Timbers- DT IGCSE

Define Timber

wood that has come from tree trunks and has been dried and cut into usable planks or boards

Define hardwood

wood that comes from deciduous trees-trees that shed their leaves annually.These trees grow slower than softwood trees, hence making hardwood a denser, stronger and more expensive wood

Types of Hardwoods:

• oak

• mahogany

• birch

• ash

• jelutong

• balsa

• beech

Types of Softwood

• cedar

• pine

• larch 

• fir

Advantages of using Oakwood

Tough, durable and polishes well

Disadvantages of using Oakwood

• expensive

• difficult to work with

• can warp or crack

Uses of Oakwood

Furniture

Advantages of Jelutong

Even,close grain is easy to cut and shape

Disadvantages of jelutong

Soft and not very strong-not good for structural uses

Uses of jelutong

Model making and vacuum forming

Advantages of Birch wood

Regular even grain easy to work

Disadvantages of birch wood

Low resistance to rot and insect attack

Uses of birch wood

Veneers- to make plywood

Advantages of Ash wood

Strong, tough flexible and finishes well

Disadvantages of ashwood

Low resistance to rot and insect attack

Common Uses of Ashwood

Handles for tools, sports equipment

Advantages of Pine(Soft wood)

Very durable
Easy to work
cheap

Disadvantages of Pine(Softwood)

Can warp, crack and splinter more than other woods

Common uses of Pine wood

• house construction

• floorboards

• interior work

Advantages of cedar(Soft wood)

-Natural oils make it resistant to water and fungal growth

Disadvantages of cedar wood(Soft wood)

More expensive than pine and not as strong

Common uses cedar (Softwood)

Outdoor furniture, fences, sheds, boats

Types of Manufactured timbers

• plywood

• MDF

• chipboard

Process on how plywood is manufactured

A tree trunk is sliced into thin layers called veneer
-These layers are then glued together with the grain lines going in an alternate directions

Process on how Mdf(Manufactured timbers) is made

Wood dust and fibers are mixed with a glue and pressed into flat sheets under extreme heat and pressure

Advantages of Plywood(Manufactured timbers)

-Flat and structurally strong
-surface looks like wood
-resistant to warping, cracking and twisting

Disadvantages of Plywood(Manufactured timbers)

-quite expensive
-susceptible to water damage
-edges seem rough

Common uses of Plywood(Manufactured board)

Building and furniture panels that need some strength

Advantages of Mdf

• Cheap

• smooth ungrained surface good for painting

• Easy to use with machinery

Disadvantages of MDF

-Does not look good, needs to be coated
-weak compared to real wood or plywood
-Causes tools to blunt quicker

Common uses of Mdf

-Cheap flat-pack furniture, wall panels, cabinets

Process on how chipboard is manufactured

Wood chips are mixed with glue and pressed into flat sheets

Advantages of Chipboard(Manufactured board)

Uses waste materials so is cheap to produce

Disadvantages of Chipboard(Manufactured board)

-Not much structural strength
-Surface is very rough, so usually plastic coated

Common uses of Chipboard

Desktops, kitchen worktops

How does temperature affect where wood is grown

Topical climates tend to posses tropical hardwoods such as mahagony and jelutong, whilst cold climates posses softwood such as pine,cedar and larch
whilst temperature climates have both

Advantages of Mahagony

• has a very attractive finish

• Quite easy to work with

Disadvantages of mahagony

Expensive
environmental problems from sourcing
oils in the wood can give people rashes

Common uses of Mahagony

High quality furniture and jewellery boxes, windorss

Define Grain

Fibres that run the length of the tree trunk

Define Knot

Appears where a branch grew out of the tree, the grain swirls around and the wood can be harder

Define elasticity

The ability of a material to return to its original shape when applied force is removed

Define tensile strength

The amount of force a material can withstand when being pulled. The tensile strength for wood is 4 times the compresive strength

Impact of Logging on communities

-Can force indigenous people who live around the area out of their homes
-offers jobs
-brings money to the area

Recycling and disposal of timber

Natural timber is biodegradable and will rot in time, however manufactured timber cannot so disposing is harder. Some timber can be reused by cutting and altering their shapes for other purposes

Define processing

When a tree is felled, it needs to be processed to make usable timber. Tree trunks will be sawn into planks and then dried called seasoning/

Pollution of timber

When a tree is cut down or burned

Form

The overall shape and structure looks of a product. Some products being purely functional, some products are designed to look good

Define seasoning

Reducing the water content of timber from 10

Define warping

Bending or twisting of timber that happens as it is drying out

Define the environmental factors

• Sustainability - is sustainable sources are used-less damage for environment

• Genetic engineering - We are unaware of the long term effects of genetic engineered plants in the environment

• Seasoning - the process of removing moisture from timber to prevent warping

• Upcycling - the continued use of timber instead of burning it

Define the Availability factors

• stock materials - materials are sold in standard sixes

• Use of specialist materials - some specialist timber used for specific purposes eg marine plywood for outdoor use

• Natural disasters and disease

Treatments for timber

Timber can rot and burn away quickly. It can be treated with chemicals to reduce this. Timber can be pressure treated with preservative making it resistant to rotting

Forces that can act on materials

Compression - a squashing force like standing on something
Tension - A pulling force - like tugging on the ends of a rope
shear - forces acting on opposite directions eg cutting action of scissors

Define Lamination

Bonding several thin layers together to make a thicker material

Ways to strengthen timber

-lamination - good for curves
-Brace and tie bars
-Embedding compositie materials to a timber

Stock forms/types

Regular sections

PAR (Planed all rounded)

All four surfaces have been planed, it will have slightly rounded edges to make handling easy and safe. Constructional timber(frames for interior walls) are usually PAR

PSE (Planed square edge)

All four surfcaes are planed, but the edges are left square. Joinery timber is usually left as pse

Processes to cut and shape materials

Routing: A router contains a rotating cutter. Can be used with lots of different shapped cutters

Sawing: Used to cut timber into different shapes and sizes

Use of a mortiser: Creates square holes in the timber typically for a mortis and tenon joint

Use of a bag press: A bag press is a bag that can be sealed and have air sucked out. Used for moulding laminates

Types of Production

-One off: one product made at a time
-Batch: Several copies of the same product are made at the same time
-Mass: Factory machinery set up to make lots of identical products

Advantages of One off production

-No set up cost
-Made with existing equipment
-product can be customized to the users needs

Negatives of One off production

-slow - expensive to make several

Advantages of Batch production

-Jigs, templates and moulds speed up the process and can be kept for future use

Disadvantages of Batch production

-Labour intensive, so it is quite expensive per product
-Making jigs can be time consuming

Advantages of mass production

Can make a product quickly and cheaply

Disadvantages of Mass production

Machinery is expensive to set up and calibrate for certain product only tasks, only worthwhile for making lots of products

Advantages of Continous production

-Makes the product quickly and cheaply
-products can be perfected over time with small changes

Disadvantages of Continous production

-Machinery is very expensive to set up - only worthwhile for making huge quantities of a product

Define Jig

A jig can be put over a peice of work and guide a drill or saw to cut in a required place. Enables accuracy

Define fixtures

A fixture holds the workpecie in place while it is being cut or reshaped.

Define template

A template is a cut out shape that you can trace around to mark a unique shape. It is useful in production because it enables workers to outline quickly and accurately

Define subassembly

Components that have been assembled and used as individual components in a larger product.

Define CAM(Computer aided Manufacturing)

CAM uses a computer to control machines and equipment during manufacturing

Techniques for Quantity production

-Fixtures
-Jigs
-Templates
-Sub assembly
-Cam
-Quality control
-Working within tolerance
-Efficient cutting

Working within tolerance (Quantity manufacting)

Manufactured parts will always have a tolerance. That is the range of sizes within which the part is acceptable.
EG length of a Cut wooden plank is +

Efficient cutting to minimize waste

Wasting as little material as possible when making products

Wooden Butt Joint

Strengths: Easy to make, 2 square ends glued together
Weaknesses: No mechanical strength, 100% reliant on glue

Wooden Dowel Joint

Advantages: Automated machines can drill the dowel holes quickly and accurately
Weaknesses: Hard to align dowels by hand

Wooden Lap joint

Strengths: Easy to cut
Weaknesses: Not very strong

Housing joint

Strength: Pairs well with corner lap joints
weaknesses: Can be tricky to cut neatly on wide boards

Wooden mitre joint

Advantages: Looks good as no end grain shows
Weaknesses: Weak as its only a butt joint at 45 degrees

Wooden Mortise and tenon Joint

Advantages: A strong joint
Weaknesses: Time consuming to cut by hand however there are mortising machiens

Dovetail Joint

Advantages: Very strong joint, lots of surface area
Weaknesses: Difficult to cut by hand

Butt Hinge

Use: Doors
Stregths: Hidden from sight when door is closed
weaknesses: Hard to fit as an accurate slot needs to be cut both sides

Flush hinge

Use: Small cupboard doors
Advantages: Easy to fit as no slots to cut
Weakness: Leaves a gap between the door and frame

Butterfly hinge

Use: Screws onto the surface

T hinge

Use: Used for gates and shed doors
Advantages: Long bar good for supporting weight
Weakness: Sits on the front of door

Types of surface treatments and finishes for functional and aesthetic purposes

-Painting
-Staining :Coloured liquid that soaks on the wood surface
-Varnishing: A clear coat that dries to shine
-Wax: A soft solid rubbed onto surface with cloth
-Oil: Rubbed onto the surface and soaks in
-Shellac: A cloudy liquid made from resin, many layers rubbed on and polished
-Veneering: A thin layer of wood glue onto the surface

Advantages of Painting as surface treatment

-Available in many colours

Disadvantages of Painting as a surface treatment

covers up natural wood grain

Advantages of staining as a surface treatment

-Makes a pale coloured wood like pine darker to make it look like a more expensive wood

Disadvantages of staining as a surface treatment

Does not mimic/re[plicate high end wood color and texture as the grain still shows

Strengths of varnishing as a surface treatment

-Gives a hardwearing finish that shows the grain on the wood
-Can be high gloss or matte finish

Weaknesses of varnishing as a surface treament

Can scratch or chip and expose the wood

Advantages of wax as a surface treatment

-Easy to apply
-Gives a plain natural look

Disadvantages of wax as a surface treatment

-Rubs away and needs reapplying
-Not a glossy finish

Advantages of Oil as a surface treatment

-Good for waterproofing the timber
-Can potentially reduce fungal growth

Disadvantages to oil as a surface treatment

oily surface

Advantage of shellac as a surface treatment

-Traditionally used on expensive furniture for its glossy lustre