Object-oriented technology may provide a powerful representation and classification tools for a virtual flexible manufacturing cell. It may also provide a common platform for the information sharing between sub-modules, and provide a richer way to store/retrieve/modify information, knowledge and models and reuse them. In the context of an object oriented approach, a model is simply an abstraction, or a representation of an objects or process.
VFMC requires a robust information infrastructure that comprises rich information models for products, processes and production systems. As shown in Fig. 2, three models, that is product model, facility model, and process model, are developed for virtual flexible manufacturing cells.
A product model is a generic model used for representing all types of artifacts, which appear in the process of manufacturing. It represents target products, which include conceptual shape information as well as analysis module for a specification, productivity, and strength. A facility model contains information about machines consisted of a virtual flexible manufacturing cell. By using the model, innovative tooling and methods can be evaluated without the cost of physical machine prototypes and fixture mock-ups. A process model is used for representing all the physical processes that are required for representing product behavior and manufacturing processes.
3.1 Product model
A product model holds the process and product knowledge to ensure the correct fabrication of the product with sufficient quality. It acts as an information server to the other models in the VFMC. It also provides consistent and up-to-date information on the product lifecycle, user requirements, design, and process plan and bill of material. An instance of Class Part provides detailed information about a part to be fabricated in VFMC. Sub-classes like Process-Plan, BOM, and NcCode, are aggregated into the class Part. Classes Process-Plan and BOM manipulate information and data associated with process plans and bill of materials, respectively. Class NcCode deals with NC programs, which interacts with CAD/CAM systems. With incorporation with the facility model, this developed NC programs can be verified and checked for collisions and interference with any work-piece or tooling in the fixture. This can avoid costly machine crashes and reduce risk during initial equipment installation and produce launch. Furthermore, productivity can be improved by avoiding nonproductive time for program prove out on the machine tool and by using the simulation environment to train operators of new machines.
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