18-12-2012, 05:13 PM
Computer Aided Process Planning
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Computer Aided Process Planning (CAPP)
…..Process planning with the aid of computer
• Process planning is concerned with the preparation of route sheets that
list the sequence of operations and work centers require to produce the
product and its components.
• Manufacturing firms try to automate the task of process planning using
CAPP systems due to many limitations of manual process planning.
These includes:
– Tied to personal experience
– and knowledge of planner of production facilities, equipment, their
capabilities, process and tooling. This results in inconsistent plans.
– Manual process planning is time consuming and slow.
– Slow in responding to changes in product design and production.
• The experience of manufacturing of different engineers, who are likely
to retire, can be made available in future by CAPP.
• CAPP is usually considered to be part of CAM, however this results CAM
as stand alone system.
• Synergy of CAM can be achieved by integrating it with CAD system and
CAPP acts as a connection between the two.
• Readymade CAPP systems are available today to prepare route sheets.
Benefits derived from CAPP
• Process rationalization and standardization
• Increased productivity of process planners
• Reduced lead time for process planning
• Improved legibility
• Incorporation of other application programs
Design approaches of CAPP systems
Retrieval CAPP systems/ Variant CAPP
– This has evolved out of the traditional manual process planning
method. A process plan for a new part is created by identifying and
retrieving an existing plan for a similar part, followed by the
necessary modifications to adapt it to the new part.
– It is based on GT principles, i.e., part classification and coding. These
coding allow the CAPP system to select a baseline process plan for
the part family and accomplish about 90% of the planning work. The
planner adds the remaining 10% of the planning by modifying the
baseline plan.
– If the code of the part does not match with the codes stored in the
database, a new process plan must be generated manually and then
entered into database to create a new baseline process plan for
future use.
Advantages and limitations of Variant CAPP
– Investment in hardware and software is not much.
– The system offers a shorter development time and lower manpower
consumption to develop process plan.
– The system is very reliable and reasonable in real production
environments for small and medium size companies.
– Quality of process plan depends on knowledge and background of
process planner.