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Lumber Production

FW1035 Lecture 12 Bowyer et al, Chapter 13. Lumber Production. Sawmill Goals. Maximize the value and yield of the primary final product (lumber) Maximize value and yield of secondary products (2006 numbers for softwood mills) Chips – 95% pulp Sawdust and planer shavings

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Lumber Production

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  1. FW1035 Lecture 12 Bowyer et al, Chapter 13 Lumber Production

  2. Sawmill Goals • Maximize the value and yield of the primary final product (lumber) • Maximize value and yield of secondary products (2006 numbers for softwood mills) • Chips – 95% pulp • Sawdust and planer shavings • 59% - composite boards (e.g. particleboard, MDF) • 25% - fuel • 7% - animal bedding • 4% - pellets • Bark for horticultural mulch and fuel

  3. Maximizing the total value of products from a log. Softwood Mills – large, highly automated, commodity-oriented Hardwood Mills – Smaller, labor-intensive, specialty-oriented

  4. Today’s Mills • Changing resource forced efficiency improvements • Trend to smaller mills, more evenly distributed through resource area • Closing of old mills; opening of new mills as resource availability changes • Scanners and computer control are important steps now, especially in softwood mills • High level of automation • Reduced labor costs • Waste has been dramatically reduced • Can recover 70% of log volume as lumber from some logs (8-10 inch diameter class) • Much greater emphasis on secondary products

  5. Distribution of Softwood Sawmills in the U.S. and Canada

  6. Softwood and Hardwood Lumber Production Distribution in the U.S. • South (44%) the major producer of lumber (softwoods and hardwoods) • West (36%) - mills produce more per mill, but fewer mills (mainly softwood) • North and northeast - only 20% of US lumber (hardwood and softwood)

  7. Commercial Softwood Lumber Use • Uses (2003) • 38% Residential houses and apartments • 27% Repair and remodeling • 2% Commercial low-rise buildings • 33% Non-residential high-rise, manufacturing/industrial, pallets/crates, misc. • Species • Douglas-fir and southern pine (75%) • Minor (but significant) species: • Western white and sugar pines • Ponderosa pine • Western hemlock • True firs

  8. Commercial Hardwood Production • High grades for furniture, millwork, floors • Largest single use is pallet/crating production • 27% of hardwood lumber • Softwoods also used on west coast • Railroad ties: • 25 million produced annually (60% in the south) • 80% of them from dense hardwoods (oak, maple, hickory)

  9. Most Harvested: Red oak (single most important species group) White oak The gums Yellow poplar Maples Ashes Furniture Use: Red oak Black walnut Black cherry Hard maple Yellow birch Then the others (ash, gum, elm, yellow poplar) Hardwood Species

  10. Terminology Based on Thickness and Size Softwoods (Nominal Dimensions): • Boards – 2 inch thickness or less • Dimension – >2 to 5 inches • Timbers – 5 inches or greater Hardwoods: • “Dimension” - stock sizes for furniture or pallet manufacturing • “Parts” – specific sizes needed for a particular furniture, millwork, window, etc. part

  11. Dimension Lumber Nominal vs Actual Lumber Dimensions

  12. Other Terminology Rough-Sawn Lumber – Unplaned/surfaced, non-kiln dried lumber, usually full nominal dimensions S4S – Surfaced (sanded) on four sides “Quarter” Thickness System - For rough-sawn lumber, thickness given in quarters of an inch. E.g. 4/4 = four quarter or one inch thick. Others: 5/4, 8/4, 10/4 etc. Board Foot - Rough sawn lumber is usually sold by the "board foot" (bd. ft.). A board foot is equal to a piece of wood 12 inches long x 12 inches wide and 1 inch thick, or 144 cubic inches.

  13. The Sawmill Process • Debarking • Primary breakdown • (Secondary breakdown) • Edging and trimming • Sorting to size • Drying • Planing • Grading and re-sorting

  14. Debarking Removes bark and dirt from the logs before they enter the process • Helps to limit saw dulling • Adds value to chips and slabs • Bark can be used as fuel, mulch, etc • Enhances accuracy of shape scanning

  15. Types of Debarkers • Water jet (uncommon) • Drum • Ring • Rosserhead High pressure water jet Drum debarker

  16. Ring Debarkers

  17. Rosserhead Debarkers

  18. Primary Breakdown – “Headrigs” Two Basic Types: • Carriage Headrig • more common with hardwoods • also large, high value softwoods • time here is expensive - move to secondary breakdown • Single Pass Headrig • automated process • softwood dimensional lumber • plywood veneer bolt cores

  19. Band Saw Carriage Headrig

  20. Circular Saw Carriage Headrig

  21. Single Pass Headrig - The ‘Chip-n-Saw’

  22. Example of production from a “Gang Saw”

  23. Secondary Breakdown and Optimization • Re-sawing of boards coming off the headrig • Cants from carriage cut into boards with a gangsaw • Two types: • circular saws • band saws • Optimization maximizes value yield

  24. Computer Controlled Optimization

  25. Sorting, Drying, and Surfacing • Initial sorting into thickness and width classes • Drying (kiln, air, or combination of both) • Surfacing in a planer mill • machined to final dimensions • Grading • Resorted for grade, species, and dimensions

  26. Sorting line at Sawyer red pine sawmill near Gwinn

  27. Typical Lumber Drying Kiln

  28. Drying Lumber • Hardwoods – no standard %MC • Range: 6-10% • Frequently specified by customer • Softwoods • Green – wood was above 19% MC when surfaced (air dried) • Dry or KD 19 – surfaced when wood was <19%MC • KD 15 or MC 15 – surfaced when wood was 15%MC or less

  29. Surfacing • Stamped on boards • Type of surfacing is based on intended use and customer preference • S2S • S4S • Surfacing can be done green or dry • S-Green • S-Dry

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