Engineering revision . . .
Learning objectives: o Be able to explain why standard electrical
and electronic parts are used
o Describe a wide range of electrical and
electronic components and their uses.
o Describe a range of pneumatic
components and their uses
o List a variety of standard mechanical parts
o List the 5 types of Engineering processes
o Describe the type of operation carried out
by each of the main Engineering
processes
Electrical and electronic components :
 Electrical components can be grouped according to
how they are used in a circuit
 It is easiest to understand these functions if we
think of a circuit as being a system.
 The main functions are; inputs, processes, outputs
and supporting parts.
INPUT
PROCESS
OUTPUT
Examples of components . . .
INPUT
SWITCH
PROCESS
OUTPUT
THERMISTER
FUSE
CAPACITOR
BUZZER
LAMP
LDR
DIODE
SUPPORTING
LED
RELAY
BATTERY
MOTOR
RESISTOR
CIRCUIT
TRANSISTOR
WIRE
INTERGRATED
SPEAKER
Examples of components . . .
INPUT
PROCESS
OUTPUT
SUPPORTING
SWITCH
THERMISTOR
LDR
INTERGRATED CICUIT
TRANSISTOR
LED
LAMP
BUZZER
SPEAKER
MOTOR
BATTERY
RESISTOR
FUSE
CAPACITOR
DIODE
RELAY
WIRE
SWITCH
THERMISTER
FUSE
CAPACITOR
BUZZER
LAMP
LDR
DIODE
LED
RELAY
BATTERY
MOTOR
RESISTOR
CIRCUIT
TRANSISTOR
WIRE
INTERGRATED
SPEAKER
Lesson task:
Look at the common electrical components.
Sketch each component symbol and explain the function of each
one.
COMPONENT
SYMBOL
USE
FUNCTION
SWITCH
(LATCHING)
SWITCH (PUSH TO
MAKE)
THERMISTOR
LDR
INPUT
Pneumatic, hydraulic and mechanical
components :





Pneumatic systems are powered by gas, normally air instead of electricity to carry out their
function
Hydraulic systems use liquid instead of electricity
Both types of system rely heavily on moving pressure from one place to another
The gases used in pneumatic systems can be compressed and the pressure this creates is
used to do work
Liquids DO NOT compress and are used in systems where much heavier work is required
The reason why these systems may be used in some applications instead of electrical:
-
It might not be safe to use electricity due to the risk of sparks or possible interactions with
other electrical equipment. E.g. a common use of pneumatic systems is to clamp tools, open
doors or move parts in electrically powered machine tools.
-
It might be easier to carry out the task needed by the direct force rather than converting
electricity to movement. E.g. a common use of hydraulic systems is to push the brake pads
in a car onto the brake disks.
Forming techniques:
There are 5 types of engineering processes:
o Shaping
o Forming
o Surface finishing
o Joining
o Assembling
Shaping . . .
Shaping involves pouring or forcing liquid
material into moulds. This involves
techniques such as casting and moulding.
Once this material has become solid it is
removed from the mould.
This is the only process that can turn
material into complex, three-dimensional
forms in a single operation.
Parts can often require some materials
removal after shaping. E.g. this can
include material that has been squeezed
into any gaps where a part of the mould
join together, which is known as ‘flash’.
Shaping . . .
Sand casting:
 http://www.technologystudent.com/equip1/alumin3.ht
m
Die casting
 http://www.bbc.co.uk/learningzone/clips/castingmetals-die-casting-and-sand-casting/901.html
Injection moulding
 http://www.youtube.com/watch?v=1WjM0it9jI&feature=related
 http://www.youtube.com/watch?v=eUthHS3MTdA
 http://www.technologystudent.com/equip1/inject1.htm
Injection moulding
Process description:
Diagram of process:
Forming . . .
Forming changes the shape or size of the
material, but normally does not affect
the overall volume of the material. This
is normally achieved by applying some
form of force to the material, such as
hammering, air pressure or a vacuum.
Some materials are easier to form if they
are heated prior to forming. However,
unlike shaping, the material does not
become liquid at any stage of the forming
process.
Forming . . .
Strip bending
http://www.technologystudent.com/jo
ints/desk17.htm
Vacuum forming
http://www.youtube.com/watch?v=NP
LWxxyIJcE&NR=1&feature=fvwp
http://www.technologystudent.com/e
quip1/vacform1.htm
Vacuum forming
Process description:
Diagram of process:
Surface finishing . . .
The involves modifying the surface of the
part in a useful way. The aim of finishing
is normally to improve one or more of
the properties of the part, such as its
appearance or its corrosion resistance.
Finishing processes includes applying
coatings, chemical treatments or
polishing.
The type of finishing process applied will
depend upon the materials that the parts
are made from the properties needed.
Finishing processes may be applied to
individual or assembled parts.
Surface finishing . . .
 Painting
 Plating
 Anodising
 Galvanising
 Etching
 Polishing
Painting . . .
Can be used to provide a decorative and corrosion
resistant coating for metal surfaces. It is the easiest
and cheapest way of coating an item. Paints
consist of 3 components:
o PIGMENT – this is what provides the paint with
its colour
o VEHICLE – this is the part that has to form a film
when the paint dries and sticks to the surface
o SOLVENT – this controls how easy the paint is to
apply. It evaporates as the paint sets.
All paints can be applied by brushing, spraying and
dipping.
Plating . . .
Uses a process called electrolysis to coat the
surface of the metal with a thin layer of
material.
This means that the part to be coated is put in
a bath or tank containing a solution of
chemical salts and an anode. The anode is a
piece of the metal that will be used in the
coating.
An electric current is passes through the part,
the solution and the anode. This causes a thin
layer of metal to slowly build up on the part.
At the same time, the anode gradually
dissolves away.
Used to apply coatings of; nickel, zinc, copper
and tin.
Anodising . . .
This is a plating process which is most often
used on aluminium.
It involves electrolysis in an acid solution.
It provides a durable, corrosion resistant
finish.
Colour can be added to tint the aluminium for
decorative purposes.
Anodising is used to make the dielectric films
that are used in electrolytic capacitors.
Anodised titanium is used for dental implants.
Galvanising . . .
This process involves dipping metal into a bath
of molten zinc.
The liquid zinc sticks to the steel and cools to
form the coating.
It is normally used to mild steel.
The zinc provides good corrosion resistance,
although the appearance of the coated part is
not attractive.
Often used for; metal dustbins, buckets and
road signs.
Etching . . .
During etching, selected areas of the surface
are dissolved by chemical action.
It is commonly used in the production of
printed circuit boards (PCB’s), where the tracks
needed for the electricity to pass through
when the circuit is made are protected from
the etching solution.
Etching is also used to provide decorative
finishes on metals and on ceramic items such
as glass. The areas that the chemicals can
touch and the amount of time that the
chemicals can contact part must be carefully
controlled to get the desired effect.
Joining and assembling . . .
Joining and assembling involves attaching
or putting the parts together. This might
be achieved by bonding parts so that
they are permanently attached or by
using mechanical fastenings to hold them
together.
The joining processes used will normally
be specified in the design, as it can have
a significant effort on the performance of
the product.
Joining and assembling . . .
Permanent:
- Welding
- Brazing + soldering
- Riveting
Temporary:
- Threaded fastenings such as; nuts, bolts and
screws
Adhesives:
- Epoxy resin
- Acrylic cement
- Polyvinyl acetate (PVA)
Useful websites . . .
• http://skateboardproduction.weebly.com/ind
ex.html