Introduction of CAPP Techniques

"Fully Automated Factory" or in other words "unmanned factory" has been a major and long-term goal of both industry and academia for a long time, although some authorities claim that it is impossible to achieve. CAD and CAM are two of the most important activities to be amalgamated in a typical automated environment. Because of developments in numerically controlled equipment, computer technology, robots and computer controlled automation in CAM and CAD systems, several manual skills have been automated, therefore resulting in reduce of lead times, enhancement in productivity and enhance in manufacturing accuracy. Though, the full integration of CAM & CAD systems in industry has not yet been attained. CAPP is one of the most significant obstacles to be overcome in the automation of process planning activities; it forms a bridge between CAD and CAM. The CAPP was first proposed by Niebel. Schenck supported the CAPP idea of Niebel by his Ph.D dissertation at Purdue University in year of 1996. Due to the limitation of computer hardware and software, the CAPP had not been feasible until the early 1980s. CAPP is very inclusive and basically consists of the determination of processes and parameters required to convert a blank into a finished product. The key elements of process planning include; material selection, operation selection, machine tool selection, operation sequencing, cutting tool selection, set-up selection, etc. Automated process planning brings about following advantages:

• Decrease in process planning time
• Decline in the needed skill of the process planner
• Drop in costs due to efficient use of resources
• Improved productivity and process rationalisation
• Production of accurate and consistent process plans
• Maximisation of just-in-time performance

Nowadays, it has been recognised that Computer Aided Process Planning is the key system promoting the integration of CAM and CAD systems. It has been seen as the only tool for eliminating the slash between CAD/CAM.

Process planning as the link among CAM and CAD, actually translates the design language into the manufacturing language. There have been a large number of efforts and studies to attain the major goal via CAPP; to effectively integrate the design and manufacturing, providing the standardisation and automation of the process planning function. Although, it is worth noticing that the industrial utilize and applications of the developed systems are quite restricted. One of the major reasons behind this lack of industrial use is that the process planning is a complexes and divergent task including several sub-activities from the interpretation of the product data to the tool path planning and CNC part program generation, and among these sub-activities there are several highly complex and ill-defined relationships. Another purpose may be the difference between the assumed conditions and actual conditions on the shop floor, or the presence of unexpected disturbances, or continuously changing demand, or improved technology. The performance and applicability of the CAPP systems can be improved by including a higher number of the actual manufacturing variables and by providing adaptive structure to the system.