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Lumber Production

Lumber Production

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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