15 manufactured boards
TRANSCRIPT
WOOD MATERIALS TECHNOLOGY
4th Edition
Chapter 15Manufactured boards:
A replacement for solid timber.
Manufacture boardsMan 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
Manufactured boards
Making boards and sheets from wood or wood products– Veneers– Sawdust– Wood fibres– Wood strips– Wood flakes
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
Plywood
Rotary cutting of the veneer
Make-up of plywood– Veneers at 90° to each other– Odd number of layers (5/7)
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
Types of plywood
WBP– Water and Boil Proof– Exterior grade
Marine plywood– Boat building – Exposed situations, roofs
Blockboard
Strips of softwood glued together and faced with veneers
Does not split easilyCan screw into the edgeWide sheets (8’ X 4’)
BlockboardsAdvantage
– 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
Pineboard/lamwood
Made from thin softwood strips, glued together
Makes a wide board in softwood
Uniform thickness (12 – 25mm)Boards tend to cupUseful for projectsHardwood examples can be
obtained
Oriented Strand board - OSBLooks 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
OSB – oriented strand board
Chipboard Made by mixing
wood chips and glueThis mixture is then
pressed and pressed to form a sheet
Plastic or veneer is then placed over it
Used in furniture construction
ChipboardWood chips are glued Pressed into sheetsOften faced with wood veneer
or plastic laminateEdges of the board need to be
covered
Edges
• Edges of chipboard should be covered
Chipboard + OSBAdvantages
– 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
MDF (Medium density fibreboard)
Very popular board materialOften faced with veneer or
plastic laminateMade with fine wood fibres
in three layersNeed to drill into face
before nails or screws are inserted
Fine dust is harmful
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
MDF Manufacture
MDF Manufacture
Hardboard Hardboard is made up from wood pulpWater is added to the pulpThe mixture is then pressed under high
temperatures and the water is removedSheets are smooth on one side and
textured on the other3-9mm thick
Hardboard
• Available in thin sheets • One face smooth, one
textured• Often faced with plastic
laminate• Back of cabinets, base of
drawers• Only used indoors
Quiz
Name the following manufactured boards
− Pineboard− Chipboard
Three layers of wood are being glued to make plywood. Draw a sketch to show the direction in each layer.
The edges of chipboard look poor. Draw a sketch to show how the edges are covered.
− 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
State some advantages of manufactured boards
Water Boil Proof
What do the letters WBP stand for?