Summary of CAPP
Computer-aided process planning (CAPP) is a comparatively new technology that has been developed to enhance the accuracy and productivity of the overall manufacturing planning effort. In this unit we introduced you the CAPP system.
CAPP is a highly effective technology for discrete manufacturing along a significant number of products and process steps. Rapid strides are being made to build up generative planning capabilities and incorporate CAPP into a computer-integrated manufacturing architecture. The initial step is the implementation of GT of FT classification and coding. Commercially available software tools presently exist to support with minimal risk and cost. Effective use of these tools may improve a manufacturer's competitive advantage.
One of the most significant steps in converting a design concept into a manufactured product is process planning. The necessity of that task is the building of a complete package of information on how to perform the manufacturing process, which can include work instructions for the shop floor, a quality control plan, a bill of material, tool planning, and so on. Also, there might be links to other manufacturing systems such like material requirements planning (MRP), time standards, product data management (PDM), engineering and manufacturing change control, shop floor control and data collection systems. In most of the cases, this initial package of information finally determines the final cost and quality of the product.
Traditionally, manufacturing engineers generate the essential process planning documents from scratch by using manual techniques. That need the retrieval and manipulation of a great deal of information from several sources including established standards, machinability data, tooling inventories, machine capabilities stock availability and hopefully, current practice. The resulting process plan was after that manifest in the form of printed text, drawings and lists.
The introduction of computers into manufacturing has surely made the planning function more efficient, however there are additional advantages. For one, computers may readily perform vast numbers of comparisons and, thus, many more alternative plans might be explored than would be practical in a manual setup. Also, the application of computers might bring greater uniformity to process planning. Ask ten engineers to build up a process plan for the same part, and you will possibly finish up with ten different plans. Not only does this mean some plans shall be better than others, but also that in essence similar jobs planned at different times shall be done differently. Though, with the comparative capabilities brought about by computer-aided process planning (CAPP), it becomes simple to answer the questions: Which plan best utilises the facility's capabilities? Which can be used for estimating future work? Which is best for shop loading and scheduling? And most significant, which plan reflects the best practice depend on past experience?
While CAPP might indeed answer these questions, to be of optimum value, specifically in larger manufacturing facilities, companies should carefully consider its implementation and integration with other systems. Here are some factors to think about if CAPP is to attain its potential.
CAPP got it's begin with Group Technology (GT), which was touted like a solution to manufacturing in an environment of smaller lots and shorter product life cycles. The underlying principle of GT is comparatively simple: Use a well-structured coding and classification system to identify similar components and processes. Then once "families of parts" are identified, they can be manufactured with standardised process plans.
Early CAPP systems were based on this common principle, and still are, though now there are basically two approaches to how systems work -generative and variant. In the variant approach, a set of standard process plans is established for all of the parts families recognized thought GT. Then when a new plan is needed, an applicable standard plan is retrieved and edited to suit the particular requirements of the new part.
In the generative approach, an attempt is made to synthesise every individual part using suitable algorithms that define the several technological decisions that should be made in the course of manufacturing. In an actually generative system, the sequence of operations in addition to all of the process parameters would be established automatically, without reference to prior plans. The expenses of setting up such a system are so high, though, that so-called generative process planning systems have been developed only for particular operations - selection of feeds and speeds, for instance, or for uniform families of similar parts.
Although some early CAPP systems contained elaborate classification and retrieval capabilities, coding all of the parts in a typical manufacturing environment proved to be unrealistic. It was just too tedious, time-consuming and costly. And in time, many of these systems were utilized primarily as work processors with some retrieval of standard texts. On the other hand, this was a great improvement over the old ways of paper-driven process planning. It just lacked the sophisticated retrieval and modification capabilities of a modern CAPP system.
CAPP is the link among CAD and CAM system. The CAPP system consists of several modules ranging from feature extraction module to intermediate surface generation module. Computer aided process planning systems decrease process planning times, improve consistency; enhance productivity, etc. when compared to the manual process planning systems.