2005

Sääski, Juha; Salonen, Tapio; Paro, Jukka

Modern manufacturing enterprises are built from facilities spread around the globe, which contain equipment from hundreds of different manufacturers. Immense volumes of product information must be transferred between the various facilities and machines. Today's digital communications standards have solved the problem of reliably transferring information across global networks. For mechanical parts, the description of product data has been standardized by ISO 10303 (STEP). This leads to the possibility of using standard data throughout the entire process chain in the manufacturing enterprise. Barriers to realizing this principle are the data formats used at the machine level. Most computer numerical control (CNC) machines are programmed in the ISO 6983 "G-code" language. Programs are typically generated by computer-aided manufacturing (CAM) systems that use computer-aided design (CAD) information. However, "G-code" limits program portability for three reasons. First, the language focuses on programming the tool centre path with respect to machine axes, rather than the machining process with respect to the part. Second, the standard defines the syntax of program statements, but in most cases leaves the semantics ambiguous. Third, vendors usually supplement the language with extensions that are not covered in the limited scope of "G-code". The replacement for G-code is so-called "STEP-NC", the name STEP-NC meaning the STEP standard extended for NC. STEP-NC is a new model of data transfer between CAD/CAM systems and CNC machines. It remedies the shortcomings of "G-code" by specifying machining processes rather than machine tool motion, using the concept of workingsteps. Workingsteps correspond to high-level machining features and associated process parameters. CNCs are responsible for translating workingsteps to axis motion and tool operation.