices. The resulting volume of cuttings from unedged and untrimmed boards was found to be 25 percent higher than from the actual edged and trimmed lumber produced at the mills.
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.
- c o r y - a computer program to determine furniture cutting yields for both rip-first and crosscut-first sawing sequences
Computer simulation is the most economical method for comparing the rip-first and crosscut-first sawing sequences used in hardwood furniture rough mills. However, no single computer program existed which could be adequately modified to compare these two operations with identical logic without excessive computer time and cost. Program CORY was designed to perform this task and to improve the yield from short low-grade lumber. CORY's approach is different from other yield programs, because defect data is converted into clear areas only once, and then this information is used in a "divide and conquer" algorithm to obtain a sawing solution. The program can emphasize different cutting bill lengths by weighting the length with an exponential function. A study of program effectiveness variables indicated that only the kerf lines from the largest two weighted clear areas need to be investigated to improve yield, and that only the five largest weighted clear cuttings need to be used to determine the best sawing solution. 
A comparison study of CORY and the USFS program YIELD was performed on a twenty-five-board sample. CORY produced 2.71% to 4.24% better yield, depending on the processing options specified. It also executed an average of sixty-three times faster, which presents the possibility of using this program in future rough mill process control. 
A demonstration study of CORY was performed on a 400-board sample. Yields were determined for the whole sample and for individual cutting length classes for four combinations of first-cut operation and weighting factor. Results showed that crosscutting and ripping first both produce equal total yields. However, ripping first has more recovery in the longer cutting bill lengths, and crosscutting first has more recovery in the shortest lengths. An increase in weighting factor always decreases total yield but increases recovery in the longer, more valuable cutting bill classes.