Development of Information Technology Framework for the feature based Machining of Milling Parts using STEP-NC Compliant Standard ISO 14649

Abstract

World has turned into global village now-a-days, and same is the case with the manufacturing enterprises. Most of the manufacturing enterprises consists of production plants operating at different places around the world, and each consists of different machine tools of different makes. A large amount of data is required to be transferred between these facilities. The consistency and reliability of the information being transferred is ensured by the standards of digital communication. In case of mechanical parts, the standard data model is defined by ISO 10303, which has enabled the use of data in standard format throughout the manufacturing process chain. Taking this concept further at machine level, most of Computer Numerical Control (CNC) Machines are programmed in G & M Codes Language defined in ISO 6983. The Computer Aided Manufacturing (CAM) System takes the data from Computer Aided Design (CAD) System and generate G & M Codes based on ISO 6983 for manufacturing the part on CNC machine. The ISO 6983 has certain limitations. Firstly, it is not feature-based and so does not recognize the feature which is to be manufactured. It only considers the tool center point path with respect to machine axes and do not considers the machining process and part. Secondly, this standard defines the arrangement of program statements, but mostly leaves the semantics unclear. Thirdly, there are some vendor specific extensions that different vendors include in the language for their machine, which are not covered in the limited scope of ISO 6983. Due to this reason the part program written for one machine cannot be run directly on another vendor’s machine. A new data model for transfer of information between CAD/CAM systems has developed in ISO 14649, in accordance with ISO 10303. The limitations of ISO 6983 are addressed in ISO 14649 by using feature-based approach. It specifies machining processes rather than just stating the tool motion path. ISO 14649 not only focuses on manufacturing processes but also it provides multi-directional flow of data between all information technology systems integrated in a manufacturing enterprise, and thus facilitates Computer Aided Process Planning (CAPP) and Computer Integrated Manufacturing (CIM). Further, as it is object and featured oriented and not machine dependent axes motions, therefore it can be executed on different CNC Machine Tools without the need of post processing.