The effects of lumber length on part yields in gang-rip-first rough mills
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Forest Products Journal 52(5):71-76
The lumber processed in most rough mills typically arrives from vendors in packages of random width boards with lengths ranging from 8 to 16 feet. However, little attention has been given to analyzing how differences in board lengths affect rough mill yield given varying part-prioritization strategies and cutting bill scenarios. The objective of this study was to determine if the same clear part yield could be obtained from the same volume of lumber and grade mix of shorter boards (7 to 8 ft.), medium-length boards (11 to 12 ft.), and long boards (15 to 16 ft.). This study uses simulation (ROMI-RP 2.0) and applies an experimental design that reflects actual gang-rip-first rough mill operations found in furniture, cabinet, and dimension industries. Two cutting bills representing "easy" and "hard" degrees of difficulty were used. Three part-prioritization strategies were applied to reflect both standard rough mill practices and an optimizing strategy. Five randomized replications from each length sort were run for both cutting bills and for each part-prioritization strategy. A total of 90 simulations were used in the analysis. Total part yield was the dependent variable in this study. Statistical analysis indicated that significant differences in part yields existed between the three lumber length sorts for both cutting bills and for all three part-prioritization strategies. Average part yields across part-prioritization strategies increased consistently, by more than 5 percent overall, for both cutting bills, as board length increased.
Hamner, Peter C.; Bond, Brian H.; Wiedenbeck, Janice K. 2002. The effects of lumber length on part yields in gang-rip-first rough mills. Forest Products Journal 52(5):71-76