In general, since many
alternatives are possible, an in-depth study of the existing
system and the developer’s ability to visualize the modifications
for making the final automation easier are crucial elements in the
development process. These can make the subsequent system
implementation much easier. The third stage which involves
conceptual design/development calls for the ingenuity on the part
of the designer in evolving an elegant solution. A wide variety
of systems (mechanical, hydraulic, pneumatic, electrical and
electronics) are available for deployment in LCA systems. However,
each has its own advantages as well as limitations. For
uncomplicated situations, one can build a simple LCA device using
any of the above systems, through a rapid techno-economic
evaluation. However, in most of the practical applications, hybrid
systems are used since that can allow use of the advantages of
different devices, while simultaneously minimizing individual
disadvantages. During all three
development stages, intensive interaction between the people
working in the plant area chosen for LCA application, and the
designer of the LCA system is very essential. Indeed the success
or failure of LCA, during implementation, is highly influenced by
the thoroughness of preparation during these three stages. In the
experience of the present author, who has been involved with LCA
R&D for more than twenty fiveyears, for successful implementation,
the LCA expert needs to conceptualize a viable solution using
appropriate technologies, while paying heed to the twin
constraining parameters: ease of maintenance and overall economic
viability of the approach. Typically, the well-known techniques of
industrial engineering like Work Sampling, Pre-determined Motion
and Time Studies (PMTS), Developing Better Method (DBM) etc.,
coupled with the principles of "Design for Automation," can be
very useful in implementation.
LCA System Synthesis and
Development As shown in Fig. 1,
the designer should proceed in a systematic manner for developing
LCA systems. The system can be made well-integrated through
emphasis on the guiding principles of standardization, simplicity,
reusability, flexibility and maintainability. During the
cost-benefit analysis, long term benefits (like skill upgradation
of workers, more job satisfaction, safety, fatigue reduction,
reduction in % rejection, betterment of quality etc.) are to be
given due consideration. At the system
implementation stage, the integration of existing equipment,
tools, and workmen skills, and troubleshooting will consume
productive time. Thus, active and co-operative participation of
the workforce is very necessary to succeed. A Productivity
Assessment, after the system has reached "stable conditions", will
show what has been achieved. At this stage it is usually possible
to estimate the payback period, which, as noted earlier should not
be more than a few months in most cases. After stable operation
for sometime, further productivity enhancement is possible through
system upgradation.
Technologies Used for LCA
As we indicated earlier, LCA systems are basically mechanical,
pneumatic, hydraulic, electrical, electronic in nature. Hybrids
are
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more often used where the
above technologies are combined into electro-mechanical, electro-
pneumatic, pneumo-hydraulic and other
forms.We review
here the above technologies very briefly.
Mechanical systems These are generally rugged, simple and cheap.
They are made up of elements like cams, gears, mechanisms with
linkages, indexing devices, feeding devices etc. Cams are profiles
on a rotating shaft. A follower moves according to the profile of
the cam which converts the uniform rotary motion of cam shaft to
linear or angular motion with a variable speed and displacement.
The master camshaft controls the entire cycle of operations. The
cams are so designed and aligned that all the operations are
performed in the desired sequence for one full rotation of the cam
shaft. The time taken for one rotation of the master cam shaft is
the cycle time to produce the component. The operator has to only
load a long bar (raw material) after which the machine will go on
producing the parts till the raw material is finished. This also
means that one operator can operate more than one machine
simultaneously, thereby significantly reducing the cost of labour
per component. If
instead of feeding a long bar, discrete small components are to be
fed at a pre-set rate, for processing, a vibratory feeder bowl
feeds the parts one by one after orienting it in the desired
fashion, at the first work carrier. The work carriers are mounted
on a rotary indexing table. As the part get indexed from first
position to successive positions, some operation is carried out at
each position in a pre-set sequence. Once it reaches the last
position, all required operations would have been completed and
the component gets unloaded with available mechanical elements. In
this manner automation of very complicated operations are
possible. Pneumatic Systems
These operate using compressed air as the activating power source.
Usually the pressure used is in the range of 4 to 8 bar. Tyipcally
compressed air facility is available through piping. The pipe
running through the shop floor will have a number of tapping
points to which the LCA device can be connected.
Fig.2 Spring Disentangler and Feeder
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A typical pneumatic circuit
is shown in Fig. 2. This is a device, which helps in dis-entangling
springs, and feeding them one by one. As every automation engineer
knows, this is one of the toughest problems in automation. The
system here is very simple and has no moving parts. Pneumatic
circuits are extremely popular for LCA applications due to their
low cost, ease of fabrication safety in operation.
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