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?