1 Circular Saw • Not used as headrig in softwood sawmills • Less throughput than band saw • Blades rigid, saw kerf is 1/4” to 3/8” • Relatively wide saw kerf – high waste factor
Jan 08, 2016
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Circular Saw• Not used as headrig in softwood sawmills• Less throughput than band saw• Blades rigid, saw kerf is 1/4” to 3/8”• Relatively wide saw kerf – high waste factor
Circular saw
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Waste Factor Comparison
Band Saw Circular saw
Log yard
Side boards
Bucking
DebarkerHeadrig
Gang Saw
Trimmer
Edger
Cants
Sawmill – generic overview
Sorter, Stacker
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Gang Sawing
gang saw blades
cant
Gang saws
• Fixed, oscillating blades
• Little flexibility
• Intermediate kerf
• Single pass
• High throughput
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Gang saws
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Log breakdown patterns
1. live sawing 2. cant sawing 3. sawing for grade 4 & 5. sawing for edge grain 6. dimension lumber
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Optimization software
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Scanning of the log to optimize the yield
Bottom profile
Mid-length profile
Top profile
Product mix selected
1x4 14 #2
2x4 16 #2
2x4 16 #2
2x4 16 #2
1x4 16 #2
2x4
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#2
2x4
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#2
Sawmill optimization
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(Halco Software Systems)
Log yard
Side boards
Bucking
DebarkerHeadrig
Gang Saw
Trimmer
Edger
Cants
Sawmill – generic overview
Sorter, Stacker
Wane
http://www.wdscapps.caf.wvu.edu/lumberrtk/http://www.decks.com/article197.aspx
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6. Edger
• The edger will rip the rough sawn board to width and remove the wane and other defects. Uses circular saws.
wane wane
saw cuts
Edger optimizer
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7. Lumber Grading - Trimming
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Lumber Grading
• Different grades systems for hardwoods and softwoods• Different grades depend mainly on
– natural defects• size, number and location of knots• size, location and type of stain or rot• amount of wane
– machine defects • skip• snipe
Lumber Grading
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Trimming
• The trim saw is used to cut the boards to length
Lumber is trimmed to lengths of 2 foot multiples.Uses circular saws.
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Trimming
Multi-saw trimmer
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Log yard
Side boards
Bucking
DebarkerHeadrig
Gang Saw
Trimmer
Edger
Cants
Sawmill – generic overview
Sorter, Stacker
The “Green Chain”
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Descrambler
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J-bar sorting
• The lumber is scanned and sorted into bins depending on– species, grade, dimensions
Multiple sort bins
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Stacking
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Drying kilns
Reasons for drying lumber
• Increase strength of lumber
• Reduces later dimensional changes
• Increases decay/insect resistance
• Decreases weight of lumber
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Drying
• Drying factors– Temperature– Relative humidity– Air circulation
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LumberSticker
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Planermill
SawmillLogyard
Kilns
Planermill
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Planer
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Planer
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Planer
4 knifes per planer head 24 knifes per planer head
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Waste Management• Trim ends• Chips• Sawdust• Planer shavings• Bark• Hog fuel