Seminar On Computer Aided Process Planning (CAPP) Report Download
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.
– 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.
• CAPP is usually considered to be part of CAM, however this results CAM as stand alone system. • The experience of manufacturing of different engineers, who are likely to retire, can be made available in future by CAPP.
• 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.
The variant CAPP method
In variant CAPP approach, a process plan for a new part is created by recalling, identifying and retrieving an existing plan for a similar part and making necessary modifications for the new part. Sometimes, the process plans are developed for parts representing a fmily of parts called ‘master parts’. The similiarities in design attributes and manufacturing methods are exploited for the purpose of formation of part families. A number of methods have been developed for part family formation using coding and classification schemes of group technology (GT), similiarity-coefficient based algorithms and mathematical programming models.
The generative CAPP method
The next stage of evolution is towards generative CAPP. In the generative CAPP, process plans are generated by means of decision logic, formulas, technology algorithms and geometry based data to perform uniquely many processing decisions for converting part from raw material to finished state. There are two major components of generative CAPP; a geometry based coding scheme and process knowledge in form of decision logic data. The geometry based coding scheme defines all geometric features for process related surfaces together with feature dimensions, locations, tolerances and the surface finish desired on the features. The level of detail is much greater in a generative system than a variant system. For example, details such as rough and finished states of the parts and process capability of machine tools to transform these parts to the desired states are provided. Process knowledge in form of in the form of decision logic and data matches the part geometry requirements with the manufacturing capabilities using knowledge base. It includes selection of processes, machine tools, jigs or fixtures, tools, inspection equipments and sequencing operations. Development of manufacturing knowledge base is backbone of generative CAPP. The tools that are widely used in development of this database are flow-charts, decision tables, decision trees, iterative algorithms, concept of unit machined surfaces, pattern recognition techniques and artificial intelligence techniques such as expert system shells.
Advantages of CAPP and future trends
CAPP has some important advantages over manual process planning which includes;
• Reduced process planning and production lead-times
• Faster response to engineering changes in the product
• Greater process plan accuracy and consistency
• Inclusion of up-to-date information in a central database
• Improved cost estimating procedures and fewer calculation errors
• More complete and detailed process plans
• Improved production scheduling and capacity utilization
• Improved ability to introduce new manufacturing technology and rapidly update process plans to utilize the improved technology