IIT NewsSummer 2002
UPDATE
  Newsletter of Industrial Research & Consultancy Centre

 
FOCUS
Low Cost Automation

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

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

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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