Interpreting module and coordinate problem for CNC based on STEP-NC interface

Aiming at the data model and programming character of object oriented of STEP-NC, with design thinking of software module applied, an interpreting module including four sub-modules is built. 1, Inputting sub-module is responsible for parsing STEP-NC program, and a special data structure is designed to store the entity information of program line. 2, Recognizing sub-module can recognize all kinds of entities in the machining program, and a fixed recognizing order is proposed to guarantee the accurate result. 3, Modeling sub-module establishes corresponding C++ class model by entity mapping according to entity type. 4, Planning sub-module plans the tool path according to the class model parameters, and its running process is explained. A complicated problem involved in path planning is coordinate transformation. The hierarchy frame of coordinate of STEP-NC is summarized and the coordinate reference principle is elaborated. By visual tool path in a simulation system for 3-D milling machining based on STEP-NC, the path planning is proved to be right. At last the interpreting module is planted into an open CNC and confirmed to be valid and correct by real machining experiment.