Research On Interpreting Module And Networked Sharing Of Machining Data Based On STEP-NC

STEP-NC is a new data interface, proposed recently for modern Computer Numerical Control (CNC), to replace G-codes. With STEP-NC having extended STEP into NC domain, CAD, CAM and CNC systems may be connected seamlessly. Undoubtedly this will facilitate the data exchange or sharing between different systems and is vital to realizing networked manufacturing mode. However, ISO10303-21 file format adopted by STEP-NC isn't suitede to apply on Interent. So new file format is needed to express the machining information. In the background, related technologies on realization of CNC based on STEP-NC and its data sharing based on Internet are studied.The primary problem to realize STEP-NC-based CNC is interpreting. STEP-NC machining program is a text file coded based on ISO10303-21 standard. It covers feature and geometry information, technology information, etc, taking object-oriented programming thinking. According to the character and analysis to function of interpreting module, the frame of interpreting module is proposed: inputtng sub-module, modelling sub-module and path planning sub-module. Inputting sub-module is used to parse machining program and save it by special data structure. A corresponding machining data model mapped by program is produced by modeling sub-module. Path planning sub-module is responsible for outputting path list, which is built according to geometry and technology information in program. Design principle and key technologies of all sub-modules are elaborated.To verify the correctness of interpreting module, a 3-D simulation system for milling process is developed. It can accept path informations produced by interpreting module and simulate real machining process. The structure frame of simulation syetem is introduced, particularly the building of data model of workpiece and material removing principle are explained. Then the data interface between interpreter module and simulation system and call process flow are elaborated.The function of interpreter module can be realized and verified by building CNC based on STEP-NC. Design for CNC system based on STEP-NC is embodoid by redesigning previous CNC system based G-code. Firstly, software and hardware platform of the previous CNC system is briefly introduced, and the difference of function between CNC systems based on G-code and STEP-NC interface. According to modular design thinking and uniform data interface of previous system, the Task Generator module is selected to be the key module for redesigning, and the DLL form for interpreter of STEP-NC is proposed. By analysis, the total plan for redesigning the prevous system is put forward, and the replanting and interface design of the DLL is elaborated.To realize machining information sharing on internet, a sharing mode based on server/client is applied, with XML language expressing information of data model in STEP-NC program. On server a XML transforming module is developed, which can produce corresponding XML document according to XML template library desgined in advance and STEP-NC file. A XML parser is developed, which can land server and download and parse XML document automatically, and produce local STEP-NC machining file.Finally, based on basic theory and realization technologies introduced previously, a three-coordinate milling machine tool interfaced with STEP-NC is completed, and server/client software used for networked sharing of machining data is developed. Simulation and machining experiments demonstrate its machining ability of CNC interfaced with STEP-NC and networked sharing for machining data of server/client software...