Effect of visual grading on lumber quality /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Grading southern pine dimension lumber consists of a human grader visually inspecting each piece of lumber and assigning it a grade. It is at this point in the mill process where the value of each individual piece is determined. Southern pine dimension lumber is a commodity product. In theory, the customer bases the purchase on price only. However, some mills produce lumber that is either of higher quality for certain grades than that stated by the Southern Pine Inspection Bureau, the major rules writing agency for southern pine, or they produce a special grade that is customer specific. In this way, the individual producer moves some of this product out of the commodity class. A database of typical southern pine two-by-four lumber was measured in such a way that it could be sorted using all feasible combinations of grading criteria. The reasons for degrade were examined. A computer model was developed that determined the grade for each board in the database. The amount of lumber trim and the final board grade were determined by the highest value, based on user-input lumber and trim prices. Evaluation of the database using special grades was also examined. Volume and value differences between the lumber grade mixes, resulting from using standard grades only, and using standard grades and a special grade, were examined. Knots, wane, and warp (bow, crook, twist) were the major causes of degrade in the lumber. These defects accounted for 82.6% of the boards being graded lower than Select Structural, the highest quality grade in the study. Three special grades were examined. The more restrictive the grade was made, the smaller the difference was in profit when compared to the lumber graded only by SPIB standards. Actually, the price of a special grade would be market determined and the more restrictive special grades would be valued higher than those with less severe restrictions. A simulated lumber database was used to verify LUMGRAFS accuracy. LUMGRAFS was verified to accurately assign defect location and size, board trim and grade, and board value, to a simulated lumber database. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Forestry." |
| Physical Description: | xv, 275 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |