【作者】 张海军；

【导师】 周明；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 微结构表面因其具有某些特定的性能,如光学特性、粘附性、摩擦性、润滑性、耐磨损性等,在民用和军用工业领域都有很广阔的应用背景。基于FTS超精密切削加工技术因其具有高频率响应、高定位精度等特点,已经成为微结构表面切削加工的一种主流技术。目前,世界上发达国家已经应用该技术成功地加工出了高精度的微结构表面,并已实现了工业应用。国内对该技术的研究还处于起步阶段,其中的关键基础技术还没有完全掌握,加工质量与国外相比还有一定差距。基于此,本文针对基于FTS切削加工微结构表面的关键性基础技术进行了研究。良好的刀具轨迹是获得高品质微结构表面的前提。使用FTS加工微结构表面时,微结构表面形貌是由主轴转角、X向溜板及FTS共同插补而成,这与常规的车削过程中工件表面形貌形成方式有所不同,因此需要使用特殊的刀具运动轨迹生成策略,同时由于FTS的行程有限,并不能直接加工大幅值的非回转对称微结构表面。为解决这些问题,本文提出了等弧长刀具轨迹驱动点生成策略,并基于曲面分解与重构原则,研究了大幅值微结构表面刀具轨迹的生成方法。为了提高刀具轨迹的精度,本文基于矢量数学原理,研究了由刀具几何参数和安装引起的刀具参考点位置误差的补偿方法。通过加工实验对上述理论的正确性和有效性进行了验证。实验结果表明,采用补偿后的刀具轨迹,使已加工表面粗糙度和面形误差都有了明显地降低。刀具技术是获得高质量微结构表面的关键技术。在微结构表面加工过程中刀具几何参数和刀具使用寿命是两个非常关键的问题。不合理的刀具几何参数会使刀具与已加工表面发生切削干涉,降低微结构表面的廓形精度和加工质量。为了避免切削干涉,在微结构加工过程中不得不使用尖刀形式的刀具,而这种刀具的使用寿命较短,限制了其在实际中的应用。因此,有必要对微结构表面加工用金刚石刀具的几何参数设计和刀具磨损进行研究,以便提高微结构表面加工质量和延长刀具使用寿命。本文提出了基于微结构表面特征的刀具主要几何参数设计原则。通过正弦波微结构表面的加工实验,研究了微结构表面加工用特种金刚石刀具磨损形式和磨损机理。实验结果表明,金刚石石墨化是刀具磨损的主要机制;微结构表面加工过程中的微冲击效应是导致刀尖破损的主要原因。在微结构表面加工过程中,切削深度随着微结构表面轮廓不断变化,刀具运动存在位置和速度的突变,这种突变会引起切削力的波动,易激励系统引起振动,导致切削过程不稳定,造成加工表面质量下降。所以,FTS的控制系统不仅要消除压电陶瓷本身的非线性效应,还要解决加工过程中切削力波动等因素引起的外界干扰。为了实现这一目的,文中提出了一种基于组合趋近律的FTS滑模变结构控制策略,并通过加工带有凸台结构的微结构表面对这一控制算法与基于指数趋近律的滑模变结构控制算法进行了对比实验,实验结果验证了该控制策略的有效性和正确性。由于不同的微结构表面具有特定的轮廓形状和特征尺寸,需要采用不同的加工参数和加工条件进行加工。为了减少优化工艺参数的实验次数,获得较高品质的微结构表面,本文以Matlab/ Simulink作为工具,综合考虑加工过程中线性和非线性因素的影响,建立了集刀具轨迹生成及补偿、刀具设计原则、机床控制系统、机床动力学系统特性、表面生成及表面评价于一体的基于FTS切削微结构表面加工过程仿真系统。通过正弦波微结构加工实验验证了该系统的正确性。利用该系统研究了主轴转速和进给量对方坑非回转对称微结构表面质量的影响,获得了优化的加工参数,并加工出了方坑非回转对称微结构表面。更多还原

【Abstract】 The microstructured surfaces are widely used and have good prospects in lots of military and civilian industries applications, as their special and unique engineering functions, such as optical, conglutinative, tribological, lubricative, anti-abrasive characteristics and so on. Diamond cutting based on FTS featured high dynamic response and high positioning resolution is a popular microstructured surfaces manufacture technology. Some precision microstructured surfaces fabricated with FTS have been used industrially in many advanced countries. However the research on FTS diamond cutting of microstructured surfaces technology is at start stage in our country. In this dessertion, some works have been done to reduce the gap between our country and foreign countries in the research on ultra-precision machining of microstructured surfaces.High-precision tool path is a precondition for obtaining high quality microstructured surfaces which were formed by the position of spindle, X slide and FTS system. A special tool path generating method should be adopted in order to obtain high precision tool path for machining microstructured surfaces as the special cutting process. In addition to, the microstructured surfaces with large amplitude cannot be finished with FTS because of its shorter stroke. In this dissertation, the method of large amplitude microstructured surfaces tool path generation and allotment was studied base on freeform decomposing and reconstructing principle. A strategy of tool path drive points has been proposed. The compensation arithmetic of tool reference point position error caused by tool geometries and setting error was deduced base on vector mathematics. The methods and arithmetic mentioned above have been proved by trail results. The experimental results showed that the machined surfaces quality and form accuracy of microstructured surfaces manufactured with cpmpensated tool path have an obvious improvement.Tool geometries and tool wear are two key factors of affecting microstructured surfaces quality. A phenomenon of over cutting will appear with unreasonable tool geometries. The application of diamond cutting in practice for manufacturing microstructured surfaces is often limited by the rapid wear of diamond tools. In the dissertation, a general tool geometries design principle to avoid over cutting was proposed according to the 3D profile of microstructured surfaces. The wear of sharp point tip diamond tool was investigated by a series of sinusoidal microstructured surfaces cutting tests. The experimental results showed that the patterns of micro diamond tool include smooth wear with a low feed rate and catastrophic fracture with a high feed rate. The wear mechanism is believed that the diamond on the tool edge and tool tip has been transformed into graphite under the effect of the alternating cutting force loads, cutting thermal loads and micro impact loads in the cutting of microstructured surfaces. The wear of diamond tool with different geometries also was studied experimentally. The experiment results afford a foundation to design and employ diamond tool in diamond cutting of microstructured surfaces.The depth of cut changes along the profiles of microstructured surfaces in the diamond cutting process. The position and velocity of diamond tool movement is not smooth as the existence of sharp corner and step profiles which can cause fluctuation of cutting forces, excite cutting system vibration and make cutting process unstable. Therefore the task of FTS control system is not only to eliminate non-linearity characteristics of piezoelectric actuator but also to decrease effects of disturbances caused cutting force and un-modeling factors. In this case, a variable-structure sliding-mode control with combination approach arithmetic was proposed. The comparison with exponential approach arithmetic was fulfilled experimentally.In order to reduce cutting parameters optimization tests and obtain high quality machined surfaces, a simulation model was established with Matlab/Simulink for diamond cutting process of microstructured surfaces with FTS. Tool path generation and compensation, diamond tool geometries design, control system characteristics, machine tools dynamic response and surfaces generation were integrated in the model. Some linear and non-linear factors also were considered. The simulation model was validated with sinusoidal microstructured surfaces cutting tests. The effects of spindle speed and feed rate on the machined surfaces quality of micro square-pit non-rational symmetric surfaces were investigated by the simulation model. The square-pit non-rational symmetric surfaces were manufactured with the optimization cutting parameters which obtained with the simulation model.更多还原