A FEATURE AND KNOWLEDGE-BASED OBJECT-ORIENTED PROCESS PLANNING METHODOLOGY FOR THE MANUFACTURE OF PROGRESSIVE DIE PLATES

Abstract

A progressive die is a special purpose tool designed and custom-fabricated for producing large quantities of accurately formed, complex and interchangeable sheet metal components economically and rapidly. The degree of precision and complexity of the die components will vary considerably in relation to the dimensional tolerances of the sheet metal components. Many computer-aided design (CAD) and computer-aided manufacturing (CAM) systems have been developed to improve the effectiveness of the design and manufacture of progressive dies. These CAD/CAM systems, however, are not capable of generating detailed process planning information for the complete manufacturing cycle of progressive die plates. Such planning information is crucial to the down-stream manufacturing activities. In the precision metal machining industry, process planning can be described as the function which establishes the methodology and tools needed for the cost effective production of engineering components. Traditionally, process planning for the manufacture of progressive dies is a domain commonly associated with experienced tool makers, as the required skills and knowledge are highly specialised. In order to resolve the issues associated with manual process planning, including the shortage of skills and inconsistencies of the plans, a structured methodology has been specifically formalized in the research described in this thesis to automate and standardize the process planning function for the manufacture of progressive die plates. In essence, the planning methodology sets the priority for sequencing the different machining operations and heat-treatment processes often used in the manufacture of progressive die plates. This methodology and the related techniques, procedures and concepts are implemented in an experimental feature-based process planning system, called the Intelligence Knowledge-based Object-Oriented Process Planning (IKOOPP) system. The (IKOOPP) system has been imbued with a complete set of Planning knowledge for the sequencing of machining operations, together with the selection of suitable setups, machine tools, cutting tools and heat-treatment processes, for the manufacture of progressive die plates. A die assembly is designed using a variety of standardized components based on a commercial CAD/CAM system. A feature extractor has been developed to extract all the pertinent geometrical and functional attributes of the machining features from a model of a die plate. These attributes are used by the IKOOPP system to generate a process plan for the manufacture of the die plate. The process planning knowledge has been broadly classified into meta-knowledge and functional knowledge. The meta-knowledge directs the overall planning process within the IKOOPP system. The functional knowledge governs the selection of raw materials. Machine tools, cutting tools, setups, machining sequences, heat-treatment processes and machining parameters. Specialised knowledge of the functions of the machining features is also used effectively to deduce the engineering information which cannot be represented easily within the CAD system. Suitable representational techniques have been developed and merged together to represent the machining features, process planning knowledge and manufacturing resources. These techniques include the object-oriented schemes, production rules, procedures and manufacturing databases. They are integrated in a manner which will allow the relevant knowledge, information and data to be exchanged effectively.