The influence of lumber grade on machine productivity in the rough mill

Lumber grade effect on hardwood-part processing time was investigated with a digitally described lumber database in conjunction with a crosscut-first rough mill yield optimization simulator. In this study,the:digital lumber s ample was subdivided into five hardwood lumber grades. Three cutting bills with varying degrees of difficulty were cut. The three cutting bills and th e five grade sorts were input into the rough mill simulator. Ten randomized replications were run for each of the lumber grade/cutting bill combinatio ns. These 10 were used in the statistical analysis. The dependent variable for each replication was the number of cuts required at each saw (crosscut, straight-line rip, and salvage). By counting the number of cuts and not me asuring actual operator times, as in other studies, operator variation was eliminated from the experiment. The lumber database and the rough mill simu lator isolated the effect of lumber grade on part processing rates. The ana lysis indicated that significant differences existed among the lumber grade s tested and the number of cuts required to fill the three cutting bills. A s expected, the general trend showed that as lumber grade improved, the num ber of required cuts decreased. This trend was true across the three cuttin g bills and at each of the saws.