Study On The NC Turning Simulation Based On Imitated-solid

For a long time, as the most economic method to manufacturing products with high quality and surface integrity, machining plays an important role in the national economy. Due to the variety of work-piece material and the versatility of the process parameters, the study on the machining process is limited to empirical extent for a long time. It not only leads to low machining efficiency, but also results in high manufacturing cost and frequent errors even accidents in machining process. Machining simulation is one of the important applications of computer simulation in modern mechanical manufacturing industry. It is of great significance in producing quality parts more quickly and economically.Based on the characteristics of machining simulation, the imitated-solid conception system and modeling system for machining simulation is presented in this paper, and its key realizating technologies for NC turning simulation based on imitated-solid is studied in detail.1. Though extensive investigation, the existed methods of machining simulation can be divided into three acspects: geometric simulation, physical simulation, and process simulation. The principle of the dominating algorithms in these three acspects is introduced. The advantages and disadvantages for those algorithms are summarized, and the developing trends for machining simulation are also discussed.2. Based on the essence of metal cutting, the imitated-solid conception system for machining simulation is presented. Here, Imitated-Solid is the "actual object" formed by computer which can represent the intrinsical characteristics of the object in real machining environment. According to its influence to the machining result, the imitated-solid in the virtual machining environment can be devided into two kinds: divisible imitated-solid and indivisible imitated-solid. The divisible imitated-solid is supposed to be constructed by the particles which can represent its basic characteristics, and here named it as "Micro-solid". The constructing guideline and mode of micro-solids in divisible imitated-solid is presented. In term of the guideline, the divisible imitated-solid can be portioned into two zones: kernel and boundary, and the micro-solids in these zones are classified into geometric micro-solids and dynamic micro-solids respectively. Based on the character of object in real machining environment, the indivisible imitated-solid can be classified into two formats: indivisible part imitated-solid and indivisible assembly imitated-solid. The principle and process of machining simulation based on imitated-solid theory is presented. Take NC turning as an example, the structure of imitated-solid machining simulation system is presented.3. According to the imitated-solid conception system for machining simulation, the key technologies for its realization in NC turning is discussed thoroughly, the modeling system for machining simulation is established.Based on the feature modeling technology, the geometric and apparent features of undivisible part imitated-solid are described in detail, the model of undivisible part imitated-solid isdeveloped. Based on the features of components in the real machine tools, the undivisible assembly imitated-solids can be formed by assembling undivisible part imitated-solids with certain positional relationship.According to the influence of cutting tool to the micrometric structure of workpiece in the machining process, the constructing structure of dynamic micro-solids in the workpiece imitated-solid kernel zone are determined. The dynamic micro-solid is supposed to be indiscerptible rigid body with certain mass which can reflect the essential characters of the workpiece material. Based on Morse potential energy function, the interacting relationship of dynamic micro-solids is developed. In terms of the second classical Newtonian equation of motion, the kinetic model of dynamic micro-solids is presented. Based on the aforementioned models, the turning simulation of workpiece imitated-solid kernel zone is realized.Introducing the fractal theory into the modeling of workpiece imitated-solid boundary zone, the fractal constructing structure model of boundary zone that unit length is increased in 2's exponents is developed. In terms of the revolving feature of the turning workpiece and its in-between shapes, the quasi-sector shape is determined to be the basic fractal shape for turning. Based on the constructing structure model and basic fractal shape, the model of workpiece imitated-solid boundary zone for turning is obtained, and the process simulation of boundary zone is realized.According to the twist shape of the natural curled chip, the basic shape for geometric micro-solid in chip imitated-solid is supposed to be quasi-sector shape. Though investigating the all kinds of factors affecting chips' forming and curling, the geometric parameters controlling the chip shape are caculated, and the natural curled chip model for different cutting parameter group which is resemble to the real circumstance is obtained. Based on the positional relationship of workpiece and cutting tool in the time of chip forming, the chip breaking model is presented, the function for chip classes judging is developed, the dynamic simulation for chip's forming, curling and breaking is realized.Aimed to the limitation of present NC code compiler, e.g. specialization and difficult tomaintain, a method of developing NC code compile module by using special compiling tools------Lex&Yacc is presented. By presenting the method of system customization, the compile module can adapt various codes from different NC system.Intergrated the aforementioned models together, the imitated-solid simulation system for NC turning is established. The 3D turning simulation which can describe the microscopical geometric and physical change of the material and its macroscopical interaction results is realized.