DT GCSE AQA

3 Main elements of a system

Input, process, output

What are systems used for?

To add additional functionality to designs

What is an input

component which either adds energy or information to a system

example of an input

switch

sensor

what are programmable microcontrollers

computer chips that can be programmed to perform specific tasks

what do programmable microcontrollers do

provide functionality and intelligence to products and systems

what can programmable microcontrollers do

Counting

Timing

Decision making

Advantages of programmable microcontrollers

Reduces size of circuit - programming replaces physical components

They can be reprogrammed many times - so changes can be made without replacing actual components

They have pins for connecting several input and output devices - adding to flexibility

What is an output

components which provide information to the outside world

Examples of output components

lamp or buzzer

components that emit light and sound

What products use output components

speaker

What products use input components

keyboard

webcam

microphone

what is a design brief

A design brief is the statement a client gives the designer outlining what they want their product to be like

What is a design specification

List of criteria a product needs to address.

functionality

application of use, ease of working

aesthetics

surface finish, texture, colour

environmental factors

could materials be renewable

could they be upcycled

which material would have the least environmental impact

FSC - forest stewardship council

Availability

ease of sourcing and purchase

Social factors

social responsibility

cultural factors

sensitive to cultural influences

What is collaboration

Working with others on proposals and solve problems as well as gathering data.

advantages of collaboration

improve range and quality of items

designers can feed off the ideas of others

disadvantages of collaboration

issues with communication

different time zones

different access

different units of measurement

what is User Centered designed

product is designed to fulfill the wants and needs of the consumers

advantages of user centered design

helps companies understand any potential issues and how the product can be modified even after the launch

disadvantages of user centered design

extra time

not targeted towards overall market

cost

what is systems approach

Plans the layout for the correct inputs, processes and outputs things that need logical and ordered methods

advantages of systems approach

easy to understand

disadvantages of systems approach

might need to be edited a lot

may be issues with programming

what is iterative design

each iteration gets better as a result of the small refinements being made after each design

iterative design advantages

leads to desired quality and functionality

iterative design disadvantages

time consuming

uses lots of material

high cost

How to avoid design fixation

use of mood boards

different approaches to design generation

• modelling

• quick sketches

• CAD

  abstract drawings which can be interpreted

what are the different types of movement

linear

oscillation

reciprocation

rotary

First order lever

• pivot point in center

• load then pivot then effort

• e.g. seesaw

Second order lever

• pivot point at one end

• load in the center

• effort at opposite end to point

• e.g. wheelbarrow

third order lever

• pivot point at one end

• effort in middle

• load at opposite end to point

• e.g. tweezers

how to calculate mechanical advantage

load = mechanical advantage x effort

Bell crank

used to change the direction of movement through 90 degrees using 2 moving pivots and a fixed pivot point

push-pull

also called parallel motion linkages

input and out motion the same

they may be created for avoiding a fixed component or making 2 parts of an object move at the same time

CAMS and followers

used to convert rotary movement to reciprocating movement

Circular cam

• off center pivot - follower moves um and down

• e.g. pistons or steam engines

Pear cam

• stationary for half a turn then rises and falls gently

• e.g. carousel horses

Snail or drop cam

• remains stationary for half a turn then rises and falls quickly

• only rotate in one direction

• drops at regular intervals

• e.g. production lines - make regular cuts

heart-shaped or constant velocity cam

• follower rises and falls steadily with uniform velocity

• no stationary period

flat follower

• flat bottom that sits on the cam

• cope well under load

• aren’t accurate

• lots of friction

Point or knife follower

• very accurate

• quick to wear away at the pointed edge

roller follower

• accurate

• low on friction

• can withstand load

• more costly to produce

what are gear trains

series of cog wheels

drive gear is powered and other gears are driven by this wheel

what are pulleys and belts

create a mechanical advantage for moving objects

prototype

• a single sometimes highly specialised item is produced

• workers highly skilled

• unit cost higher

• prosthetics, machinery, wedding dresses

personalisation

• mass produced item adapted to an individual

• personalised coffee cup

Batch

• usually up to 1000 units

• works along various different production points where different processes are complete

• workers skilled in a few different processes

• used for seasonal products or if only a limited number of products are needed or the product is seasonal

mass

• large scale

• automation may be used in the factory where large amounts of CAD/CAM is used

• injection moulding or casting may be used

• high set up costs

why are product manufactured in various ways

Products are manufactured in various quantities, depending upon demand and the requirements for the product.

continuous

• mass production - products are made 24 hours a day 7 days a week

• low cost consumable items due to high demand and continuous nature

• e.g. toilet paper

what is a production aid

They are used to ensure the shape of your design is accurate and can be used repeatedly to ensure the same shape is produced each time.

what is a jig

holds a material in place and guides cutting told to ensure that a process can be repeated accurately and consistently.

what is a former

solid shape that is placed in a vacuum former to create a hollow mould

What is a template

tool used to mark out shapes repeatedly - ensuring information is being placed correctly

what is a mould

a cavity or matrix that shapes a plastic or fluid substance into a desired product - the substance is poured or forced into the mould then allowed to harden

what is a die

wooden block with mounted steel knives used to cut, crease and perforate card and paper - used to cut precise shapes from various materials.

Hardwood properties

• Sourced from Deciduous trees

• Slower growing

• More expensive than softwoods

• Worldwide

Types of Hardwood

• Beech

• Oak

• Mahogany

• Balsa

• Ash

Softwoods Properties

• Coniferous trees

• Faster Growing

• Cheaper than Hardwoods

• Used by inexpensive furniture brands

• Prone to having knots

• Knots can affect the structure of the woods and leave holes id the dop out when dried

Types of softwoods

• larch

• pine

• spruce

Manufactured Boards properties

• Manufactures from timbers combined with adhesives

• Can be made from waste material

• Available in large consistent thickness sheets without faults

• Suitable flat pack furniture

• Can have a veneer pf plastic or tin wood attached to disguise the board and make it more attractive of functional

• can be recycled

Types of Manufactured Boards

• Medium Density Fiberboard

• Plywood

• Chipboard

Stock Forms of Manufactured Boards

• Boards - varying thicknesses

• Mouldings - Dowels, crown, pediment, dado, reed

• Planks - varying thicknesses up to 3600mm lengths

Why standardized sizing

• consistency of manufacture

• availability of specific sizing

• availability of materials

• components can be efficiently arranged to reduce waste and costs

• quality materials are used in manufacture

Examples of Standard Components

• Butt hinges

• Piano Hinges

• Countersunk screws

• pan head screws

• slotted screw

• corner block fitting

• cam lock fitting

Absorbency

The ability of a material to take in moisture

Density

The mass of a material in a standard volume of space

Fusibility

The ease at which the material can be fused together or the temperature required to melt

Conductivity

• electrical - allows the flow of electricity to pass through it

• thermal - allows heat to transfer through it

• insulation - the ability of a material to prevent the transfer of heat or electricity

Strength

• Compressive - the ability to withstand being crushed or shortened by pushing forces

• Tensile - the ability to resist stretching or pulling forces

Hardness

The ability to resist abrasive wear and indentation through impact

Toughness

The ability of a material to withstand an impact

Malleability

The ability of a material to bend or be hammered into another shape without breaking

Ductility

The ability of a material to be drawn out into wires

Elasticity

The ability of a material to be stretched or deformed and then return to its original shape.

What contributes to choosing materials

• Cost

• Availability

• Working properties

Process of Timber production

• Trees are felled

• Branches removed

• Cut to a suitable length to transport

• Logs to timber mills

• Timber is debarked and converted into planks

• Planks are seasoned

• Moisture levels are reduced to 6-8% for internal use and 9-14% for external use

• Timber if checked for warping, cracks and damage

• Maybe PAR

Examples of Timber Conversion

• Through and through sawn

• Quarter sawn

Air seasoning

• A structure with a solid roof and open sides is used to ensure there is airflow around the timber

• Timber is stacked using spacing

• Dried naturally

• For 25mm woods 3-4 months for softwoods 6 months for hardwoods

Kiln seasoning

• Timber is stacks within the kiln and spacing planks are used

• water is heated to produce steam

• over time the humidity

• Timber remains in the kiln for 2-5 days

Warping shapes

• bow

• crook

• kink

• cup

• twist

how MDF is made

• trees are felled

• timber is debarked

• broken down into chips

• wood chips washed

• Further broken down into fibres

• wax and resin is mixed in

• pressed and heated to the desired thickness

• it is sanded

• cut to shape

manufacture of plywood

Gluing at least three layers of sheet timber together at right angles to each other - laminating

Examples of wastage processes

• cut

• saw

• drill

• chisel

• sand

• plane

Surface treatment step by step

• Timber is assembled

• filler is applied

• sanded low grit 40-80

• finer grit 120-180

• finer grit 220-240

• primer applied paint primer needed, stain/ varnish - no primer needed

• if primed the primer will be sanded with a fine grit 240 grit paper

• final finish

Wax

• applied with a cloth with a direction of the grain

• Multiple layers needed to be applied to achieve the required finish

• can be applied over paint

• does not yellow or crack over time

Varnish

• applied with a brush

• can be oil or water based

• provides a tough water resistant finish

• available in a variety of wood colours

• dries slowly, can be difficult to clean

• discolours over time

Oil

• rubbed into the grain with a cloth

• multiple layers required

• easier to apply than wax and more durable

• longer drying times

• easily repaired

Paint

• applied with a brush

• knots can produce stains if not sealed

• A primer or undercoat is needed to prepare

• wide variety of colours

• can crack and discolour over time

Spray Paint

• health and safety consideration needed for application

• well ventilated area and mask required to ensure it is not inhaled

• primer/ undercoat required

• wide variety of colours

Lamination

Process used to create curved shapes in Timber

• layers of thin timber is glued together and clamped

Living Hinge

Cuts which allow the timber to flex. They can then be laminated.

What are Alloys

Alloys are a mix of a minimum of 1 metal and other materials. Often to change their working properties.

Examples of Metal

• Brass - Copper and Zinc

• Stainless Steel - Iron, Chromium and Carbon

• High speed steel - Iron, Carbon, Chromium, Tungsten