Volume and value variation with opening face position : An investigation with pruned softwood logs

This study examined the effect of opening sawline position on the volume and value of timber yield. Yield was generated from the simulated sawing of 12 pruned softwood logs. Each log underwent a series of simulations; half utilized a volume optimizing edger, and the other half utilized a grade (value) optimizing edger. With the exception of placement of the initial opening sawline, the simulations used identical sawing conditions. An initial opening sawline was made at the first opening position yielding the smallest acceptable piece. This Minimum Opening Face (MOF) position differed from log to log, depending on the unique non-regular form of each log. In subsequent simulations, the opening sawline was successively shifted by 1-mm increments toward the center ofthe log with final simulations 44 mm away from MOF. For each simulation, the timber was graded using criteria for cuttings and appearance grades and valued according to both grade and dimensions. The simulations demonstrated that both volume and value yield vary with different opening sawline placements. Value yields obtained from grade-optimized edging added about 16 percent in value over and above those obtained from volume-optimized edging. Furthermore, the difference between minimum and maximum value yields from grade optimization was about half that demonstrated by volume optimization. This suggests that current optimization techniques and grade scanning technologies can achieve solutions near the theoretical maximum value. However, internal defect scanning is required to determine that opening face yielding maximum value. Should that become commercially viable, this study indicated that a further increase in value of about 3 percent is possible.