lecture 16 plywood bowyer, ch. 14 usesclassroom.kleinisd.net/users/2411/lecture 16 - plywood.pdf ·...
TRANSCRIPT
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• Softwood plywood • Structural • Similar to OSB • Sheathing, subflooring,
concrete forms, etc.
• Hardwood plywood • Typically decorative • Furniture, flooring,
cabinetry, etc.
Lecture 16 Plywood
Uses: Bowyer, Ch. 14
Veneer – A thin layer or sheet of wood.
Plywood is pretty strong stuff: http://www.maniacworld.com/Motivational-Speaker-Fail.html
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• Douglas-fir and SYP dominate U.S market • Plywood is classified by veneer grade and/or
application. E.g.: • sheathing • siding • concrete form • marine use
• Grades are based on quality of face and back veneers, adhesive used, thickness, etc.
• Low density hardwoods (aspen, cottonwood, gums, and poplar) may be used as core material.
Structural Plywood
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Hoop Pine Plywood Manufacture
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Typical Manufacturing Steps • Cut blocks to length and debarked • Hydration and heating - particularly important in the
winter • Softens the wood • Typically soaking, may also be done by steaming or
spraying with hot water
• Peeling - rotary cut or sliced • Clipping of veneer
• “ribbon” of rotary veneer cut to 54 inch lengths • sliced veneer - edges are squared
• Veneer drying - impingement (jet) dryers • Adhesive coating and lay up • Pressing - heat cures the glue (low pressure process) • Trim to 4x8, sanded, packaged, and shipped
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Veneer Cutting Slicing (decorative applications)
Peeling (structural and decorative)
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Sliced Veneer
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Veneer Handling and Drying
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Adhesive Coating and Lay-Up
• Veneer layers are symmetrical to center plane • Often oriented at 90° angles
to each other • Lower quality veneers in
core • Faces may be different
species for decorative plywood
• “Balanced Construction” • Adhesive is either
automatically or manually applied to alternate veneers.
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Pressing
• High temperature, multi-opening press
• Loose assembly becomes a panel
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Veneer Grades
“Natural Finish” is the highest grade of veneer. Essentially no defects or patches.
12 Examples of Veneer Patches. Also called “plugs”.
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32/16 – 32 inch span for roof sheathing / 16 inch for subflooring
Exposure 1 – Manufactured with waterproof adhesive
Exposure 2 - (Interior) adhesive is only water resistant
Exposure 3 – (Interior) non-water resistant adhesive
This grade is also called CDX – C and D face veneers with exposure 1 adhesive.