Lumber Manufacturing---Debarking

• Purpose—Increase value of byproductsPurpose—Increase value of byproducts ----Scrapes and edgingsScrapes and edgings → → chips without barkchips without bark → → pulppulp

--Bark particles --Bark particles → → burn (energy)burn (energy)

• Types of debarkersTypes of debarkers --Drum debarker: removing bark from pulp logs--Drum debarker: removing bark from pulp logs

--Ring debarker: removing bark from saw- and veneer logs--Ring debarker: removing bark from saw- and veneer logs

--Pole shaver: shave bark off utility poles--Pole shaver: shave bark off utility poles

Drum DebarkerDrum Debarker

• To remove bark from pulp logsTo remove bark from pulp logs

Corrugated interior tumbles the logs and scrapes off bark;Corrugated interior tumbles the logs and scrapes off bark;

logs rub against each other to knock off bark; water showerlogs rub against each other to knock off bark; water shower

softens bark and washes bark out of the drum. Because ofsoftens bark and washes bark out of the drum. Because of

gentle rubbing actiongentle rubbing actionvery little removal of very little removal of quality fibers from surfaces.quality fibers from surfaces.

Ring Debarker

• To remove bark from saw- and veneer-logsTo remove bark from saw- and veneer-logs

Logs are centered in a ring of rosser Logs are centered in a ring of rosser heads with projecting teeth; bark isheads with projecting teeth; bark isremoved with a pressure about 30 toremoved with a pressure about 30 to50 psi. Bark is removed at high speed50 psi. Bark is removed at high speedwith substantial surface removal ofwith substantial surface removal ofwood but does not affect lumber orwood but does not affect lumber orveneer yield.veneer yield.

Pole ShaverPole Shaver

• To move bark from utility poles to obtain smooth surfacesTo move bark from utility poles to obtain smooth surfaces

Pole rotates as it passes under a floatingperipheral-milling cutterhead, removingthe bark with a minimum of wood lossand retaining the natural taper.

Primary Breakdown—Head saws

• Band saw: Able to handle large logs,Band saw: Able to handle large logs, provide straight cuts and thin saw kerfprovide straight cuts and thin saw kerf increase lumber yield.increase lumber yield.

• Circular saw: Saw diameter limits log sizes,Circular saw: Saw diameter limits log sizes, thick saw blades for stability (1/4”)thick saw blades for stability (1/4”)

large saw kerfslarge saw kerfs reduces lumber yield.reduces lumber yield.

Saw MillsSaw Mills

• Scragg MillsScragg Mills Consists two or four circular saws on a common arbor. DistanceConsists two or four circular saws on a common arbor. Distance

between blades can be adjusted to produce 4-, 6-, or 8-inch cants.between blades can be adjusted to produce 4-, 6-, or 8-inch cants. The logs are commonly moved through saws by a conveyor.The logs are commonly moved through saws by a conveyor.

• Multiple Band MillsMultiple Band Mills Similar to scragg mills except that breakdown is done by 2 or moreSimilar to scragg mills except that breakdown is done by 2 or more opposing bandsaws, producing two slabs and one cant if two bandsopposing bandsaws, producing two slabs and one cant if two bands are used.are used.

• Chipping HeadrigsChipping Headrigs Logs pass through a set of side cutterheads to remove excessLogs pass through a set of side cutterheads to remove excess

wood into chips, followed by another set of top/bottom cutter-wood into chips, followed by another set of top/bottom cutter- heads to produce a cant. Chips are to be used for pulp & paper.heads to produce a cant. Chips are to be used for pulp & paper.

Chip-N-Saw

Designed to process small straight Designed to process small straight Logs 6 to 16 inches in diameters.Logs 6 to 16 inches in diameters.Logs first pass through two pairs Logs first pass through two pairs side and top/bottom) chipping side and top/bottom) chipping cutterheads to square or shapecutterheads to square or shapelogs, followed by passing the cantlogs, followed by passing the cantthrough a series of circular saws through a series of circular saws mounted on a common arbor to mounted on a common arbor to produce multiple pieces lumber.produce multiple pieces lumber.

High-Tech MillsHigh-Tech Mills

• BOF (Best Opening Face)BOF (Best Opening Face)

For high efficiency: Electronic hardware (scanner & computer) and good computerFor high efficiency: Electronic hardware (scanner & computer) and good computersoftware; machine that is able to position logs quickly & saw accurately with thin kerf.software; machine that is able to position logs quickly & saw accurately with thin kerf.

ResawingResawing

• Ripping—Ripping—Ripping is to saw lumber along the grain. Slabs Ripping is to saw lumber along the grain. Slabs produced by headrigs are cut with a pair of circular saws (called produced by headrigs are cut with a pair of circular saws (called an edger) to square the edges to a specific width simultaneously. an edger) to square the edges to a specific width simultaneously. Large slabs are rip into multiple pieces with a series of circularLarge slabs are rip into multiple pieces with a series of circularsaws mounted on a common arbor (gang saws).saws mounted on a common arbor (gang saws).

• Rough trimming—Rough trimming—Trimming is to saw lumber across the Trimming is to saw lumber across the

grain to a specific length. Rough trimming follows the rippinggrain to a specific length. Rough trimming follows the ripping

to cut green lumber into pre-determined lengths, usually done to cut green lumber into pre-determined lengths, usually done with a pair of hollow ground circular saws.with a pair of hollow ground circular saws.

Sorting & Drying

• Sorting—Sorting—This operation is to sort cut lumber into differentThis operation is to sort cut lumber into different

grades, species or species groups, thickness, length andgrades, species or species groups, thickness, length and

sometimes according to moisture content.sometimes according to moisture content.

• Drying (seasoning)Drying (seasoning)

--Reasons to dry : Seasoned wood is dimensionally stable--Reasons to dry : Seasoned wood is dimensionally stable

Dry wood is durable against inscets & Dry wood is durable against inscets & decaydecay

Dry is strongerDry is stronger

--Air-dried lumber: moisture content >15% ≤19%--Air-dried lumber: moisture content >15% ≤19%

--Kiln-dried lumber: moisture content ≤15%--Kiln-dried lumber: moisture content ≤15%