Transcript Veneer Production Basics A Volume Production

Veneer Production - 2013
Wood Figure
Veneer Production & Usage
Veneers cut from various
stem portions
– (1) crotch
– (2) trunk
– (3) burl
– (4) stump or butt
Process - In the Log Yard
• Logs tagged and tallied
– Calculate volume
– Inventory (tracking number)
– Butts painted
• All logs must be kept wet
– Sprinkler systems
– Protect from drying out & cracking
– Cracks = degrade = lost profit
At the Veneermill:
• Logs debarked
– Debarker or water jet
– Smooth out taper,
remove imbedded rocks
• Logs transferred to saw
– Ripped with band or
circular saw
Pict.: Ring Debarker
At the Sawmill:
• Logs processed
– Faced
– Ripped parallel to or through heart
– Halved or Quartered
• Flitches banded together, heart to heart
The Cooking Vats:
• Banded Logs & Burls cooked in hot water vats
– Soften fiber
– Equalize color variation
• Temperature and schedule
– Species and volume specific
For example: White Oak (Quercus alba)
Cook Time: 72 hours
Water Temp.: 120º C
Flitch & Burl Prep.:
• After cooking….
– Burls pressure washed
Remove mud & rocks
QC inspection
– Logs planed
– QC inspection
Different Veneer Cutting Methods
1) Peeling – Rotary Cutting
2) Rotary Slicing
– Rift cutting
– Half-round slicing
3) Vertical/Horizontal Slicing
– Flat slicing
– Quarter slicing
4) Sawing Method
1) Peeling
Peeling (Rotary Cutting):
– Similar to a giant softwood lathe
– Plywood production, burls, quilts
and figured wood
– Unripped log or burl held between
dogs
– Rotated around central
axis…concentric rotary cutting
Peeling cont.
2) Rotary Slicing
• Another type of rotary cutting...
– Eccentric (elliptical) rotary cutting
– Called “rotary slicing”
– Flitches are mounted on log beam
– Elliptical rotation can be varied/adjusted
– Produces extreme variation in grain
Rotary Slicing cont.
Flat grain
(Flat slicing)
Vertical grain
(Rift cutting)
Flat grain
3) Vertical Slicing
Slicing (vertical):
– Flitch clamped on
movable platen
– Held in place with
dogs
– Pressure bar and knife
fixed, perpendicular
to platen stroke
– Slicing done in up or
down stroke
Quarter Slicing
Quarter Slicing
Flat Slicing
Flat Slicing
Horizontal Slicing
• Slicing (horizontal):
– Flitch placed on fixed platen
– Held in place with stays or dogs
– Pressure bar and knife move over flitch
– Knife and bar skewed….shear veneer from wood
Horizontal Slicing Method
Flat grain
Vertical grain
4) Veneer Sawing:
– Veneer cut from cants
– Employs a veneer re-saw, similar to band
saw
– Not usually used in high production
environments
– Low yield, but usually very high quality
slices
Conditioning & Drying:
• Once cut, moisture must be removed from the
veneer
– Done to avoid warp, checks, color change and
bacterial attack
– Process is dependent on species
– Final moisture content specified by customer
Conditioning & Drying:
• Conditioning (Natural or Slow Drying):
– Veneer is placed in environmentally controlled
rooms
– Individually shelved
– Lengthy drying periods
– Very gentle to veneer
– Results in high yield and quality
Conditioning & Drying:
For example:
Walnut burl requires 24 hour “breathing” before
drying
If not, veneer turns green in the dryer!
Conditioning & Drying:
• Drying (Synthetic or Forced Drying):
– Veneer is feed through dryer on a metal screen
conveyor
– Dried under pressure and forced air
– Operator can vary feed rate and final moisture
content
– Dryer is divided into three distinct sections:
Conditioning
Drying
Cooling
Conditioning & Drying:
• Synthetic or Forced Drying:
– Conditioning
Initial moisture removed by high velocity air (90º
to 120ºC)
Screens “hold” veneer...only contact pressure
– Drying
Veneer heated with high velocity & temperature
air (110º to 130º C)
Screen press veneer flat to keep from warping
Conditioning & Drying:
• Synthetic or Forced Drying:
– Cooling
Veneer cooled with ambient high velocity air
Screen pressure maintained
At out-feed...veneer piled in packs of 16, 24 or 32
Trimming & Packaging:
• Piled veneer is trimmed in packs
– Usually done with a large guillotine slicer
– Packs trimmed “true”
– Bundled & tagged
Trimming & Packaging:
• Operator grades untrimmed packs
– Assesses best trim and highest yield
– Must be informed of grade rules
– Grade rules depend on customer
Trimming & Packaging:
• Once trimmed, packs bundled & banded
– Packs inventoried according to log tracking number
Storage & Transportation:
• Shipping
– Shipped packs shrink wrapped and banded on skids
(pallets)
– In some cases, packs banded between porous woods
(poplar) to draw moisture away
• Packs usually shipped in sealed containers to
ensure dry environment