circular saw

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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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Circular saw video

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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