【作者】 吴菁；

【导师】 姚英学；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 制造业是现代国民经济的重要支柱产业,数控加工技术在制造业中占有重要地位。在实际数控生产加工中,切削速度、进给量、背吃刀量等加工参数通常由编程人员指定,为避免过大的切削力、切削振动等导致机床损坏和零件加工精度降低现象的发生,编程人员往往牺牲加工效率而选择非常保守的切削参数,从而严重影响和限制了数控设备的使用效率和应用范围。针对以上加工中存在的问题,本课题以提高数控机床加工效率、降低加工成本和获得高质量产品为目的而进行了数控车削加工参数优化方法的研究,研究成果具有广泛的经济效益和社会效益。虚拟加工技术是当前加工仿真技术发展的一个新阶段,不仅能提供逼真的加工环境仿真,而且在仿真过程中考虑了机床系统的运动控制和动态特性。本文开展了基于虚拟加工车削参数优化方法的研究,对基于虚拟加工车削参数优化方法的原理进行了分析,建立了基于虚拟加工车削参数优化方法的体系结构,包括功能体系结构和组织体系结构,并确定了具体的优化工作流程。基于虚拟加工车削参数优化方法的前提是实现准确的加工过程仿真,本文开展了利用实体仿真技术进行加工过程仿真的研究,研究了数控车削加工的几何建模方法,实现了利用刀具扫描体与工件模型进行布尔减的加工仿真过程。通过将三维实体模型转换为二维多边形模型,有效地减少了计算时间,提高了仿真速度。在加工过程仿真同时利用“裁剪多边形”获取瞬时背吃刀量和切削工件半径为切削加工性能预测和切削参数优化奠定基础。在仿真过程中,通过经验公式模型预测车削加工动态切削力,实验结果表明预测值与测量值较好吻合,证明仿真系统具有较好的加工性能预测能力,同时也间接验证了切削参数获取方法的正确性。在总结了单程切削加工特点的基础上,确定了以离散加工路径分段进行切削参数优化的策略。优化变量选定主轴转速和进给量。建立了恒主切削力与效率相结合的多目标优化函数,制订了单程切削加工中的约束规则。对应用遗传算法求解切削参数优化数学模型的可行性进行了分析。采用遗传算法对切削参数优化数学模型进行寻优求解。通过仿真计算,分析了遗传算法中最大迭代次数、交叉概率和变异概率对优化结果的影响。通过重复性仿真计算的方法验证了优化方法的可靠性。在分析多程切削加工特点的基础上,研究了多程切削加工的参数优化方法。以单件产品最低加工成本为目标,建立优化参数的数学模型,制订相关约束条件。数学模型建模中考虑了瞬时工件加工半径对优化结果的影响,克服了以往优化数学模型过度简化的局限性。通过单程切削加工优化模型建立优化参数数据库,利用整数非线性优化算法优化切削参数,以达到节省加工成本的目的。通过实例计算,结果表明:所用算法较好地解决了多程切削加工中循环次数的确定和总加工余量分配的问题。以VC++6.0为工具,开发了具有实体仿真功能的基于虚拟加工的切削参数优化软件系统。系统以车削加工几何建模技术为基础,可实现单程切削加工和多程切削加工参数优化,并自动生成能够实际生产的数控程序代码,使数控编程更加智能化。利用该系统根据恒主切削力和效率的组合优化目标对粗加工数控车削程序进行了优化,并应用优化前后的数控程序进行了实际切削加工实验。实验结果验证了基于虚拟加工车削参数优化方法的有效性和可靠性。更多还原

【Abstract】 Manufacturing industry is an important pillar of the modern industrial economy, CNC machining technology in the manufacturing industry occupies an important position. In the actual processing of CNC, the processing parameters of the cutting speed, feed rate, cutting depth, etc. are often specified conservatively by the programmer in order to avoid excessive cutting force, vibration machine, which lead to damage machine and reduce machining precision, thus seriously limiting the efficiency in the use of numerical control equipment. The paper studies the method of CNC turning parameters optimization for the purpose of enhancing efficiency, reducing processing costs and accessing to high-quality products, the results have a wide range of economic and social benefits.Virtual machining simulation technology is a new stage of development of the current processing technology, it not only provide a realistic simulation of the processing environment, but also take into account the process of motion and dynamic characteristics in the geometric and physical simulation. This paper studies on the method of cutting parameters optimization based on virtual machining, the architecture is analyzed, which includes the function architecture and organizations architecture, and the workflow is identified.Because machining simulation is the basement to the cutting parameters optimization, the method of geometric modeling is proposed and the machining simulation process is realized by the use of the Boolean with the model of tool swept volume and work piece. It can effectively reduce the calculation time and improve the simulation speed by three-dimensional solid model converted to two-dimensional polygon model. At the same time in the machining process simulation, cutting parameters such as cutting depth and radius are acquired by the method of "polygon clipping", which are the basis of processing performance prediction and cutting parameters optimization system. In the simulation process, cutting force model is established with the empirical formula, the experimental results show that the predicted values are similar with the measured, which proves the simulation system has better predictive capability of processing performance and also indirectly verifies the correctness of acquired method of cutting parameters.Based on the conclusion of a single pass turning machining features, cutting parameter optimization strategy is determined on the basis of a discrete sub-processing path. Variables selected to optimize are spindle speed and feed rate. The function of constant cutting force is established a with efficiency, the rules of constraint of single pass turning are determined. The feasibility of genetic algorithm for optimization of single pass cutting parameters is carried out. The genetic algorithm is used. Through simulation, the optimization results are compared with the different largest number of iterations, crossover probability and mutation probability. The reliability of the optimization method is verified through repetitive simulation methods.Based on the conclusion of multi-pass turning machining features, the cutting parameters optimization method is researched. A mathematical model of minimum costs is the established. The instantaneous radius of the workpiece processing is considered in the mathematical modeling, which overcomes the limitations of over-simplification in the previous model. The integer nonlinear optimization method and GA algorithm are used to optimize cutting parameters in order to achieve the purpose of saving processing costs. Through examples, the results show that the algorithm can solve the problem of identification of multi-pass turning cycle times and allocation of the total allowance.With VC++6.0, a cutting parameter optimization system based on NC turning simulation is developed. Using the optimization system, spindle revolutions and feed rates in NC file for rough machining are optimized according to the multiple objectives: the constant machining forces and increasing machining efficiency. Using the optimal NC file, turning experiments are carried out and the experiment results show the validity and reliability of cutting parameters optimization system.更多还原