Systems and procedures
An electronics product can be thought of as a system with inputs, processes and outputs. The most common method of
manufacturing electronic products is the batch method - though one-off production and continuous-flow production are also
important.
ICT is used extensively in electronics manufacturing. The use of machines that are controlled by computers is called computer-
aided manufacture or CAM.
Systems in electronics
Electronics systems diagrams are used to show how the parts of a product work together. Many electronic products are made
up of a number of standard system circuits (circuits that are common to many different products), such as sensors, amplifiers,
timers, counters and output devices.
System diagrams usually take the form of a block diagram in which each part of the electronic system is represented by an
input, a process or an output.
The block diagrams below shows two types of system.
" The open-loop system has no feedback mechanism, so the accuracy depends on how well the system was set up
before hand.
" Closed-loop electronic systems use sensors to provide feedback. This means that if the output is not satisfactory, the
inputs or processes can be altered.
Production systems
There are four basic types of production system used in electronics - each one using different types of machine and with
different levels of automation. Which system is used depends generally on how many identical products are to be produced,
and how continuous the production is to be.
One-off or jobbing production
This is used to produce very small amounts or specialised electronic products. This might mean producing a single piece of
switch gear for a factory machine. Workers in this type of industry need to be highly skilled in a range of different areas and
able to work on a number of aspects of the project.
Batch production
This is the most common type of production in the electronics industry. It involves making a set number of exactly the same
product. Some batches will be small, others could be thousands. Batch production might be used to make PCBs for aircraft
controls, for example, or control panels for central-heating boilers.In batch production the operation is sub-divided into a
number of separate stages, with each stage being completed by different (often computer-controlled) machines. The stages in
an PCB batch production process might be:
" making the PCB
" drilling the holes
" populating the board with components
" soldering the components in place
" checking the board, and mounting it into the product
Mass or in-line production
This is used when very many identical products are required, such as
electronic circuits for cars, washing machines and fridges. The products are
assembled as they flow along a production line. The operators tend to be
semi-skilled.
In-line production plants are very expensive to set up and thousands of
products have to be sold to off-set the capital costs. Production is often
difficult to plan and breakdowns are costly.
Printed circuit board being checked after manufacture
Continuous-flow production
This is where production is heavily automated and runs 24 hours per day. Continuous-flow production is used in oil refining and
chemical processing. A considerable amount of electronic control is used in the running and monitoring of these plants.
Computer-aided manufacturing (CAM)
CAM is essentially the use of automated machines that are controlled by computers. Some of the advantages of using
computer-aided manufacturing are that
" machines can be quickly reprogrammed for each new batch of products
" consistent quality can be maintained
" specifications can be transmitted quickly from design to manufacturing, and from one machine to another
" machines can work continuously for long periods
" work can be carried out in conditions which would be hazardous to humans
Computer numerical control
When computers are used to carry out bespoke precision tasks, such as soldering circuit boards, this is called computer
numerical control or CNC. CNC machines can be programmed and operated from computers or other microprocessor systems
- either directly using a keyboard or keypad, or indirectly by means of disks, smart cards or other removable media.
In electronics CNC machines are used - among other applications - to 'populate' PCBs and solder the components in place.