STEP-NC and function blocks for interoperable manufacturing

Abstract

Interoperable manufacturing systems help manufacturing companies stay competitive in the environment of frequent and unpredictable market changes. An important part of a manufacturing system is computer numerically controlled (CNC) machine tools. Over the years, G-codes have been extensively used by CNC machine tools and are now considered as a bottleneck for making these machines adaptable and interoperable. Two new technologies emerged in recent years: Standard for the Exchange of Product data for Numerical Control (STEP-NC) and function blocks. The STEP-NC data model represents a common standard for NC programming, making the goal of a generic NC code generation facility a reality. Function blocks are an emerging IEC standard for distributed industrial processes and control systems. They can be used for CNC controls to encapsulate machining data, such as machining features and their needed algorithms. This paper introduces the above two new standards and the technologies that are developed based on the standards. The main body is devoted to analyze the standards from the functionality viewpoint. These functionalities include, bidirectional information flow in computer-aided design/computer-aided manufacturing, data sharing over the Internet, the use of feature-based machining concept, modularity and reusability, intelligent and autonomous CNC, and portability among resources. Some implementations are also presented to showcase how the standards are used to develop technologies for interoperable machining. Note to Practitioners-Modern computer numerically controlled (CNC) machine tools are limited in functions because their controllers rely on G-codes for communications. G-code is considered a "dumb" language as it only documents instructional and procedural data, leaving most of the design information behind. G-code programs are also hardware dependent, denying modern CNC machine tools desired interoperability and portability. In recent years, two new standards emerged, STEP-NC and function blocks. They may hold the key to empowering CNC machine tools with richer information which, in turn, gives CNC machine tools the ability to "think" intelligently and to be interoperable. This paper introduces these two standards, the technologies that have been developed based on the standards and some prototype systems using the standards and technologies. The intention is not to highlight any achieved research outcome. Instead, the focus is on informing the research and practical world about these new standards, analyzing them from the viewpoint of supporting interoperable CNC machine tools, and offering some futuristic views about these standards and technologies. While these standards are still in their infancy, research activities and prototype systems are already coming thick and fast. There seems to be a "healthy" mixture of participants working in the field. They range from the manufacturers of all systems related to the data interface (i.e., CAM systems, controls, and machine tools), to the users and academic institutions.