26-07-2014, 02:41 PM
COMPUTER AIDED PROCESS
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INTRODUCTION
Before introduction to the role of computer aided process planning (CAPP), it is
worthwhile to understand the role of process planning in the product cycle. Once the
design of the product has been evolved from customer’s views, its manufacturing
necessitates careful planning and scheduling of the various processes of manufacture. So
that, the product is made to right specifications and delivered at the right time at a
minimal cost. The cycle from concept to design, planning, production, quality control
and feedback to design goes on in which one can easily understand the crucial role of
planning. In job/batch manufacture, as an enormous amount of data is needed for
planning as well as other activities, data bases are required and the flow of information
should be fast for a high performance of the total manufacturing system
Computer-Aided Process Planning
Computer-aided process planning (CAPP) helps determine the processing steps required
to make a part after CAP has been used to define what is to be made. CAPP programs
develop a process plan or route sheet by following either a variant or a generative
approach. The variant approach uses a file of standard process plans to retrieve the best
plan in the file after reviewing the design. The plan can then be revised manually if it is
not totally appropriate. The generative approach to CAPP starts with the product design
specifications and can generate a detailed process plan complete with machine settings.
CAPP systems use design algorithms, a file of machine characteristics, and decision
logic to build the plans. Expert systems are based on decision rules and have been used
in some generative CAPP systems.
CAPP has recently emerged as the most critical link to integrated CAD/CAM system
into inter-organizational flow. Main focus is to optimize the system performance in a
SUMMARY
In the early 1970s, the function of process planning received very little attention. Today,
manufacturing environment has become more complex and competition has become
more intense. Hence, process planning has been accepted as critical to the success of
many companies. Process planning bridges the gap between design and manufacturing.
In addition, it has been acknowledged to be the link between CAD and CAM. As a result
process planning is recognized as a vital element in CIM environment.
This unit dealt with process planning where more focus was concentrated on CAPP. It
begins with the introduction of process planning and its various components. We
discussed and illustrated with examples the element of process planning, such as analysis
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Computer Aided
Process Planning
of part requirement; selection of the raw workpiece; determining manufacturing
operation and their sequences; selection of machine tools; selection of tools, jigs or
fixtures and inspection equipment; and determining machining condition and
manufacturing times (setup time, processing time and lead time). After that Computer
Aided Process Planning is discussed by explaining the reason why Computer Aided
Process Planning has recently received much attention both in industry and academia. It
follows by an overview of basic approaches for building Computer Aided Process
Planning system : variant and generative. It then discusses the basic component required
in a variant or generative system. A few existing knowledge based Computer Aided
Process Planning systems are reviewed. After that, principles of making decisions for
using either variant or generative approaches are discussed. Feature recognition in
Computer Aided Process Planning has been discussed with a brief review of part feature
recognition approaches. In this unit, we limit our exposition to the graph based approach
to feature recognition. And finally focuses are made on recent trends in Computer Aided
Process Planning.