Lumber Drying Reasons to dry lumber --Dimensional stability Methods --Dry wood is stronger than wet wood --Dry wood is more durable against decay and insect damages Methods --Air drying with natural elements (temperature, humidity, wind) Moisture Content ≤ 19% --Kiln drying: drying under controlled environments Moisture Content ≤ 15%

Drying Procedures Sorting for Grades, thickness, species, sometimes MC based on drying rates Stacking & stickering Good stacking & stickering ensures a successful drying operation Air-drying

Bad Stacking & Stickering

Kiln Drying Basic Elements --A compartment to enclose lumber --Heating (coils) --Vents and steaming device to regulate relative humidity --Fans for air circulation

Planing Lumber is knife planed Where F = feed speed Basics of planing Planing is done by passing lumber through a series of planer cutterheads. Surface qaulity is defined by length of knife marks (Ft) and depth of knife marks (h). Ft = 12 x F NT Where F = feed speed N = Revolutions per minute T = Number of knifes on cutterhead Lumber is knife planed

Planing Operation

Sanding (Machining with coated abrasives) Basics Wood-based composite panels are finished with coated abrasive, which consists of backing, resin sizing and minerals (abrasives). Abrasives --Garnet (Hardness 7.5) --Aluminum oxide (9.5) --Silicon carbide (9.6, diamond 10) Grit size The higher the number the finer is the grits, 60, 80, 100,……

Lumber Grades and Grading Hardwood Lumber Grades: Hardwood lumber is graded according to size and appearance

Softwood Lumber grades Softwood lumber is graded for strength

Methods of Grading Softwood Lumber Visual Grading: Examining each piece for strength- reducing defects and assign a strength ratio (% strength remained) relative to a piece without any defect. Machine Grading: Flexing each piece to an extent not to cause any damages, followed by calculating MOE (modulus of elasticity) and estimating MOR (modulus of rupture). Grading also can be done with ultrasound Method. Both methods are non-destructive evaluation (NDE) .