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Title: Influence of Lumber Volume Maximization in Sawing Hardwood Sawlogs
Author: Steele, Philip H.; Wagner, Francis G.; Kumar, Lalit; Araman, Philip A.
Source: Proceedings of the Forest Industries 21st Wood Technology Clinic Show. pp. 1-26.
Publication Series: Miscellaneous Publication
Description: The Best Opening Face (BOF) technology for volume maximization during sawing has been rapidly adopted by softwood sawmills. Application of this technology in hardwood sawmills has been limited because of their emphasis on sawing for the highest possible grade of lumber. The reason for this emphasis is that there is a relatively large difference in price between the respective grades of hardwood lumber compared to the difference between the softwood lumber grades. Hardwood sawmillers have judged that an attempt to maximize volume would result in value loss to the degree that total value yield would be significantly reduced. While hardwood sawmillers may be correct there has been no data available supporting their expectation that maximizing for volume yield will reduce value yield. The potential volume yield improvement from BOF decisions for sawing hardwood sawlogs is 6.3 percent which is only slightly less than for sawing softwood sawlogs. The BOF technology employs an iterative procedure that tests numerous initial opening face distances from log center for each given sawing pattern. These solutions begin at an opening face position at which the first board face sawn will be of the minimum acceptable dimension. The complete simulated sawing of the log is performed at this minimum opening face position. Subsequent opening face positions are tested by reducing the opening face distance from log center by arbitrarily selected increments. The distance over which opening-face position is tested has been the thickness of one piece of lumber plus kerf width. Maximum-volume yield is attained at the initial minimum opening face position for only a small percentage of BOF solutions. For this reason maximum-volume yield is generally obtained for some opening face position somewhat closer to log center than that of the minimum opening face. In fact, Steele et al. showed that the highest yielding BOF position is generally obtained by centering the sawing pattern in the sawlog. The most frequent of the defect types in sawlogs are knots. Knots are most numerous near log center. Therefore, the movement of sawlines slightly towards log center from a minimum opening face, required for BOF volume maximization, should increase the frequency of sawline intersection with knots. Increased frequency of sawline intersection should result in the yield of lower grade lumber that is of lower value. Past research has examined hardwood log orientation to determine the influence of defect placement on total lumber value with the most recent study showing a significant 10 percent increase in lumber value for best log orientation. All studies, however, opened the sawlog only at the minimum opening face for comparisons of log orientation. The iterative BOF procedure to locate the volume maximizing initial opening face was not performed at each rotation. Because volume yields were not maximized, it was not possible to determine if a conflict between volume and value maximization existed. The objective of this study was to determine the influence of lumber volume maximization on value yield in sawing hardwood sawlogs.
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Steele, Philip H.; Wagner, Francis G.; Kumar, Lalit; Araman, Philip A. 1993. Influence of Lumber Volume Maximization in Sawing Hardwood Sawlogs. Proceedings of the Forest Industries 21st Wood Technology Clinic Show. pp. 1-26.
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