Transcript Primary lumber processing

Circular Saw
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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
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Circular saw
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Waste Factor Comparison
Band Saw
Circular saw
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Sawmill – generic overview
Log yard
Bucking
Headrig
Cants
Debarker
Side boards
Gang Saw
Trimmer
Edger
Sorter, Stacker
Gang Sawing
cant
gang saw blades
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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
4 & 5. sawing for edge grain
3. sawing for grade
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
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Sawmill optimization
(Halco Software Systems)
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Sawmill – generic overview
Log yard
Bucking
Headrig
Cants
Debarker
Side boards
Gang Saw
Trimmer
Edger
Sorter, Stacker
Wane
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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
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Edger optimizer
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Sawmill – generic overview
Log yard
Bucking
Headrig
Cants
Debarker
Side boards
Gang Saw
Trimmer
Edger
Sorter, Stacker
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
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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
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Multi-saw trimmer
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Sawmill – generic overview
Log yard
Bucking
Headrig
Cants
Debarker
Side boards
Gang Saw
Trimmer
Edger
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
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Multiple sort bins
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Stacking
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Drying kilns
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Reasons for drying lumber
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Increase strength of lumber
Reduces later dimensional changes
Increases decay/insect resistance
Decreases weight of lumber
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Drying
Lumber
Sticker
• Drying factors
– Temperature
– Relative humidity
– Air circulation
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Planermill
Planermill
Kilns
Sawmill
Logyard
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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
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