| During the past fifty years, digital controlled machines are mostly programmed based on ISO 6983, also known as G, M code. ISO 6983 specifies the path of the center of cutter in machine coordinate, instead of the coordinate of parts. With little knowledge of machining system, machining processes are difficult to implement intelligent control. According to ISO 6983, data from CAD/CAM must be pre-processed by the post-processor before they can be used in the CNC system. Therefore, it is difficult for the CNC system to be integrated with CAD/CAM system. In the recent research and development of CNC system, a number of problems have been found with the interface based on ISO 6983. All these problems indicate that the interface has caused the bottleneck for the further development of CNC technology and the manufacturing industry. To remedy the problems existed in the interface based on ISO 6983, a new data interface named STEP-NC was presented by EU and USA. STEP-NC is strictly harmonized with ISO 10303 (STEP) and hence the data from the CAD/CAM system is ready to be used in the CNC system directly. Through the fluent data exchange based on STEP-NC, CAD/CAM and CNC can be integrated seamlessly. The basic machining unit used in the STEP-NC program is workingstep. Workingsteps are effectively machining tasks that correspond to high-level machining features and associated process parameters. With the detailed and objected-oriented description of the machining process based on STEP-NC, the forthcoming controllers for the STEP-NC system can get a comprehensive understanding of machining object, resource, condition, and thus make intelligent control of the machining process.Aiming at turning, this dissertation presents a partial development work for the intelligent STEP-NC controller. Key technologies to the simulation module in the STEP-NC controller were studied. The research will provide a theory foundation for the STEP-NC controller in controlling the cutting process intelligently.To aid the controllers in making intelligent control, simulation module is designed to be one of the key parts in the STEP-NC controllers. According to the analysis of simulation module's function, the architecture for intelligent STEP-NC turning simulation system is presented. The whole simulation system can be divided into three parts: simulation preparing part, simulation modeling part and simulation running part. In the Simulation part, tasks such as data processing, workplan making and tool path generation are executed. Simulation modeling in the simulation system can be divided into geometrical modeling and physical modeling. Physical modeling are named for the modeling of the physical factors such as cutting force, vibration, surface finish, cutting temperature and tools worn in the cutting process. Geometrical modeling is the construction of geometrical model, movement model and simulation control model. The models are simulated and then simulation results are obtained in the simulation running part. The architecture presented in this thesis provides a foundation for the STEP-NC turning simulation research.Program interpretation, process plan and tool path generation are the vital tasks for the STEP-NC simulation. In this thesis, researches are carried on for the STEP-NC program interpretation, process plan and tool path generation based on the STEP-NC standard and program. The key to the interpretation of STEP-NC program are the program translation and program information searching. A STEP-NC program file is a schema which is comprised of a set of entity instances linked by references from one to another. Entity is defined with EXPRESS language. Programming language used in geometric simulation is C++. To execute the translation task, several rules are made out for the STEP-NC description language and simulation modeling language. Using these rules, entities defined in the EXPRESS format can be translated into C++ classes. A new method for the information search based on the key words and attributes is brought forward. After the searched information is evaluated to the member of C++ class, the interpretation of the program will be completed. According to the technology description among the STEP-NC turning information, essence problems for the process plan are analyzed. A number of assistant workingsteps and operations are added to the machining process to make the workingstep running fluently. Therefore, the basic problems for the process plan are solved.A geometrical modeling method for STEP-NC turning workpiece is brought forward in this dissertation. To model the workpiece, manufacturing feature is divided into workingstep manufacturing features. Workingstep features are placed on the finished workpiece according to their position in the workpiece coordinate, through this way, the rawpiece is modeled. When the simulation is running, workingstep manufacturing features will be removed from the rawpiece conform to the sequence described in the process plan. After all the workingstep manufacturing features are removed, the simulation will be finished. Through this way, key technology for workpiece modeling is solved.Simulation and modeling of cutting force is the foundation of the STEP-NC turning process physical simulation. Using the parameters provided in the STEP-NC turning program, a mechanistic model of cutting force for the STEP-NC turning system is presented. Main impact factors of the cutting force such as workpiece materials, cutting tools material, cutting parameters and cutting parameters are described in the STEP-NC program. Relative deflections between the workpiece and the cutting tool caused by the vibration will lead to the variety of the cutting force. The variety of the cutting force results in the vibration of the cutting process and affects the surface quality. Modeling of the cutting force in the dissertation have taken the impact of the workpiece materials, cutting tools material, cutting parameters, cutting parameters and cutting process vibration into account. Using the cutting force model, impacts of the main factors to the cutting force can be assessed. Simulation environment was set using simulation software MATLAB. Simulations with the cutting force model, laws for the impact of the cutting parameters in the STEP-NC program to the cutting force are acquired. Based on the cutting force simulation function of the simulation module, the STEP-NC controller can control the cutting process intelligently.Vibration simulation is an important part of STEP-NC turning physical simulation. According to ISO 14649, expressions of the technology system parameters are brought forward. With the technology parameters and cutting parameters based on STEP-NC, the vibration simulation model is developed. In the STEP-NC vibration model, cutting parameters, tools parameters and technology system parameters are taken into account. The impacts of these factors are analyzed through the running of the vibration simulation model. With the vibration model developed in the dissertation, the STEP-NC controller can analyze and control the vibrations in the STEP-NC turning system intelligently.According to STEP-NC standard, surface roughness description for the STEP-NC turning system is put forward. Using the description, surface roughness information can be fed back to the CAD/CAM system. The description of surface roughness of STEP-NC is of great help for the integration of CAD/CAM and CNC.Surface roughness and appearance are the objects for the STEP-NC controller to control the cutting process intelligently. Two dimensional and three dimensional mathematical models for surface roughness and appearance are established. In the mathematical model, cutting parameters, tools geometry parameters and system vibrations are taken into account. Using the models to simulate the surface roughness and surface appearance, the results shows that the model can be used to analyze the impact of tool geometry parameters, cutting parameters and vibration to the surface roughness and surface appearance. Therefore, the surface roughness model and surface appearance model developed in the thesis can be used in the simulation module of the controllers to analyze the surface roughness and appearance in STEP-NC turning.A case study is used to verify the developed geometrical simulation technology and physical simulation model. A typical workpiece is used for the case study. According to the STEP-NC program of the workpiece, workpiece geometrical model and tool geometric model is constructed. With the geometrical models and the movement information in the STEP-NC program, tool path is simulated. According to the parameters presented in the STEP-NC program, physical simulation models developed in the thesis are applied to analyze the cutting force, vibration and surface finish in the machining of the workpiece. Simulation results have shown that the developed model and the presented technology are of great useful for the intelligent STEP-NC control system to analyze and control the turning process intelligently. As a result, this dissertation provides a foundation technical support for the realization of STEP-NC controller's intelligence. Simulation research will be of great helpful for the development of STEP-NC controller.
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