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Electronics

Potential Difference

Many Circuits use a change in the potential difference to operate certain chips and functions. Potential difference is achieved by connecting two resistors in series. The difference is then worked out by the formula (R2/(R1+R2))*V with R1 being the top resistor and R2 the bottom one. ==Food Technology == File:Headline textItalic text


--Spicey94 10:03, 21 April 2009 (BST)[[Image:Media:Example.jpg]] == ==

Product Design

Resistant Materials

Resistant Materials involves working with woods, metals and plastics. In GCSE Resistant Materials CAD and CAM is used. Useful revision website: http://www.technologystudent.com/

Materials

-Woods

-Metals

-Plastics

Woods

Woods can be classified into two types- softwoods and hardwoods. The use of the words 'soft' and 'hard' are not necessarily an accurate description of the wood's hardness- balsa is a prime example; it is a hardwood and yet lighter in weight than many softwoods.

Hardwoods come from deciduous trees, and tend to take around 100 years to grow. On the other hand, softwoods, which come from coniferous trees, only take around 30 years to grow. This makes softwoods cheaper and more commercially available than hardwoods.

Knowledge of some of the properties of certain softwoods and hardwoods is essential for the exam.

Beech: Hardwood, hard, tough, prone to warping

Oak: Hardwood, hard, tough, durable, heavy and contains an acid which can cause steel to corrode

Ash: Hardwood, tough, flexible

Pine: Softwood, knotty, prone to warping

Generally, softwoods are less dense than hardwoods. Hardwoods contain more fibrous material than softwoods.

Metals

Metals can be classified into 3 areas: ferrous, non-ferrous and alloys. Ferrous means the metal consists of mainly ferrite or iron. Ferrous metals are magnetic. Non-ferrous metals are not magnetic.

Popular metals include iron, mild steel, stainless steel, aluminium, copper, lead and tin.

Plastics

Plastics are split into 2 types: thermoset and thermoplastics. Thermoplastics can be re-moulded over and over again because they have very few cross links. Thermoset plastics, on the other hand, have molecules lined up and connected by cross links. This means they can be shaped for the 1st time, but after that, they form a rigid and permanent shape.

Thermoplastics: Acrylic, ABS and polyester

Thermoset Plastics: Epoxy Resin and Urea Formaldehye

Adhesives

Adhesives are used for the process of fabrication-joining one material to another. Joints which are made using adhesives are permanent. The most common school workshop adhesives are:

Polyvinyl Acetate: PVA, joining wood to wood, most types not waterproof

Contact Adhesive: Gluing large sheet materials together, takes 15-20 mins to dry, used for dissimilar materials

Epoxy Resin: Expensive, joining any materials, full strength 2-3 days after application Example: Araldite

Tensol: Gluing acrylic to acrylic, clear liquid

Safety when using adhesives: Harmful fumes may be given off, so application of adhesives should only take place in well-ventilated areas. Contact with skin should be avoided and an apron should be worn.

Fabricating: Joints

There are many types of wood joints used in manufacturing, from very simple ones to very complex ones. Here are the ones which are required for the exam;

Butt Joint: The simplest and weakest joint.

Lap Joint: Also known as a 'rebate' joint.

Mitre Joint: 2 pieces of wood at a right angle, cut at 45 degrees. Often used in picture frames and skirting boards.

Dowel Joints: A butt joint with dowels- acting as reinforcement.

Mortice & Tenon Joint: Very strong joint.

Other joining methods: Threading, rivets, brazing, soldering and welding/

Textiles

Useful Textiles revision website http://textiles4u.wikispaces.com/

Graphics

Pencils

The Lead on Pencils are actually GRAPHITE composites, a mix of clay and graphite. Pencils are graded with (H) or (B) according to the hardness and blackness of this composite.

Soft Pencils are ones with less clay but more graphite, meaning that the composite is darker and richer, but will wear down easily. They are graded form 9B to HB. These are commonly used for sketching.

Hard Pencils are ones with more clay but less graphite. The point of the pencil won't wear down easily. They are graded from H to 9H.

Materials and Components

Paper sizes are measured from A0 to A6, and the next number up is half the size of the previous one Paper is sold by weight in gsm (grams per square metre) up to 220gsm, at which point it is called board. Board is sold in microns (μm). There are 1000μm in 1mm.

Three main ways of achieving different properties of paper / card, the first two of which directly affect the brightness (whiteness) of the surface: Coating (eg china clay / chalk) sprayed on for a smoother finish

Sizing to improve the paper / card’s absorbency

Laminating layers of thinner card to achieve a board

Virgin paper or board makes up 90% of all paper - it is stronger and whiter, and usually is used for food because it reduces risk of contamination.

Recycled paper saves energy as less raw material is processed, and is good for the environment; however harmful chemicals such as bleach may be used to make the paper white, and recycled paper isn’t as strong.

Types of paper and board:

-cartridge paper

-layout paper

-bleed proof paper

-tracing paper

-card

-corrugated board

-mount board

-duplex

-solid white board

-grey board

Many paper based boards are laminated to other materials for specific purposes, (eg plastic coating for waterproofing)

aluminium foil coating for insulation or as a bacterial barrier

greaseproof paper for baking cups

wax coating for waterproofing (takeaway coffee cups)

Thermoplastics

-HIPS - high impact polystyrene is used in toys, jewel CD cases, yogurt pots, as it can be vacuum formed

-PP - polypropylene is flexible, used for crisp packets, resistance to work fatigue, hygenic

-PET - polyethylene terephtalate is tough, and used for fizzy drinks bottles

-PVC - polyvinyl chloride is tough and resists scratches, used for blister packs

-Expanded polystyrene (Styrofoam) - used for protective packaging, block modelling

-Acetate - clear but not tough, eg film for cameras

-Acrylic - stiff and brittle, high gloss and wide colour range, POS stands

-Bioplastic - biodegradable, used for food packaging

Shaping and Forming Plastics

-Vacuum forming is a process in which simple hollow shapes are created by sucking air from underneath a heated thermoplastic sheet (HIPS) draped over a mould (remember draft angles and rounded edges for the mould!)

-Injection moulding is a process in which hot liquid plastic is injected by force into a mould

-Blow moulding is a process for making hollow plastic forms by blowing compressed air into a heated thermoplastic

-Line bending is a process used to bend straight lines in a heated thermoplastic

-Jigs and formers are used to accurately locate, bend, or aid in the construction of a product, saving time by making it possible to create identical items

Block modelling materials

Expanded polystyrene (Styrofoam) is good for making 3D models but a high quality finish is hard to achieve (use a file or abrasive paper)

Balsa wood takes longer to shape compared to Styrofoam, but is stronger and can be used as a mould for vacuum forming (use a file or abrasive paper)

Plasticine or clay is easy to make 3D models and can easily be reused but does not have a good finish

Foam board can be laser cut is good for drawing onto or adding a printed image, but is not recyclable Spiral wound tubes are used in 3D printing

Smart materials - special materials which are affected by a change in their environment and respond to stimuli (eg temperature, light, pH)

Modern materials - new materials invented in the last 50 years

Polymorph is a special type of plastic which is hard at room temperature but softens at 60 degrees Celsius. Corn starch polymers are biodegradable and made from crops such as potatoes, corn and maize, and can replace oil based thermoplastics

Paperfoam is made from a combination of starch based polymers and paper fibres, and is scratch-resistant and fully biodegradable - used for packaging

PMC - precious metal clays - 99.9% metal, 0.1% clay, can be shaped at room temperature

Lyocell - biodegradable material made from wood pulp, used for tea bags

Thermochromic materials change colour depending on their temperature, and are used for thermometers - specific colours indicate different temperatures, so it is easy and safe to use

Photochromic / Electrochromic / Hydrochromic materials change colour depending on light / electricity / water present. (Uses: sunglasses / LCD displays / moisture testing for plant pots)

Phosphorescent materials absorb light during the day and give it off at when it’s dark (eg: watches that glow in the dark)

Glues

Glue stick - cheap, easy, safe

Polyvinyl acetate (PVA) - strong, safe, colourless when dry, but may ripple thin card if too much is applied

Spray adhesive - quick, clear spray, but needs to be done with a mask in a spray booth with extractor, and isn’t strong and is quite expensive

Balsa cement - quick-setting, clear smelly glue

Acrylic cement (‘Tensol’) - quick to apply and watery, but may leave marks is applied in excess

Epoxy reson - very strong and gloopy, light brown, sticks anything together but takes two hours to set, is difficult to apply and will stain paper or card

Hot glue gun - thick clear and stringy, sets quickly, and will join different materials together, but cannot be used on fine model work as it sets quickly

Double-sided tape - clear and white, immediate strong join, but cannot be repositioned

Tools!

Scalpels and craft knives

Scissors

Rotary cutters

Compass cutters (cuts circles in paper)

Fret / reciprocating saw (cuts plastic sheets or thick board and wood, can cut intricate shapes)

Die cutter

Hot wire cutter

Laser cutter

Bought-in components are individual pieces of a product that are connected to other pieces, which have not been made but have been bought in - eg:

LEDs

Fastenings (brass paper fasteners)

HDPE (high density polyethylene - thermoplastic used for strong containers / garden furniture)

Design and Market Influences

Designers

Designers influence new products

Harry Beck - non-geographical, topographical Tube Map (1933)

Alberto Alessi - stylish and creative product design

Jock Kinnear and Margaret Calvert - created road signs using different colours and shapes, and 2D block-coloured pictograms to convey meanings, as well as designing an easy-to-read typeface

Wally Olins - creates brands to help promote a company’s corporate identity

Robert Sabuda - creates pop-up books that use clever paper engineering for children and adults

Techniques and Processes

A model is a graphic representation of the item being designed, and is often a scaled-down version

A prototype is a life-size working model of a design, used for testing, development and evaluation

A mock-up is a working model (often full-size) of a design that can be evaluated and tested

Scale

2:1 - twice full size, used for small objects, eg earrings

1:1 - actual size, used for handheld objects, eg phones

1:2 - half size, eg laptops

1:10 - eg used for furniture

1:100 - eg used for a house

1:500 - eg used for a sports stadium

Target marketing is aiming a product to be sold at a specific group of people (eg laptops sold for students who need a portable ICT solution)

Gap in the market identification is used to promote a product that does something which isn’t already being done (eg the iPod) Sketching

[Be able to draw 2D / 3D freehand drawings using crating techniques / grids and underlays] Enhancement

[Be able to colour in to add visual impact] [Be able to texturally represent different materials and surfaces] [Understand contrasting, complementary, harmonising and monochromatic colour in terms of the colour wheel] Colour separation in commercial application is the process where the original image is separated into the four process colours (CMYK) by a computer program

Presentation

CAD - used for developing ideas using computers (eg ProDesktop and 2D Design) to save time and money, and to give an impression of what the product will be like in 360 degrees

Typography - font is a specific letter type (Times New Roman 12pt Bold, typeface is a style of text (Trebuchet MS) Serif / sans serif, kerning (letter spacing)

Never use Comic Sans!

Encapsulation protects a printed product by encasing it by a thin layer of plastic on both sides by using heat, providing a high gloss finish and a wipe-off surface

Pictorial Drawings

[Be able to one-point and two-point perspective and isometric sketches] Working Drawings

[Be able to understand third AOP drawings, exploded / sectional drawings / site plans and maps]

Surface Developments (Nets)

[Understand how 3D containers are manufactured from nets, often with CAD/CAM]

Information Drawings

Data can be represented graphically in 2D or 3D bar and pie charts, line graphs, and pictographs Signs give instructions or warnings (eg road signs) and may include a symbol to help communicate information - they should be eye-catching and easy to understand, such as pictograms

Labels are attached to products and convey information (eg it is a legal requirement to include ingredients, weight, and allergy advice on food packaging)

Symbols are visual devices used to communicate

Ideograms are pictorial symbols used to convey a message

Pictograms are simple ideograms without language that are used in public places

Flowchart symbols

Terminal = rounded rectangle

Process = sharp rectangle

Decision = diamond

Input/Output = parallelogram

Feedback loops show where to go back to if necessary

A sequential illustration is a series of drawings that show the steops in the process of making something (eg LEGO building instructions, Ikea furnitre)

Schematic maps show the connection between places but not the distances or geographical locations (eg London Tube Map)

Paper and Card Engineering

Products and Applications

A product lifecycle is the stages that a product goes through when it goes on sale

Introduction - usually slow sales at launch, and high costs from developing and advertising the new product, hence profits are low

Growth - the product’s popularity increases, so profit is boosted

Maturity - demand hits a peak because most who will buy the product have done so, (so profit peaks) and competitors launch their products

Decline - sales slow down and profits reduce

Products can be rebranded and targeted at totally different target markets once it hits it’s decline (eg Lucozade was targeted as people recovering from illnesses, now is targeted at sports people)

The quality of a graphic product is judged by whether it meets a need, the fitness of purpose, the appropriate use of materials and time taken to develop it

Evaluation Technique

Evaluation is the process of enquiring how well the product meets the specification

Testing is the process of checking that occurs at regular stages throughout the design process

Evaluation of a product is important because it contributes to designing on-going improvements for that product

End-users’ opinions are hugely important because they will end up using the product

Formative evaluation is ongoing evaluation such as testing materials, construction, components, safety, colour schemes, imagery, etc

Summative evaluation is the testing that occurs at the end of a the design process, when the final product is tested against the specification - it ensures that the product suits the purpose it was made for / illustrates possible improvements Social / Cultural / Moral / Environmental / Economic / Sustainability Issues

A moral issue is when a designer considers whether something is dangerous or controversial, and is usually related to a specific target market (eg size of jigsaw puzzle pieces - can children choke on them? Are they large enough to hold?) A social issue is when a designer considers the interest of the consumers, and usually relate to the wider public in general (eg fast-food advertising for children)

Cultural issues are dependant on the target market, (eg large green ‘Vs’ to show a product is suitable for vegetarians, certain colours / numbers in countries)

Ergonomics is the study of how products can be shaped and sized to fit with the human body

Anthropometric data should be used when designing products

Certain environmental logos are found on products and packaging:

d2w = a biodegradable plastic, and the symbol is found on products

FSC = the Forest Stewardship Council which manages the replanting of forests

The Green Dot shows that the manufacturer has contributed to the collection and recycling of the product Economic

A product is ‘designed to fail’ if the designers and manufacturers have plan the ‘built-in obsolescence’ in order to generate future sales Built-in obsolescence is when a product is made with one or more components that are known to fail after a specific period Sustainability

The 6Rs: Repair / Reduce / Re-use / Re-think / Refuse

Primary packaging protects the product and gives key information about storage and contents (eg cereal box); secondary packaging contains the actual product (eg the bag inside a ceral box)

Eco-friendly packaging solutions are being developed, eg, PaperFoam which is recyclable and biodegradable

The waste hierarchy pyramid:

Prevention (eg apples!)

Minimisation (eg Easter eggs)

Reuse (eg food containers)

Recycling

Energy recovery

Disposal

Information and Communication Technology

CAD = Computer Aided Design (producing design using a computer)

CAM = Computer Aided Manufacture (producing products using a computer)

CNC = Computer Numerical Controlled (machines controlled by a number system)

Electronic transfer of data permits designing and manufacturing activities to take place in different geographical locations Health and Safety Issues

Safety advice when using adhesives and solvents:

Always use in a well-ventilated area

Read instructions

Safety advice when cutting with a sharp object:

Keep fingers away from the sharp edges

Use a safety rule with a raised edge

Cut away from yourself

Use a cutting mat on a flat surface

When using a fretsaw ensure that you wear eye protection, and that the machine guard is positioned correctly

Risk assessment is working out what the hazards are in a particular situation and deciding what you are going to do about them

The Health and Safety Executive (HSE) is a government body responsible for ensuring workplaces comply with health and safety at work laws

The British Standards Institute is a body that is responsible for:

Warning signs - eg danger of death signs (triangular, yellow and black)

‘Do Not’ signs - eg No Smoking (red circles with diagonal lines to cross out a pictogram of lit cigarette)

Must Do signs - eg switch off all mobile phones (blue circle or rectangle

Safety signs - eg First Aid Kits (white cross on green background)

Processes and Manufacture

Systems and Control Procedures

Quality assurance is the process through which the designer actually states what qualities he or she wants the product to have - to make sure it is fit for purpose

Fit for purpose means a product performs its designated function properly (eg a smoke alarm should sound if it detects smoke, a pencil sharpener sharpens pencils), and how ergonomic the design is for the cost - confirmed by testing against target market and original designer specification and collecting feedback (ACCESSFMM)

If packaging is fit for purpose then it performs these functions - stacking and storage (eg effective use of space), information (tells consumer necessary safety hazards and instructions about product), protection (for mass transportation eg nets), preservation, promotion (colour and aesthetics) ('SIPPP')

Quality Control is the measures that are put into place to ensure that the quality standards are met at critical points of the production process (eg before mass printing/production)

Tolerance is the acceptable range of accuracy

Methods of quality control

Registration marks are used to make sure the printing plates line up, otherwise the printed image can appear fuzzy or out of focus (around 10mm)

Colour bars (CMYK) and tone bars are printed to make sure the right colours are printed - these can be checked with a densitometer but are usually visually checked

Sampling is carried out to check for accuracy, to compensate for tooling wear of colour alignment failures (usually 1 in 50 or 1 in 100)

Crop marks are located at the four corners of the printed sheet showing where the image should be cut

Bleed areas are the 3mm extra area at the edge of a printed image, that allows for slight misalignment when cropping the image

Pop-up cards are designed to create interest by the use of mechanical action, and card mechanisms can create a variety of movements, including rotary, linear, reciprocating and oscillating

The main elements of a card mechanism are fixed and floating pivots, and levers are joined together to create the motion

Industrial Practices

Scale models and prototypes are important in product development as they are used for testing and feedback The four production processes:

One-off (1) - easy to set up and change, very high individual cost (eg paintings, sculptures which are made by an individual or group especially)

Batch (2-10,000) - adaptable process of making, quite easy to change, machines are expensive to buy and set up (eg books, perfume bottles, POS displays)

Mass (10,000+) - low individual cost of item, but more expensive than batch to set up (eg cars)

Continuous (millions, 24/7!) - easy to make the same item cheaply to a high standard, but cannot change if demand falls (eg making glass, paper, blank products such as cans, etc)

JIT - Just-in-time is a specific method of controlling stock in which a company only buys in enough materials to cover its immediate needs

Reduced storage costs

Production run can be more easily changed

Reduced over-stocking of product

Printing process:

Pre-press (artwork, colour separation, QC checks, plate alignment)

Print (regular QC checks on plate alignment and colour density)

Finishing (special effects such as foil blocking, laminating, varnishing, print is guillotined to size, print is packed and distributed)

Commercial printing methods:

Offset lithography

The aluminium (or card for short print runs [~5000!]) printing plates never touches the paper, because the image is transferred ('offset') onto another cylinder

PMT (photomechanical transfer) is the process that transfers the image onto the printing plate using UV light

Sheet fed is individual pre-cut pieces of paper being fed into the printer

Web fed is when paper is fed into the printer on huge rolls, which are cut after printing

Inks are either oil-based of water-based

Flexography is a high speed, high volume print process that can print onto nearly all surfaces

Gravure is the highest quality and most expensive print process used for detailed images (eg stamps)

Screen printing is a low quality cheap print process that can print onto fabrics (eg t-shirts)

Digital printing divides the print into CMYK but does not need printing plates to achieve a high quality print, however price-per-unit is relatively high compared to other methods - thus it is used for 1000-3000 copies, where setting up offset lithography would be more expensive

Types of print finishes:

Varnishing / spot varnishing - can be matt / satin / gloss

Foil blocking - adds quality, looks expensive, uses heat and pressure

Laminating (one side is plastic) - improves strength, adds wipe-off surface

Embossing - raises surface of material using a press, massively expensive

Die-cutting - cuts, scores, or creases shapes in card using a press forme

The four process colours are cyan, magenta, yellow, and the key, black (CMYK)

Special colours are pre-mixed specific colours that can be used instead of the CMYK system (eg fluorescent or metallic colours)

Uses of packaging: stacking and storage, information, protection, preservation, promotion ('SIPPP')

Barcodes are scanned by computers, and generally contain information about the product's country of origin, the manufacturer's reference number, and the specific product number.

An RFID tag is a microchip (size of a grain of rice to size of a small paperback book) combined with an antenna in a compact package, and can be read from over 100 feet away as well as being able to contain far more information than a barcode A patent is a legal protection that the designer has for their design to prevent it from being copied for up to 20 years

Copyright is used to protect text, music, films, drawings, etc from being copied for the lifetime of the creator plus 70 years (shown by a © sign)

Trademarks are distinctive symbols or logos that contain the company name or slogan and cannot be copied which usually cost £200 to be registered, and are shown by a TM mark (eg Apple, HMV, Sony)

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