37
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
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
Circular saw
2
4
Waste Factor Comparison
Band Saw Circular saw
Log yard
Side boards
Bucking
DebarkerHeadrig
Gang Saw
Trimmer
Edger
Cants
Sawmill – generic overview
Sorter, Stacker
6
Gang Sawing
gang saw blades
cant
Gang saws
• Fixed, oscillating blades
• Little flexibility
• Intermediate kerf
• Single pass
• High throughput
7
Gang saws
8
9
Log breakdown patterns
1. live sawing 2. cant sawing 3. sawing for grade 4 & 5. sawing for edge grain 6. dimension lumber
10
11
Optimization software
12
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
16
#2
2x4
16
#2
Sawmill optimization
13
(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
16
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
17
18
7. Lumber Grading - Trimming
19
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
20
21
Trimming
• The trim saw is used to cut the boards to length
Lumber is trimmed to lengths of 2 foot multiples.Uses circular saws.
22
Trimming
Multi-saw trimmer
23
Log yard
Side boards
Bucking
DebarkerHeadrig
Gang Saw
Trimmer
Edger
Cants
Sawmill – generic overview
Sorter, Stacker
The “Green Chain”
25
Descrambler
26
27
J-bar sorting
• The lumber is scanned and sorted into bins depending on– species, grade, dimensions
Multiple sort bins
28
29
Stacking
30
Drying kilns
Reasons for drying lumber
• Increase strength of lumber
• Reduces later dimensional changes
• Increases decay/insect resistance
• Decreases weight of lumber
31
Drying
• Drying factors– Temperature– Relative humidity– Air circulation
32
LumberSticker
33
Planermill
SawmillLogyard
Kilns
Planermill
34
Planer
35
Planer
36
Planer
4 knifes per planer head 24 knifes per planer head
37
Waste Management• Trim ends• Chips• Sawdust• Planer shavings• Bark• Hog fuel
