Recent advances in scanning technology have enabled the detection of surface defects in green boards. This report is the second phase of a project that was initiated to investigate the benefits of surface defect scanning (grade scanning) on the value of lumber that can be recovered from optimized edgers. The first study focused on BC Interior mills and found that little or no potential increase was available. In this study, the benefits for mills processing large logs into high value products (e.g. BC Coastal sawmills) were investigated. Sixty-six hemlock cants were evaluated, with cant widths from 12 to 27 inches - large enough to allow multiple sawing solutions. After a sawing solution was generated for each cant by an optimized shifting-saw gang edger, using only profile scanned data, a grader, taking visible defects into account, proposed alternate sawing solutions. The values of all sawing solutions were calculated and for 76% of the cants, a sawing solution proposed by the grader was more valuable than the one generated by the optimizer.
The study found that an average increase of 29% in the value of large cants was available when edging decisions took surface defects into account, in comparison with the value resulting from optimization based on cant profile alone. However, it should be noted that the accurancy of vision systems will likely be less than that of a human grader so the actual gains will likely be somewhat lower.