15 manufactured boards

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15 manufactured boards

  1. 1. WOOD MATERIALS TECHNOLOGY 4th Edition
  2. 2. Chapter 15 Manufactured boards: A replacement for solid timber.
  3. 3. Manufacture boards Man made woods or manufactured boards have become important as a substitute for solid wood over the past number of years. The main advantages are – Help conserve tropical forests – They are economic alternative – They come in large sizes with uniform thickness – They are stable
  4. 4. Manufactured boards  Making boards and sheets from wood or wood products – Veneers – Sawdust – Wood fibres – Wood strips – Wood flakes
  5. 5. Plywood Thin strips of wood glued together like a sandwich Glue is positioned between each layer In plywood each layer is positioned at 90º There are always an uneven number of sheets used
  6. 6. Plywood  Rotary cutting of the veneer  Make-up of plywood – Veneers at 90° to each other – Odd number of layers (5/7)
  7. 7. Plywood Advantages – Very strong – Stable does not warp or shrink – Does not split easily when nailed – Smooth uniform finish Disadvantages – Unattractive edge must be covered with a veneer, moulding or a slip of wood
  8. 8. Types of plywood  WBP – Water and Boil Proof – Exterior grade  Marine plywood – Boat building – Exposed situations, roofs
  9. 9. Blockboard  Strips of softwood glued together and faced with veneers  Does not split easily  Can screw into the edge  Wide sheets (8’ X 4’)
  10. 10. Blockboards Advantage – Very strong due to different directions of veneer – Resistance to attack from water, heat, chemical, fungi and insect attack – Comes in large sizes – Blockboard comes in large thickness Disadvantages – Edges need to be covered – Surface can be easily damaged
  11. 11. Pineboard/lamwood  Made from thin softwood strips, glued together  Makes a wide board in softwood  Uniform thickness (12 – 25mm)  Boards tend to cup  Useful for projects  Hardwood examples can be obtained
  12. 12. Oriented Strand board - OSB  Looks similar to chipboard but has similar characteristics to plywood  Wooden strands or flakes from tree log are bonded together under heat and pressure by glue  Strands are aligned in 2 outer layers and an inner core is position at 90º to outer layers giving board strength
  13. 13. OSB – oriented strand board
  14. 14. Chipboard Made by mixing wood chips and glue This mixture is then pressed and pressed to form a sheet Plastic or veneer is then placed over it Used in furniture construction
  15. 15. Chipboard  Wood chips are glued  Pressed into sheets  Often faced with wood veneer or plastic laminate  Edges of the board need to be covered
  16. 16. Edges • Edges of chipboard should be covered
  17. 17. Chipboard + OSB Advantages – Can be veneered – Cheap – Uniform thickness – Makes use of waste wood Disadvantages – Rough surface if not finished with a veneer – Chipboard is weak – Water and moisture make the sheets swell
  18. 18. MDF (Medium density fibreboard)  Very popular board material  Often faced with veneer or plastic laminate  Made with fine wood fibres in three layers  Need to drill into face before nails or screws are inserted  Fine dust is harmful
  19. 19. Medium Density Fibreboard MDF Similar colour to hardboard but it is much stronger Manufactured from fibres mixed with synthetic resin binder No water is used so pressing temperatures are lower than for hardboard Both sides have a smooth finish, or boards can have a veneer
  20. 20. MDF Manufacture
  21. 21. MDF Manufacture
  22. 22. Hardboard Hardboard is made up from wood pulp Water is added to the pulp The mixture is then pressed under high temperatures and the water is removed Sheets are smooth on one side and textured on the other 3-9mm thick
  23. 23. Hardboard • Available in thin sheets • One face smooth, one textured • Often faced with plastic laminate • Back of cabinets, base of drawers • Only used indoors
  24. 24. Quiz
  25. 25.  Name the following manufactured boards − Pineboard − Chipboard
  26. 26.  Three layers of wood are being glued to make plywood. Draw a sketch to show the direction in each layer.
  27. 27.  The edges of chipboard look poor. Draw a sketch to show how the edges are covered.
  28. 28.  State some advantages of manufactured boards − − − − − − − − Large sheet sizes Cover large areas easily Uniform thickness Stable – no shrinkage Do not warp Use woods efficiently Little waste Often veneered over – helps to save the rainforests
  29. 29.  What do the letters WBP stand for? Water Boil Proof

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