The assembly operation consists of the two basic activities of handling and insertion. If a product is to be assembled automatically then thought has to be given to the economics of these activities. The automatic feeding of simple parts is usually carried out using a vibratory bowl feeder. Components in bulk random orientation are placed into the feeder and the parts are presented to the workhead in an ordered manner. Difficult parts may be fed by special feeders, hoppers or by magazines. The insertion process is defined as being the action where one part is assembled to another part, or group of parts. High speed operations, where the same parts are inserted for long periods of time, are normally effected by standard pick-and place units. Difficult operations, involving the assembly of a number of different parts with different operations may require assembly robots. The flexibility of the robot is created by using computer programs to control the robot arm movements. The difference between a robot and a pick-and-place is that the path of the robot arm is not restricted by mechanical means, whereas pick-and-place units rely upon mechanical stops to determine the path they follow.
Division of labour
The division of labour is the process whereby one complex operation is
broken down into a number of simpler tasks. These single tasks are
carried out using a series of people, each doing one task. In this
manner, a complex task performed by one worker is replaced by a number
of workers operating in series. This allows operations to be carried
out simultaneously, instead of the single operator having to complete
one task before commencing another, different task. Unskilled workers
can then be used to carry out these simple operations and they soon
become efficient at the particular task.
An assembly method can be classified into one of six types, and most systems may contain a number of different methods.
The traditional form of assembly is manual and, for high volume
production, the workers are arranged on an assembly line. Other forms
of manual assembly include a single worker assembling a complete
product and groups of workers assembling a portion of the product.
When the range of products is more limited, a manual assisted method
can be used, whereby workers are assisted by mechanical devices, such
as parts feeders. The feeders present the parts to the assemblyworker
in an ordered manner. The assembly time is reduced by eliminating
the time taken to separate the parts from bulk random orientation.
The third form of assembly uses automatic indexing assembly
machines. A rotary or in-line machine has a number of
workstations with automatic feeders which supply components to
workheads for assembly of the part to the fixture, or part-built
assembly. The workstations are 'special-purpose' and are dedicated to
the assembly of one product only. Production volumes need to be high
for the economic justification of these machines. Component quality
must also be high to avoid excessive workstation downtime, caused by