Research On STEP-NC Based On Internet

Since the current CNC language(G code)delivers only limited information to CNC,it makes nothing but an executing mechanism completely unaware of the motion being executed.Furthermore CNC is isolated with CAD,CAPP and CAM without understanding high level information.Now,a new and comprehensive language for CNC,called STEP-NC is established.Since the new language accommodates various high level information,the STEP-NC can undertake various intelligent functions.And this high level information can makes CAD/CAM and STEP-NC integrated.Combined with network technology,computer integrated manufacturing system based on internet can be implemented. Because of the open architecture,STEP-NC can solve the problem of curve interpolation and surface interpolation easily.Surrounding these areas,four parts are studied in this thesis.1.Based on studied STEP and STEP-NC,emphasize that the machining feature is used in STEP-NC,but design feature in STEP.The machining feature model for STEP-NC is proposed.About the machining feature,the definition,classified method and structure of information are discussed.The idea of machining feature modeling is cutting the machining features from the stock same as manufacturing the part.The developed methodology was implemented in a prototype based on pro/ENGINEER software and SQL Server 2000,and tested with a practical example.2.A knowledge base is established,which core is machining features. The tables arranged according to the structure of STEP-NC,which can make information sharing and implement CAPP easily.An optimum operation sequencing algorithm is developed with reduced dependence on human judgment.For the practical example process planning is completed and STEP-NC file is achieved.3.Based on studying of STEP-NC information model and XML, two-level implementation method based on schema is proposed to convert STEP-NC into XML.Using XML,STEP-NC data can be shared for networked manufacturing and cooperative manufacturing in different places.At last STEP-NC data is shown by a tree and some tables,so it is easy to use by operator.Furthermore,an interface from STEP-NC files to traditional CNC files is developed.Therefore using STEP-NC a component can be processed directly in a CNC machine tool.The business model and architecture of manufacturing process based on SOA and web service are studied.The structure of SOA and web service technology is discussed.4.An efficient real-time NURBS curve interpolator for high-speed and high-accuracy curve machining is developed and implemented,which considers the confined contour error,the acceleration/deceleration planning and the machine dynamic response simultaneously.A practical method is proposed to adjust the feed rate to the curvature radius of NURBS curves to achieve higher machining precision.However,at the sharp corner of the curves,the feed rate fluctuation might result in large impacts to machine tools.The offline pre-interpolation for sharp corners is presented.The feed rate is reduced in advance according to the machine's acceleration capability as well as satisfying the confined contour error.The velocity profile can be chosen dynamically to meet the requirements of the machining process by means of the flexible acceleration/deceleration planning.In addition,a new strategy based on the geometrical properties of NURBS curves is suggested to predict the deceleration point.Therefore,the process of acceleration and deceleration is so smooth that it can satisfy the need of the machining process.With open architecture STEP-NC can solve the problem of cutting curves and surfaces directly using this algorithm.