potential for straight-line ripping prior to crosscutting hardwood lumber

This study tested the potential for increased part yield from straight-line ripping a single sawline in lumber prior to a standard crosscut-first operation. A database of digitally described lumber of grades FAS, 1C, 2C, and 3AC provided the study lumber. Lumber cut-up was performed by computer simulation. Single rip sawlines were repetitively placed in the lumber at 1/4-inch intervals. The two resulting strips from each sawline placement were then processed by a crosscut-first system. The unripped lumber was also cut by simulation of the crosscut-first system. Yields for the two systems were compared. A significant percentage increase of 3.9 percent was obtained by the single rip sawline system for those boards that showed increased yield. Boards without a yield increase need to be excluded from those boards receiving a single rip sawline to prevent significant yield loss. Yield was very sensitive to sawline location, with 1/4 inch errors in sawline placement offsetting the 3.9 percent yield increase. Therefore, a single rip sawline system requires very accurate sawline placement. This would necessitate lumber scanning followed by computer analysis in which all possible rip sawlines are tested at 1/4-inch intervals.