DT WJEC Revision Notes

8/10/2019 DT WJEC Revision Notes

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DT: SECTION A

Product Specification and Analysis:

The probable specification for the product;

The aesthetic appeal of the product; The function and/or purpose of the product;

Quality issues relating to the product;

The size data of the product;

The safety considerations of the product with reference to the end user;

The materials used in the manufacture of the product;

The scale of manufacture used to make the product;

The commercial processes used to make and assemble the product;

Safety considerations for making the product;

Sustainability and environmental issues.

Scales of Production:

One-off: highly skilled workers needed, high cost to produce/ made to order, personalized,

broad work tasks/ unique product made one at a time/ wedding cakes, tailored suits.

Batch: more costly then mass/ less labour intensive, general machinery/ a small or large

quantity made in batches/ fresh food, seasonal products.

Mass: specialized tools, high capital costs/ narrow work tasks. Low product cost/ made

continuously to match demand/ pencils, cars, phones.

Sustainability:

Reduce-is it possible to reduce the amount of materials used? This will help to protect

valuable resources.

Rethink- is there a better way to solve this problem that is less damaging to the

environment?

Refuse- this means not accepting things that are not the best option for the

environment. For example, is the packaging really needed?

Recycle- could recycled materials be used, or is the product made from materials that

are easy to recycle?

Reuse- could the product have another use? Could its parts be used in other products?

Is this information clearly communicated on the product? This will extend its life.

Repair- is the product easy to repair? This will extend its life.


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The Design Process:

Identify a Need- identify a Need or Purpose in a given situation.

Design Brief- produce a short Design Brief.

Tasks Schedule- List all major areas of work and allocate times and deadlines.

Analysis of Brief- Look at the Brief and produce a list of research questions.

Research- Identify and collate information only relevant to the Analysis of Brief.

Specification- Produce a list of design requirements found from research relevant to

the Brief.

Generate Ideas- Generate a range of different possible solutions satisfying the

Specification.

Choose Solution- Produce a solution to the Brief using the Specification and your

Generated Ideas.

Develop Solution- Generate details necessary to make the solution.

Make Solution- Produce the solution.

Test Solution- Test your solution against the Brief and Specification.

Modify Solution- List modifications to improve the solution's effectiveness.

Evaluation- Evaluate the project against the Brief and Specification, giving

recommendations.

Computer-aided design:

When a circuit has been finalised, a printed circuit board is usually designed and manufactured.Specialist software can be used to plan where the tracks, pads, strain holes and mounting

holes will be on the PCB.

CAD software can also be used to design the structure or packaging of control systems.

Software can also be used for writing the program used in microcontrollers. It is written in

programme-editing software (Picaxe Programming Editor) before being downloaded onto the

chip.

Advantages and disadvantages of using CAD

Advantages

Can be more accurate than hand-drawn designs - it reduces human error.

You can save and edit ideas, which makes it easier and cheaper to modify your design as

you go along.

You can modify existing ideas, which saves time.

Disadvantages

The software itself can be expensive so initial costs are high. There are free software

packages though.


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Staff need to be trained how to use the software, which also adds to costs.

Requires a PC.

Computer-aided manufacture:

When a PCBlayout has been designed using CAD, the board can be produced or manufactured

using CAM.

Two examples of CAM are:-

1. A design machined by a computer numeric control (CNC) miller, which removes all the

unwanted copper from the board.

2. A design layout printed on to acetate and transferred to a copper-clad board using

the photo transfer method. The unwanted copper is removed using acid.

Advantages and disadvantages of using CAM

Advantages

In large-scale production, the results are consistent (always the same).

Enables very high accuracy levels in large-scale production.

Usually speeds up production of low-volume products.Disadvantages

The software itself is expensive so initial costs are high.

Can be slower than traditional methods for one-off or low-volume production.

Staff need to be trained how to use the software and machinery, which adds to costs.

Jonathan Ive

Principal designer iMac and iPod.

Modern day legend not known by the public.

Liked to use translucent colours.

USPinternal control system visible

Trend of using two or three main colours.

Minimalistic/ simplistic forms.

Tropical colours/names - locations

Metallic forms and shades/ chrome.

Elegant form, geometric shapes.

Slim line approach.

Many new products feature bright colours.

Many new products feature transparent cases.

Shigeru Miyamoto

Description of Work:

When the Nintendo Company began branching out, Miyamoto helped design the

companys first original coin-operated arcade game Sheriff.


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Was told to redesign unsold radar scope units into a new arcade game.

Came up with Donkey Kong.

Developed Mario and platform games.

Super Mario and Mario Bros.

Made games for the first Nintendo 64.

Mario series spin-offs like Mario Kart 64 and Mario Party.

Impact of Work:

Miyamoto is seen as the leader of the development of handheld gaming.

Pioneer of platform games systems.

Lifetime achievement award winner at Game Developer Choice Awards 2007

Voted Ultimate Development Hero.

Provoked competitors like Sony to follow his style.

DT: SECTION B

Scale:

One-off productionis when only one product is made at a time. Every product is

different so it is labour intensive. Products may be made by hand or a combination of

hand and machine methods.

Batch productionis when a small quantity of identical products are made. Batch

production may also be labour intensive, but jigs and templates are used to aid

production. Batches of the product can be made as often as required. The machines can

be easily changed to produce a batch of a different product.

Mass productionis when hundreds of identical products are made, usually on a

production line. Mass production often involves the assembly of a number of sub-assemblies of individual components. Parts may be bought from other companies. There

is usually some automation of tasks (e.g. by using Computer Numerical Controlmiller)

and this enables a smaller number of workers to output more products.

Continuous flowproduction is when many thousands of identical products are made.

The difference between this and mass production is that the production line is kept

running 24 hours a day, seven days a week to maximize production and eliminate the

extra costs of starting and stopping the production process. The process is highly

automated and few workers are required

Moores Law

This is the observation that, over the history of computing hardware, the number of transistors

in a dense integrated circuit doubles approximately every two years resulting in the

miniaturization of integrated circuits.

Rapid Prototyping:

This is the production of a physical part, using three dimensional CAD.


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PCB Production:

1. Print circuit artwork on to acetate and cut circuit board to required size.

2. Remove the plastic layer from the circuit board and place in a UV Box with the

acetate stencil to develop the PCB image.

3. Rinse with water.

4. Develop in etching tank.

5. Drill and Sand

6. FLux

PCB Soldering:

Wave:

Reflow:

A sticky solder paste is used to attach SMT component to the board. The board is then

subjected to two stages of heat causing the paste to melt and solder the components to the

board.


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Logic Gates:

Flowchart Notation:


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Computer-aided design:

When a circuit has been finalised, a printed circuit board is usually designed and manufactured.

Specialist software can be used to plan where the tracks, pads, strain holes and mounting

holes will be on the PCB.

CAD software can also be used to design the structure or packaging of control systems.

Software can also be used for writing the program used in microcontrollers. It is written in

programme-editing software (Picaxe Programming Editor) before being downloaded onto the

chip.

Advantages and disadvantages of using CAD

Advantages

Can be more accurate than hand-drawn designs - it reduces human error.

You can save and edit ideas, which makes it easier and cheaper to modify your design as

you go along.

You can modify existing ideas, which saves time.Disadvantages

The software itself can be expensive so initial costs are high. There are free software

packages though.

Staff need to be trained how to use the software, which also adds to costs.

Requires a PC.

Computer-aided manufacture:

When a PCBlayout has been designed using CAD, the board can be produced or manufactured

using CAM.

Two examples of CAM are:-

3.

A design machined by a computer numeric control (CNC) miller, which removes all the

unwanted copper from the board.

4. A design layout printed on to acetate and transferred to a copper-clad board using

the photo transfer method. The unwanted copper is removed using acid.

Advantages and disadvantages of using CAM

Advantages

In large-scale production, the results are consistent (always the same).

Enables very high accuracy levels in large-scale production.

Usually speeds up production of low-volume products.

Disadvantages The software itself is expensive so initial costs are high.

Can be slower than traditional methods for one-off or low-volume production.

Staff need to be trained how to use the software and machinery, which adds to costs.


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Mechanisms:

Motion:

Levers:

Mechanical advantage = load effort

Velocity ratio = distance moved by effort distance moved by load


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Cams:

Gears:

Velocity ratio/Gear ratio = number or teeth on driven gear number of teeth on the driver gear

Output speed = input speed gear ratio

Pulleys

Velocity ratio = diameter of the driven pulley diameter of the driver pulley

Output speed = input speed velocity ratio

Output torque = input torque velocity ratio.


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Linkages:

Line bending

Line bending is used to make simple bends in a sheet of thermoplastic polymer. A simple

enclosure can be made from two U-shaped parts, attached together using a suitable adhesive.

Line bending involves heating the material along a line, using a heating element. The plastic

softens as it heats, allowing it to be bent. As the plastic cools it will retain its shape. A wooden

former is often used to ensure accurate bending.


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Vacuum forming

Vacuum forming is used to make many different products from thermoplastic sheets. These

include enclosures, packaging, helmets and baths.The sheet is heated to make it flexible, formed over a mould, and then cooled to become hard

again.

Step 1 - Plastic placed over mould

Step 2 - Plastic heated

Step 3 - Air in mould removed

The moulds used in vacuum forming have the following characteristics: They are often made from wood or medium density fibreboard (MDF).

They can be shaped by hand or using computer-controlled machines.

The sides of the mould must slope to allow the plastic product to be lifted off or pulled

out. This slope is called the draft angle. It should be between five and 10. If there was

no angle, the plastic product might stick into the mould.

The corners of the mould should have a small radius.

Any recesses must have small vent holes drilled in them to prevent trapped air stopping

the plastic sheet forming.

Vacuum forming can only be used to make shapes of simple profiles, as any overlaps would

cause the plastic to be stuck on to the mould.


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Injection moulding

Injection moulding is used to make a wide range of plastic products, from enclosures to model

construction kits, chairs and toys. The process is very fast and complicated shapes can be made

from both thermoplastic and thermosetting polymers.Injection moulding involves heating the polymer until it is liquid and then using pressure to

force it into a mould. Injection-moulded parts can often be identified by their sprue point, a

slight protrusion where the plastic was injected into the mould. They may also have a split

line visible if the sides of the mould did not fit together perfectly.

Laser cutting

Although laser cutting is a relatively new process, it is already widely used in all levels ofproduction. A computer-controlled laser beam burns through a sheet of material, such as thin

sheets of plastic, MDF or aluminium. It can cut simple 2D shapes that can be joined together to

make an enclosure.


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Electronic Components

Documents

DT WJEC Revision Notes