Aims of this work
In order to be competitive, modern products must be designed with a view to production methods in
which a production system should to be designed in a cost-effective way and the system is able to operate
at optimal or near-optimal conditions. Nevertheless, design of a production system can be a complex
process and any small change of the system design often makes a significant impact on the overall system
performance. In the real-world industry, implementation of the entire production system is often very
expensive and the cost of ‘getting it wrong’ can be very high. For these reasons, both system and product
designers need to work together to ensure a ‘right first time’ scenario. Virtual prototyping techniques
offer a potential solution to the major difficulties involved in design, analysis and performance evaluation
of a product and a production system providing a fast delivery of alternative solutions at a minimum of
cost. Nowadays, virtual prototyping techniques are commonly used in manufacturing sectors involving
some form of computer-aided design and modelling simulation activities.
Assignment & Tasks
This assignment is based on a case study of assembling loudspeakers on a production line that needs to
be investigated. A loudspeaker manufacturer has just upgraded its loudspeaker design by incorporating
some forged parts with improved magnetic characteristics for the unit, which has additional benefits of
reduced part count and part features to facilitate automatic feeding as well as ease of manual assembly.
Figure 1 shows the basic structure of a loudspeaker and Figure 2 illustrates what is known as the motor
unit assembly together with the voice coil. Figure 3 shows a cross-section through a typical loudspeaker.
The assembly of an entire loudspeaker is illustrated in Figure 4 and 5, respectively. The parts in the whole
assembly can be grouped into two different types namely:
dust cap, the diaphragm, the spider and the coil
pole piece, the magnet and the top plate together with the frame
The proposed manufacturing facilities should as far as possible incorporate automation, however, it is still
anticipated that some of the ‘soft’ parts may be assembled manually. The aim is to produce one
loudspeaker every 20s over an 8hr working day and a 5-day week (1440 units/day, 7200 units/week). The
speakers can be sold at £5/unit, giving a potential turnover of £36000/week and £1800000/year.
After an initial investigation of the system, data collection and analysis, the following system parameters
have been identified and determined:
Conveyors will be used and it may be 5, 10, 15 or 20 m long.
Each frame arrives randomly and is loaded in position (manually) in NegExp 18s.
Each pole plate can be fed/assembled in LogNormal 17s, STD: 5-15%.
The magnet can be fed/assembled in LogNormal 19s, STD: 5-15%.
The top plate can be fed/assembled between 15-18s in a uniform distribution.
Manual assembly of the spider and coil by a worker takes a time of 35-45s in a uniform
Assembly of the diaphragm takes an average time of 18s.
Manual assembly of the dust cap takes an average time of 16s.
At the magnetisation station: 20s.
At the automated test machine (ATM): 10s.
Fork-lift trucks may be used at the end of the production line and it may travel at 2m/s.