Handling rates and costs associated with using short-length lumber (less than 8 ft. long) in furniture and cabinet industry rough mills have been assumed to be prohibitive. Discrete-event systems simulation models of both a crosscut-first and gang-rip-first rough mill were built to measure the effect of lumber length on equipment utilization and the volume and value of the rough parts produced. In the crosscut-first mill model, the volume and value of parts produced from short-length lumber compared favorably with the volume and value of parts produced from the medium- (8 to 13 ft. long) and long- (14 to 16 ft. long) length lumber. A «conservative case» short-lumber scenario was also simulated in which the distribution of cutting lengths was varied. The short-lumber volume and value yields for this model version were somewhat lower than the medium- and long-lumber yields. In the gang-rip-first mill model, the volume and value of parts produced from short lumber were equal to approximately 60 percent of the production from the medium and long lumber. The unstacker and planer were unable to provide sufficient material to the ripsaws which, in turn, were unable to process the short lumber fast enough to keep the chop saws busy
In recent years, producers of solid wood dimension parts have emphasized improvements in lumber yield, focusing primarily on lumber grade and cutting technology rather than cutting bill design. Yet, cutting bills have a significant impact on yield. Using rip-first rough mill simulation software, a data bank of red oak lumber samples, and a cutting bill that resembles those used in industry, we determined the effect of changes in part size within an existing cutting bill and the impact of part-quantity requirements on yield. The results indicated that cutting bill requirements have a large influence on yield when the shortest part length in the bill is changed. Medium-length part sizes also affect yield except when the cutting bill requires an unlimited number of small parts; in this case, yield always will be high. When an all-blades-movable arbor is used, length changes in the bill affect yield more than changes in width. This study reveals our current lack of understanding of the complex relationship between cutting bill and lumber yield, and points out the yield gains that are possible when properly designed cutting bills are used.
ABSTRACT.—This study examined the effects that silvicultural treatments have on the tree grade distribution of a mixed hardwood stand located on the Vinton Furnace Experimental Forest. Four stand treatments were established: a commercial clearcut, a commercial clearcut with timber stand improvement (TSI), a selection cut, and a selection cut with TSI. Trees were found to be of better quality in the selection cuts, where the odds of a tree being classified into the same reference grade or higher grade vs. lower than the reference grade were found to be 1.5 to 12.3 times the odds of a tree in the commercial clearcut being classified into the same reference grade or higher grade vs. lower than the reference grade. As a group, stands where TSI was applied had different odds for better quality trees than did stands without application of TSI. Within the commercial clearcut treatments, TSI had a significant positive effect on tree grade odds, but TSI did not prove beneficial within the selection cuts. Past potential tree grade measurements were also examined to determine their effectiveness in predicting future grade. It was found that between one-half to twothirds of the trees in this study had the same potential tree grade in 2000 as they did in 1989.
Automated lumber grading and yield optimization using computer controlled saws will be plausible for hardwoods if and when lumber scanning systems can reliably identify all defects by type. Eisting computer programs could then be used to grade the lumber, identify the best cut-up solution, and control the sawing machines. The potential value of a scanning grading system depends on the accuracy and reliability of the computer-assigned grades compared to the performance of human graders. The potential worth of any scanning cut-up system is largely dependent on the parts recovered compared to today’s standard rough mill processing systems. The Center for Automated Processing of Hardwoods' (CAPH) scanning system tested is a color line-scan camera-based image processing system. We compared the system’s scanning-grader performance with the NHLA (National Hardwood Lumber Association) grades assigned by company graders. The scanning-grader results indicated that 20 of 50 company graded boards were graded too high and 5 too low. In total , 50 percent of the boards were manually misgraded. Initial results indicate that the CAPH color camera system missed small sections of some defects and misclassifyed some clear wood as defective.
The lumber processed in most rough mills typically arrives in packages of random-width boards with lengths ranging from 8 to 16 feet; however, little information is available on how board widths affect rough mill yield given varying part-prioritization strategies and cutting bills. The objective of this study was to determine the impact on yield obtained by processing the same volume of lumber and grade mix from narrow boards (4 in. ≤ x < in.), medium-width boards (6 in. ≤ x < 8 in.), and wide boards (8 in. ≤ x < 10 in.). Rip-first simulation software (ROMI-RIP 2.0) was used to compare yields for easy and hard industry cutting bills. Three prioritization strategies (L 2 × W, L 2 × W × N, and CDE) were used to compare current practices with the complex dynamic exponent (CDE) optimal strategy. Total yield, for the Easy cutting bill, was similar for all width-groups; however, when processing the Hard industry cutting bill, the wide boards had significantly higher yields (by at least 1.3% using CDE). For the CDE prioritization strategy, primary yield was significantly higher for narrow boards compared to the wide boards when using the Easy cutting bill (by more than 1.2%); however, when processing the Hard cutting bill, the wider boards had a significantly higher primary yield of at least 2.6 percent. Wide boards had a significantly higher salvage yield by at least 1.7 percent with the Easy cutting bill. The Hard cutting bill salvage yield was at least 1.2 percent higher when processing the medium-width boards. Grading rules and part size distribution were factors for this outcome. Smaller boards required more clear wood in order to meet the cutting units requirement for grade. Short/narrow boards had fewer surface defects than large/wide ones, which, in turn, affected yield.
The 1992 Data Bank for Red Oak Lumber is a collection of fully described FAS, Selects, No. 1 Common, and No. 2A Common boards (a total of 1,578 at present). The data bank has two unique features to aid in sample selection. The first feature is the double grading of FAS, No. 1 Common, and No. 2A Common boards to reflect the surface area in grading cuttings when grading with standard National Hardwood Lumber Association (NHLA) procedures and when using as many grading cuttings as possible under NHLA rules. The latter gives a more accurate predictor of the potential utility of the board. The second feature is the inclusion of quality levels for the No. 1 Common and No. 2A Common boards. Written for researchers and industrial decision makers who may have only a limited knowledge of the NHLA grades, the data bank contains a limited description of factors affecting the grades. Included are a description of Realistic Grading System (ReGS), the computer program for grading lumber; some reasons why lumber users who buy kiln dried lumber may want to specify the Special Kiln Dried Rule; the effect of kiln-drying on soundness of knots; and the surprising finding that relatively few No. 1 Common and No. 2A Common boards contain any pith at all.
Wounding from prescribed fires and forest harvest operations creates concerns about the future health, grade, volume, and value recovery potential of affected trees. The wounds, regardless of origin, may compartmentalize and heal over. Or they may be slower to heal or too significant to defend against pathogens that invade the wound zone and promote decay formation and spread. Even tree species that are good at compartmentalization after being wounded can succumb after a series of wounding events. We often create this scenario when conducting prescribed fires in conjunction with thinning and regeneration operations. A combination prescribed fire–shelterwood treatment study to evaluate oak regeneration (Quercus spp.) and establishment in a mesic mixed-oak forest was conducted in 2000 in West Virginia. Before and after each of two prescribed fires that were intended to eliminate a shade-tolerant understory, a shelterwood harvest to open the canopy to promote oak regeneration, and a subsequent prescribed fire designed to further cull less fire tolerant non-oak species, tree-quality conditions were evaluated for all stems 5-inch diameter at breast height and larger. The initiation and development of wounds and broken tops were tracked and correlated with silvicultural activities and weather events. The cumulative and interaction effects of repeated mechanical stressors on these stems are significant factors in long-term research that seeks to determine the costs and benefits of prescribed fire treatments to promote oak regeneration.
No standard definition for production exists today, especially specific to the wood products industries. From a management point of view, even the more straightforward management issues surrounding the concept of lean are complex. This exploratory research seeks to develop a methodology for quantitative and objective assessment of the leanness of any wood products operation. Factor analysis is a statistical approach that describes the patterns of relationships among quantifiable predictor variables, with the goal of identifying variables that cannot be directly measured, such as the leanness of a company. Using this technique, a factor model was identified and a factor score, or Index, was developed. For the nine wood products companies included in this study, the average Lean Index is demonstrated to be 5.07, ranging from a low of 2.33 to a high of 12.00. Based on the quantified standards of production developed in this study, (1) primary wood products operations are inherently leaner than secondary wood products operations; (2) process throughput variables explain approximately twice the total variance of all consumed resources, compared to process support variables; and (3) energy consumption is shown to be the single most significant contributor to the leanness of any wood products company.
