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
Waste Factor Comparison Band Saw Circular saw
Sawmill – generic overview Log yard Bucking Headrig Debarker Cants Side boards Gang Saw Trimmer Edger Sorter, Stacker
Gang Sawing cant gang saw blades
Gang saws Fixed, oscillating blades Little flexibility Intermediate kerf Single pass High throughput
Gang saws
Log breakdown patterns 1. live sawing 2. cant sawing 3. sawing for grade 4 & 5. sawing for edge grain 6. dimension lumber
Optimization software
Scanning of the log to optimize the yield Bottom profile Mid-length profile Top profile Product mix selected
Sawmill optimization (Halco Software Systems)
Sawmill – generic overview Log yard Bucking Headrig Debarker Cants Side boards Gang Saw Trimmer Edger Sorter, Stacker
Wane http://www.wdscapps.caf.wvu.edu/lumberrtk/ http://www.decks.com/article197.aspx
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
Sawmill – generic overview Log yard Bucking Headrig Debarker Cants Side boards Gang Saw Trimmer Edger Sorter, Stacker
7. Lumber Grading - Trimming
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
Trimming The trim saw is used to cut the boards to length Lumber is trimmed to lengths of 2 foot multiples. Uses circular saws.
Trimming
Multi-saw trimmer
Sawmill – generic overview Log yard Bucking Headrig Debarker Cants Side boards Gang Saw Trimmer Edger Sorter, Stacker
The “Green Chain”
Descrambler
J-bar sorting The lumber is scanned and sorted into bins depending on species, grade, dimensions
Multiple sort bins
Stacking
Drying kilns
Reasons for drying lumber Increase strength of lumber Reduces later dimensional changes Increases decay/insect resistance Decreases weight of lumber
Drying Drying factors Temperature Relative humidity Air circulation Sticker Lumber Drying factors Temperature Relative humidity Air circulation
Planermill Planermill Kilns Sawmill Logyard
Planer
Planer
Planer 4 knifes per planer head 24 knifes per planer head
Waste Management Trim ends Chips Sawdust Planer shavings Bark Hog fuel