Computer Aided Process Planning or CAPP

Every part or product that has to be manufactured in the machine shop of the manufacturing company has to undergo through a series of machining operations in a proper sequence. The manufacturing process planning involves determining proper sequence of manufacturing operations to be carried out so that part can be produced in the least possible time making the optimum use of the available resources. To make the proper sequence the operations are documented on a form known as the route sheet. In the route sheet there is a list of the production operations and the machine tools that can carry out these operations on the part or the assembly.

Apart from process planning the manufacturing supervisor has to determine the appropriate cutting conditions for the machining operations, ensuring that there is least wastage of the material. Then the supervisor also sets the appropriate time for each machining operations so that the part can be manufactured within the stipulated time ensuring the optimum productivity.

All the three tasks: process planning, determining cutting conditions, and setting the time standards are routine ones for the production engineer and it mostly involves the clerical content. Among the different companies and the industries there are lots of variations in the format of the route sheet and the details found on it.

The whole process of planning is done in different way in different companies. In some companies the machinists are merely given the drawing and asked to complete the job. In some cases the manufacturing engineering gives detailed list of the steps of the machining operations and also mentioning the work center on which the operation has to be carried out.

It is the duty of the manufacturing engineer within the company to write the process plans for the new part designs to be manufactured in the machine shop. The process planning task is usually too much dependent on the experience and the judgment of the engineer working in the production shop since years.

Until recently, the whole process planning tasks were being done manually. However, the individual engineers have their own opinions about what constitutes the best routing for the manufacture of a job. Due to this there are differences in the sequence of the machining operations developed by different planners. But now the computers are being used for manufacturing planning tasks. The use of computers for process planning enables removing a number of problems associated with the manual process planning.

The use of computers for process planning is called as Computer Aided Process Planning or simply CAPP. With CAPP the routine clerical tasks of the manufacturing engineers are reduced, so they can invest their time in more productive tasks. Further, with computers it becomes easier to generate production routings that are rational, and consistent without depending on the experience or the judgment of the individuals.

There are two approaches for computer aided planning process: retrieval type CAPP systems and generative CAPP systems. Both these systems have been described below.