Design and TechnologyDesign and TechnologyResistant Materials GCSE

Mr Rayworth

WoodWood

Hardwood Softwood Manufactured Boards

How is it Made?

Grown in the UKBroad leaf Deciduous trees (lose leaves)Expensive

Imported to the UKNeedle Leaf Conifer Trees (Ever green)Average

Man Made

Cheap

Properties Tough DurableGrain

Light WeightWeaker (Contain Knots)

Solid/Stable MaterialLarge Boards/Variety of sizes

Uses FurnitureToys Tool Handles

Building ConstructionPaneling

FurnitureDraw Bases

Examples Beech (pink)Oak (light brown)Mahogany (reddish brown)

Pine (cream/pale brown)Cedar (dark/reddish brown)

Block boardPlywoodMDF (Medium Density Fibreboard)

Can you identify these?Can you identify these?

MetalsMetals

Ferrous Non-ferrous Alloys

Properties Contains iron and small amounts of other metals or elements.MagneticRust (Requires coating such as enamel, paint or galvanizing)Strong

Does not contain iron.No Rust (many don’t require coating.)Good for use with water.More expensive

Mixture of 2 metals to produce a new metal material.Heavy, and stronger (harder)

Uses Garden toolsWorkshop toolsNails/ScrewsCar brake discs

PansWindow framesJewelryPlumbing fittings

Taps/valvesSculptures/statuesCasting

Examples Cast-ironMild steelStainless steel

CopperAluminumZincGold

Brass Bronze

Plastics

Thermoplastics Thermosetting plasticsProperties Can be reshaped when reheated.

Good electrical/thermal insulatorsCant be reshaped when heated, once formed retains its shape.Harder materialMore expensive

Uses Drinks bottlesBuckets/pipesCable insulationCosmetic bottles/food containersSupermarket bags

Saucepan handlesLight switches/plugsBoat hulls

Examples PET (Polyethylene terephthalate)HDPE (high density poly ethylene)PP (Poly propylene) PMMA (Polymethyl-Methacrylate) – Acrylic)

Epoxy resins (adhesive)Melamine formaldehydePolyester resins

Composite Materials

Composite materials:GRP – Glass reinforced plastic, strands of glass fibres that have been coated in polyester resin. Can be moulded into shape, improves strength and toughness of the material.

Carbon fibre reinforced plastic, similar to GRP, carbon strands that have been coated in polyester resin. Stronger, tougher and lighter than GRP.

Kevlar, strong plastic materials woven to form a mat. Used in body armour, bullet proof vests for the army and police. Lighter and stronger than carbon reinforced plastic.

Smart Materials

Smart MaterialsPolymorph – plastic granules. When heated can change from a solid to a mouldable state. Shape can be changed when reheated. Good for ergonomic handles.

Thermo chromic – has the ability to change colour as the material changes temperature. Used in everyday technology such as Russell Hobbs kettles.

Shape Memory Alloys – Can change shape when heated. Nitinol is used for teeth bracing, when heated the length shortens, pulling teeth back into shape. Memoflex spectacles can be bent and twisted and will regain its original shape.

Sustainability of Materials

A sustainable material is a material that can be replaced continuously, or reused and recycled indefinitely.

MotionsMotions

Motion types:

Linear

Reciprocating

Oscillating

Rotary

Mechanisms – Gears (Rotary)Mechanisms – Gears (Rotary)

Mechanisms change input motions into output motions.

A mechanism is used to make a task easier to complete.

Gears – toothed wheels that interlock.

Driver – turned by hand or motor.Driven – turned by driver gear.

Turn in different directions – Driver clockwise = Driven anticlockwise

Mechanisms – Chain and SprocketMechanisms – Chain and Sprocket

Good example of a chain and sprocket mechanism is a bike chain. Two sprocket wheels (toothed wheels) are linked with a chain (multiple links)

Advantages of this mechanism – it cant slip like a belt drive could.

Disadvantage of this mechanism – needs maintenance (cleaning and oil lubrication)

Mechanisms – Belt DriveMechanisms – Belt Drive

A belt drive transfers movement from one rotating shaft to the other.

Belt drives are used often in pillar drills.

The flexible belt links the motor to the drill shaft, and can be placed in different positions to make the drill turn faster/slower.

Disadvantage – the belt can slip

Mechanisms – PulleysMechanisms – Pulleys

Pulleys make lifting a load easier.

A single pulley changes the direction of a force required, for example in order to lift an object a crane has to pull down.

Mechanisms – CamsMechanisms – Cams

A cam mechanism has two main parts – the cam and the follower.Cams come in a number of shapes and sizes but the will always rotate (rotary motions)

The follower will rest on the cam and ‘follow’ its shape (sometimes the follower may have a small wheel to reduce friction)

The follower moves up and down as the cam turns.

Mechanisms – Mechanisms – Cranks and LeversCranks and Levers

A crank can be a simple arm on a shaft with a handle, or a pedal on a bike/go kart.

The longer the arm of the mechanism is the easier it is to turn the handle. (Allen Keys)

When a crank or several cranks are directly on a shaft it is known as a crank shaft.

Levers are used to give a mechanical advantage, to make it easier to move or lift an object.A pivot/fulcrum is used to reduce the effort, the closer the pivot is to the load the easier an object becomes to lift.Scissors are an example of two levers working together with 1 pivot point.

Wood JointsWood Joints

Wood can be joined together in several ways.There are a number of different joints that can be used for a number of different purposes.Wood joints are often glued also to make them stronger and more secure.

Butt joint – weaker joint, but quick and simple to produce. Used to produce cheap furniture.

Mitred joint – similar to a butt joint but more aesthetic. They are more difficult to cut because of the angle and will have a larger gluing area. Used to produce picture frames, door frames etc.

Lap joints have a larger surface area for gluing than a butt joint which makes them stronger. Used to create drawers and boxes.

Wood JointsWood Joints

Dowel joints use a wooden or plastic peg called a dowel, which fits into aligned holes to reinforce the joint. They are often used in factory produced furniture.

Mortise and Tenon joints are really strong and are often used to produce tables and chairs.

Halving joints are fairly strong and have a large surface area for gluing. This type of joint is used to create frames, and frame construction.

Housing joint – this type of joint it used in shelving units, they have a good surface area for gluing, and provides support along the length of the joint.

Dovetail/finger (comb) joints are attractive and strong joints, used often in drawers and furniture, but are harder to create.

Components and AdhesivesComponents and Adhesives

Hinges are available in a number of materials (steel, brass, nylon) and can be coated to match a piece of furniture. The part of a hinge that moves is known as the knuckle.

There are 4 different types of hinges;

Tee hinge – often used for sheds and garden gates. (outside) the longer ‘strap’ allows the hinge to support a greater weight.Butt hinge – most common hinge used for doors. One part of the hinge is set into the door and the other into the door frame.Pivot hinge – this type of hinge allows you to life a door from its frame, again one part is screwed to the door and the other into the frame.Flush hinge – this hinge is screwed directly to the surface and are much easier to fit than a butt hinge. They are often used to lightweight jobs.

Components and AdhesivesComponents and Adhesives

Knock down fittings (KD)These are non permanent joints, usually locks and brackets (plastic/metal) which allows something like furniture to be assembled and taken apart again easily.They are used instead of traditional wood joints, they are fast to use but not as strong as a glued wood joint.Knock down fittings are assembles using screwdrivers and Allen keys.

Catches are used to hold doors closed without locking them.They can come in a variety of types including, magnetic, spring catch and ball catch.

Components and AdhesivesComponents and Adhesives

Screws and bolts are used with wood, metals and plastics, and there are different types available to use with each of these materials. Wood screws often require a pilot hole to be drilled before the screw is inserted. As the screw is turned by the screwdriver, the thread pulls it into the wood. The screws have a different type of head for the jobs for example round, countersunk, slotted and cross heads. Self tapping screws have hardened threads and are designed to cut there own threaded holes in hard materials such as metals and hard plastics.Machine screws have a straight shank and are used with washers and nuts, the head types vary and can be tightened with a screwdriver or Allen key.Screws and bolts are usually made from steel, brass or stainless steel.

Components and AdhesivesComponents and Adhesives

Adhesives are used for jointing materials together. You should use different adhesives for different types materials. PVA – Polyvinyl Acetate is used for wood.There are two types of PVA, one can be used for interior work, and one for exterior use. This means that one is waterproof and the other is not. PVA for use outside is more expensive but can withstand damp.Contact adhesives are very strong, it is usually rubber based and is used for household items like floor tiles. It is applied to both surfaces and left to go tacky until it is applied. Contact adhesives can give off harmful fumes so need to be applied in well ventilated areas. Epoxy resins (Araldite) is two substances that are mixed in equal parts, both a thick liquid (one is clear and the other yellow)Once the two substances are mixed they will stick almost anything, ceramic to ceramics, metals to woods, woods to plastics etc. Epoxy resins will need about 15 minutes to harden and can be more expensive.

Components and AdhesivesComponents and Adhesives

Superglue also sticks most things. Superglue is however more expensive than an epoxy resin. It will stick to skin so care is required.Superglue is a clear thin liquid, after application the glue will require some small pressure to create a strong bond.

Acrylic cement is used commonly for plastics. Tensol is a good example. Tensol is used in orthopaedic surgery to attach artificial joints to bones. It is a watery, clear liquid and requires a tight clamp to press the two materials together for a period of 24 hours. Tensol generates very strong and harmful fumes, so a well ventilated space is required.

Tools and Equipment – Hand toolsTools and Equipment – Hand tools

Coping Saw – for cutting curves into wood or plastic.

Hacksaw – used to cut metals and plastics.

Tenon Saw – used to cut wood.

Panel Saw – straight cuts into larger pieces of wood.

Junior hack saw – cuts smaller and more delicate metals and plastics

Tools and EquipmentTools and Equipment

Bench hook

Hand Drill

Marking Gauge

Plane

G-Cramp

Tri-Square

Mallet

Pliers

Vice

Chisel

File

Tools and EquipmentTools and Equipment