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Plywood is panel product of peeled veneer layers glued together so that the grain direction
of some wood veneers run perpendicular to and others parallel to the long axis of the panel
Plywood also claims a high versatility of end uses. Its relatively simple to manufacture and
has many advantages over other wood converted products as well as some steel and
sheet metal applications
Uneven number of veneer is often used (e.g. 3, 5, 7) *a symmetry makes the board less
prone to warping.
Two outer veneers are called the face and back veneers and the middle veneer called the
1. Interior Plywood
The interior plywood is used for construction that is carried out inside
a house. These plywood are not meant for external use, as they
cannot stand excess moisture.
2. Exterior Plywood
The exterior plywood is glued together with a gluing material that can
withstand moisture. Thus, it is used for constructions carried out
outdoors or areas of little moisture.
3. Structural Plywood
These are extra strong plywood's that are glued together with an
adhesive that holds the layers firmly. The structural plywood can be
used for internal or external purposes. These are basically not meant
to be seen and are mostly hidden behind other constructions.
4. Marine Plywood
The marine plywood is fabricated with a superior glue that is bonded
tightly and resistant to water. It is the strongest, toughest and highest
UP AND GLUE
Timber in log form - In general criteria
relates to log size, quality and grades, log
transport and handling requirements, and
log protection and quarantine
The purpose of this operation is to remove the
outer bark of the tree without substantially
damaging the wood
After the bark is removed, the logs are cut to
appropriate lengths in a step known as bucking
The logs (now referred to as blocks) then are heated to improve the cutting
action of the veneer lathe or slicer - thereby generating a product from the
lathe or slicer with better surface finish
Blocks are heated to around 93°C (200°F) using a variety of methods--hot
water baths, steam heat, hot water spray, or a combination of the three
The veneer log is temporally softened making it more plastic, pliable
and more readily peeled and the quality and quantity of veneer
recovered from heated logs is greater.
After heating, the logs are processed to
There are two method to produce veneer
2. Peeling (Rotary cutting)
Slicing produce more decorative veneer than
Decorative hardwood veneers are usually
sliced much thinner than 3 mm (1/8 in.) thick.
Veneers are taken from the clipper to a veneer dryer where
they are dried to moisture contents that range from around 1
to 15 percent.
Target moisture content depends on the type of resin used
in subsequent gluing steps. The typical drying temperature
ranges from 150° to 200°C (300° to 400°F)
Type of veneer drying are:
1. Jet Dryer
3. High Temperatures Preheaters
Assembly of the plywood panels must be
symmetrical on either side of a neutral center
in order to avoid excessive warping.
Resin is spread on two sides of one ply of
veneer, which is then placed between two
plies of veneer that are not coated with resin
Type of glue spreading
1. Roller glue spreader
2. Spray coaters
The laid-up assembly of veneers then is sent
to a hot press in which it is consolidated
under heat and pressure
There are two type of veneer pressing
2. Hot pressing
Typical press temperatures range from 132°
to 165°C (270° to 330°F) for softwood
plywood, and 107° to 135°C (225° to 275°F)
for hardwood plywood.
The plywood then is taken to a finishing
process where edges are trimmed
Besides, the plywood will be cut into the size
The face and back may or may not be
The type of finishing depends on the end
1. High uniform strength
2. Availability of relatively large sizes
3. Economical and effective utilization of figured wood
4. Freedom from shrinking, swelling and warping
5. Non-splitting qualities solid wood splits fairly readily along the grain.
6. Ease of fabrication of curved surfaces
7. The conservation of timber by the elimination of the waste which occurs in
sawing (e.g. sawdust)
1. The layering effect in plywood makes it porous and susceptible to water
damage if exposed over time.
2. Plywood becomes heavy when wet and should be covered if left outside to
reduce the risk of water damage.
3. Plywood has lots of splinters on the edge after cutting.
4. Edges of board are unattractive and can't be covered
5. Not suitable for many joints
6. Still may contain natural defects such as knots due to the sheets of veneer