As CAPP becomes more accepted in the factory environment, it will become necessary to integrate it with other functions. According to Ham[1988, 89] the advantages of such a development would be,

• improved efficiency in the information flow,

• improved quality of the process planning,

• reduction of the human errors,

• functional integration of process planning and scheduling, enabling a quick search for alternative solutions for optimization in the use of equipment and production control, and,

• flexible use of the different functions.

Ham [1988, 89] also asserts that there are certain key elements to a successful implementation of such a planner,

• a uniform product description based on proper features,

• the use of different modules for different functions,

• the use of a uniform user interface for each module,

• the use of a uniform data base for each module,

• the possibility of facilitating user interaction at the request of the operator.

Finally Ham [1988, 89] describes the issues involved in integrating CAPP with the related manufacturing functions.

• Planning Knowledge - A mixture of physical properties, and knowledge heuristics.

• Planning Activities - Must be integrated with Production Planning, and with Operation Planning, including physical process models.

• Planning Techniques - A collection of many process planning techniques (like Group Technology, Rules, etc.) must be used to avoid problems with each, and find the best plan possible.

• Planning Constraints - Technological, and other constraints, should be considered during planning, not simply used after planning to eliminate plans.

• Planning Feedback - Information which results from previous process plans must be used to issue new plans, and avoid similar mistakes in the future.

Some work has been done by various authors to address integrating CAPP with PPC. For example, Ruf and Jablonski [1990] discuss their system called FIPS. The system contains three modules, FREDOS (Feature Recognition, Extraction, Decomposition, and Organization System), SSM (Static System Manager), and DRS (Dynamic Resource Scheduler). Essentially FREDOS will identify the machinable features in the part. The SSM will then assign all possible combinations of machines to the process plan. The DRS module will dynamically schedule the jobs into various machines, depending upon the current status of all machines. Although this system is for a limited domain, it displays the important concept of delaying resource assignment until required.

The CAM-I group began developing an interface specification for connecting CAPP to their factory management programs [a section by Sack, in Nolan, 1989]. The project began in 1986, at the UTRC at MIT, where they defined and reconciled terms, and developed a conceptual view of the standard database structure. They produced a Process Plan data Interface Specification (PPIS), which indicated interface subroutines used by the various computer programs. The diagram in Figure 1.21 PPIS Interface Between CAPP and PPC shows how their system is used to integrate XPS-2 and a factory control system called MADEMA.

Other work has also been done by other groups on the general nature of integrated scheduling and CAPP. ElMaraghy [1992] examines bridging the data and functional gaps. Feedback of information about the resources was discussed by ElMaraghy, as well as Krause et. al. [1991] and Chryssolouris et. al. [1984].


Figure 1.21 PPIS Interface Between CAPP and PPC