I originally presented this article, "The Design of Hybrid Flexible Assembly Systems", as a guest speaker at the 6th International Conference on Assembly Automation ...
There is a requirement for a special kind of system to assemble
products required in modest volumes with a degree of variety. A
system which is as cost effective and efficient as hard automation,
whilst providing the flexibility of manual assembly, is called a
flexible assembly system. Within such a system, certain product parts
may be required at a different rate to other parts. Some operations may
require the flexibility and dexterity of a robot, or even manual
labour. The resultant system would be a hybrid of many methods of
assembly. This article recommends a technique to be used for the design
of such a system, with the aid of a case study.
The factory cost of a product is the addition of the manufacturing cost
(e.g. casting, moulding, turning) and the assembly cost (e.g. manual,
automatic, robotic). Industrial engineers continually seek new
methods to reduce the factory cost of products. The current trend of
exploiting cheap labour in developing nations, through “offshoring”
creates a challenge for domestic manufacturers in the developed
nations. Between 40 and 60 percent of the factory cost for many
products is associated with the labour content. The majority of this
cost is incurred during assembly. There are three reasons for this
uneven split between labour costs in manufacturing and assembly.
(i) Manufacturing operations are usually done by, or with the aid of, a
machine, i.e. turning, milling, drilling, etc. The manufacturing
systems designer does not have the wide choice of the assembly systems
designer because some degree of mechanisation must be used. It is then
a logical extension to further automate the manufacturing process to
reduce labour costs.
(ii) New processes have been developed which eliminate many
manufacturing operations. Powder metallurgy is an example of such a
(iii) Most products are designed to be assembled manually. This
often means that components are of such a design that they cannot be
handled by automatic feeders. Additionally, many assembly
insertion operations are too complex to be automated.
The assembly process is one of the last production processes to be
successfully automated by theindustrial engineer. However, as much of
the factory cost of a product is incurred during assembly, it is this
area where great productivity improvements can be made. The design of
the assembly system should be undertaken with due consideration of the
design of the manufacturing system and of the design of the product.
The design of the assembly system, manufacturing system and product
should be considered integrally. These three components, when combined,
should create a product having the lowest factory cost at the desired
level of quality. The design of a product and it’s associated
production system is an iterative process, whereby product design
features dictate the design of the production system and the
capabilities of the production system determine the product design. The
extent to which these actions can be carried out is only limited by the
commitment of a manufacturer to a particular production system and