download Plywood

of 24

  • date post

  • Category


  • view

  • download


Embed Size (px)

Transcript of Plywood


2. 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 core veneer 3. 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 grade plywood. 4. LOG STORAGE LOG DEBARKING AND BUCKING LOG HEATING (STEAMING AND SOAKING) VENEER DRYING VENEER CUTTING VENEER LAY UP AND GLUE SPREADING PLYWOOD PRESSING PLYWOOD CUTTING PLYWOOD FINISHING FINISHED PRODUCT 5. Timber in log form - In general criteria relates to log size, quality and grades, log transport and handling requirements, and log protection and quarantine 6. 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 7. 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 93C (200F) 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. 8. After heating, the logs are processed to generate veneer There are two method to produce veneer 1. Slicing 2. Peeling (Rotary cutting) Slicing produce more decorative veneer than peeling method. Decorative hardwood veneers are usually sliced much thinner than 3 mm (1/8 in.) thick. 9. 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 200C (300 to 400F) Type of veneer drying are: 1. Jet Dryer 2. Microwave 3. High Temperatures Preheaters 4. Ultra-Violet 5. Infra-red 10. 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 11. 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 1. Pre-pressing 2. Hot pressing Typical press temperatures range from 132 to 165C (270 to 330F) for softwood plywood, and 107 to 135C (225 to 275F) for hardwood plywood. 12. The plywood then is taken to a finishing process where edges are trimmed Besides, the plywood will be cut into the size needed 13. The face and back may or may not be sanded smooth The type of finishing depends on the end product desired 14. 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) 15. 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 16. Cabinet interiors and exteriors Desk and Table tops Kitchen tops Doors Drawers Furniture Shelves Wall Paneling Interior panels External cladding Plywood sheets flooring Bracing (shearwalls) 17. THANK YOU..