超精密车削刀具偏置校正方法的研究

刀具偏置的校正是超精密车削的首要任务,对提高超精密车削效率及精度具有非常重要的意义。传统的刀具偏置校正方法由于缺乏理论指导,存在校正效率低、精度低的缺点,即使利用国外进口软件进行辅助校正,也存在一些问题。对超精密车削中金刚石刀具偏置造成的车削误差展开理论分析,在理论分析的基础上,给出提高刀具偏置校正精度及效率的原则,提出一种新的刀具偏置校正方法——泰曼格林干涉仪在线检测法,并用实验证明其准确性。     

非球面超精密磨削误差建模与补偿研究

为提高课题组自研的超精密磨床加工精度,基于多体系统理论,运用齐次坐标变换原理,分析该超精密磨床37项几何误差来源,对非球面超精密磨削的综合误差建模。超精密磨床的多项几何误差元素已在制造阶段标定、补偿,取砂轮对刀误差和砂轮轮廓半径磨损误差作为主要面形误差来源,分别推导其对综合误差的传递函数,分析误差辨识方法,建立误差修正补偿模型,提出基于直接补偿的点补修正法。试验结果表明：建立的综合误差模型正确,根据误差辨识方法和修正补偿模型,修正误差后面形误差显著降低,有效提高面形精度。     

超精密车削工艺参数与表面质量关联性研究

为提高铝反射镜超精密加工的表面质量,介绍超精密切削的表面质量评价方法和影响表面质量的因素,分析各因素对表面质量的影响机制。采用单一变量法对Al6061进行不同工艺参数的单点金刚石车削实验,通过对比表面粗糙度和功率谱密度,研究各个工艺参数对表面质量的影响,并得出最佳工艺参数;最终加工出表面粗糙度为4.67 nm的光学表面。     

单晶硅超精密切削的刀具磨损试验研究

针对单晶硅超精密切削过程中金刚石刀具磨损问题,对单晶硅进行超精密车削试验。通过观察金刚石刀具磨损演变过程,分析刀具的磨损过程对表面加工质量的影响,得到刀具磨损机理。结果表明,在超精密切削单晶硅过程中,随着切削距离的增加,刀具磨损面积逐渐增加,加工过程中产生的碳化硅及类似金刚石碳颗粒与刀具后刀面发生划擦造成磨粒磨损;同时,由于交变载荷作用导致的应力疲劳现象,进而伴有解理断裂产生。当切削路程小于4km时,加工表面的粗糙度Ra值在200nm以内,切削路程大于8km时,表面粗糙度Ra值在350nm~400nm之间。     

回转体零件表面形状误差分析的小波变换方法

针对回转体零件实际加工形成的表面由多种频率成分构成的特点,为精确分解零件表面几何形状误差信号,在比较分析了传统数字滤波算法和小波算法的基础上,提出零件表面轮廓信号滤波的小波变换法。小波变换具有带通滤波的功能,它比传统的滤波方法更方便更有效。实验表明对实测信号进行小波变换滤波可以减少噪声信号的干扰,同时结合傅立叶变换可实现了表面形状误差、表面波度及表面粗糙度的综合提取,为三类误差的评定提供前题,满足了高精度测量的要求。     

超精密车削表面仿真与评价集成系统的研究

表面形貌仿真是实现高效高精度的超精密加工技术必不可少的研究方法。为了减少在理论模型的计算和表面形貌的仿真分析时间,并且实现仿真结果与测量结果的直接对比,提出一种将理论模型的仿真结果与测量仪器的分析软件进行集成的方法,并开发集成系统。文章通过研究超精密车削加工表面形貌的影响因素,基于Matlab和Bruker Wyko Vision软件,建立超精密车削加工表面仿真与评价的集成系统,为超精密车削加工工艺提供指导。通过车削加工实验中仿真和测量数据的对比结果表明,所开发的集成系统可有效应用于超精密加工领域中加工形貌仿真、加工质量评价、分析等。     

基于平面光栅的加工中心定位误差检测分析

文章介绍了德国Heidenhain公司开发的用于测量数控机床二维运动轮廓精度的高精密平面光栅,并利用平面光栅对立式加工中心定位误差进行精密测量,利用MATLAB软件对测量数据进行处理,分析X、Y坐标和定位误差之间的关系,具有一定的实用价值。     

凸轮轮廓度误差的合理评定

在检测我厂生产的ＮＪ－Ｋ００１专用数控铣床试切凸轮样件过程中,因基准孔位置误差的影响而使凸轮轮廓度误差超出公差范围,本文通过分析凸轮轮廓度误差曲线变化规律,提出一种计算机程序实现凸轮廓度误差合理评定方法。     

加工过程中各类误差项对圆柱零件的影响研究

车削加工中,分析了影响被加工零件的误差源,然后利用齐次坐标变换原理建立各种原始制造误差的数学模型,利用差分法计算被加工零件受力变形引起的加工误差,得出车削过程中各项误差对被加工圆柱零件的影响,并以实例说明加以验证。     

单点金刚石车削的工艺参数对表面粗糙度影响的实验研究

超精密车削中单点金刚石刀具切削参数的设置非常重要,这不仅关系到金刚石刀具的使用寿命,而且对于提高车削效率以及得到更好的工件表面车削质量都有着深远的意义.文章着眼于实验,首先对超精密车削中切削量、刀尖圆弧半径、进给量和主轴转速对表面微观形貌的影响进行了实验研究.然后对实验的数据结果进行了系统的归纳整理,最后分析了这些影响所产生的原因.根据实验的研究及分析的结果,可得到超精密加工切削参数的优化组合,为提高实际车削后工件的表面粗糙度提供了依据.     

A study on optimum grinding factors for aspheric convex surface micro-lens using design of experiments

As the consumer market in the optics, electronics and aerospace industries grows, the demand for ultra-precision aspheric surface micro-lens increases. To enhance the precision and productivity of ultra-precision aspheric surface micro-lens, we present an ultra-precision grinding system and process for the aspheric surface micro-lens. In this paper, an ultra-precision grinding system for manufacturing the aspheric surface micro-lens was developed by considering the factors affecting the grinding surface roughness and profile accuracy. This paper deals with the mirror grinding of an aspheric surface micro-lens by resin-bonded diamond wheel and with the spherical lens of BK7. The optimization of grinding conditions with respect to ground surface roughness and profile accuracy is investigated by design of experiments.     

Theoretical and experimental analysis of nano-surface generation in ultra-precision raster milling

The fabrication of high-quality freeform surfaces is based on ultra-precision raster milling, which allows direct machining of the freeform surfaces with sub-micrometric form accuracy and nanometric surface finish. Ultra-precision raster milling is an emerging manufacturing technology for the fabrication of high-precision and high-quality components with a surface roughness of less than 10 nm and a form error of less than 0.2 μm without the need for any additional post-processing. Moreover, the quality of a raster milled surface is based on a proper selection of cutting conditions and cutting strategies.Due to different cutting mechanics, the process factors affecting the surface quality are more complicated, as compared with ultra-precision diamond turning and conventional milling, such as swing distance and step distance. This paper presents a theoretical and experimental analysis of nano-surface generation in ultra-precision raster milling. Theoretical models for the prediction of surface roughness are built. An optimization system is established based on the theoretical models for the optimization of cutting conditions and cutting strategy in ultra-precision raster milling. A series of experiments have conducted and the results show that the theoretical models predict well the trend of the variation of surface roughness under different cutting conditions and cutting strategies.     

Investigation on the influence of tool-tip vibration on surface roughness and its representative measurement in ultra-precision diamond turning

High frequency tool-tip vibration, in the cutting force direction, is an intrinsic feature of ultra-precision single point diamond turning (SPDT). This paper is dedicated to a study of the influence of the tool-tip vibration on surface roughness. The resulting periodic fluctuation of the surface profile is identified in a particular spatial frequency range by a tangential measurement method. The ISO standard provides merely a minimal, not an optimal requirement for surface measurement. Thus, in this paper, a more representative measurement method is proposed to better characterise the machined surface in SPDT. The conventional radial and aerial surface measurements yield a relatively biased result on surface roughness which cannot adequately reflect the detrimental effect of tool-tip vibration. Representative measurement takes account of the sample area ratios and is able to be used to objectively study the discrepancies in surface measurement. The proposed model for surface generation and representative measurement are applicable to the problems in surface generation in ultra-precision SPDT, such as the spiral turning marks and spatial errors in the radial profile measurement.     

A theoretical and experimental investigation of surface roughness formation in ultra-precision diamond turning

In this paper, a model-based simulation system is presented for the analysis of surface roughness generation in ultra-precision diamond turning. The system is based on a surface roughness model which takes into account the effect of tool geometry, process parameters and relative tool-work vibration. It is evaluated through a series of cutting experiments. The results indicate that the system can predict well the surface roughness profile and the roughness parameters of a diamond turned surface under various cutting conditions. With the use of the spectrum analysis techniques, the system can also help to analyze the effect of vibration on the surface quality of workpiece and to diagnose the machine faults. The potential application of the system in process optimization is also discussed in the text.     

半球谐振子曲面加工干涉分析及其超精密磨削工艺

半球谐振子作为半球谐振陀螺的核心部件,其加工精度和表面质量直接影响半球谐振陀螺的工作精度和使用寿命。为解决半球谐振子加工难题,提高半球谐振陀螺的性能,从半球谐振子的结构特征出发,对谐振子加工过程中的干涉进行理论分析;再根据球头砂轮磨削区域分布的特点进行磨削轨迹规划,确定谐振子不同磨削阶段球头砂轮的最佳转角;最后在自研的半球谐振子超精密磨削机床上进行加工实验。超精密磨削后的谐振子表面粗糙度（Ra值）由0.6158 μm提升至0.0402 μm,面形精度（PV值）由4.5904 μm提升至0.3390 μm;经磁流变抛光后谐振子表面粗糙度（Ra值）进一步提高至0.0032 μm。研究表明:采用轨迹规划后的磨削工艺可避免砂轮与工件间的干涉,并加工出高质量的半球谐振子零件。      

A fine tool servo system for global position error compensation for a miniature ultra-precision lathe

There is an increasing demand for single-point diamond turning to manufacture micro components as well as micro features on a large workpiece surface. In order to obtain high accuracy and a fine surface finish of the large area workpiece, position control of machine tool has become the main concern to achieve the high precision position control. A coarse-fine servo system is able to provide a cost-effective solution. This system can provide information on the entire guidance errors profile data and simultaneously compensate the error in real-time by using the fine position control technique. In this study, a piezoelectric actuator based fine tool servo (FTS) system has been developed and it has been incorporated with a miniature ultra-precision lathe. A cost-effective position sensitivity detector (PSD) is integrated in the FTS design, which is able to measure the global straightness error of the translational slide accurately. The detected error signals are compensated by the FTS during the turning process. For better tracking performance, a proportional-integral (PI) feedback controller has been implemented and tested in this study. Experimental results show that the developed FTS can effectively and successfully compensate the micro waviness error which is caused by the x-axis translational slide of the miniature ultra-precision lathe.     

Dynamic multiphase modeling and optimization of fluid jet polishing process

Fluid jet polishing is a machining process used increasingly in the ultra-precision manufacture of optical components and replication molds. While the process bears some similarities with abrasive water jet machining, it operates at much lower pressure and grit size. This paper presents a computational fluid dynamics model based on latest multiphase turbulent flow computational methods, simulating dynamically the interface between fluid and air. The model is then used to optimize surface texture performance down to 1 nm Ra on electroless nickel plated optical dies, while removing diamond turning marks. Some conclusions are drawn regarding the nature of the removal mechanism.     

Ultra-precision polishing of electroless nickel molding dies for shorter wavelength applications

Electroless nickel is one of the best materials for making optical molding dies, because of its machinability with both single-point diamond turning and polishing, as well as its suitable hardness and durability. This paper deals with the ultra-precision polishing of aspheric molding dies for next-generation hard X-ray telescope mirrors, which require a super smooth surface with a roughness below 0.3 nm root-mean-square (rms). The material was machined using various methods, and a surface roughness of 0.23 nm rms was obtained on aspheric molding dies of 300 mm in diameter. A surface roughness of 0.16 nm rms was achieved on platinum/carbon multilayer mirrors, replicated from plano dies.     

Characterisation of nanosurface generation in single-point diamond turning

This paper describes a parametric analysis of nanosurface generation in single-point diamond turning (SPDT). The properties of the surface roughness profiles were extracted and analysed using the power spectrum analysis method. A series of face cutting experiments was undertaken on an aluminium alloy under various cutting conditions. The results indicate that the power spectrum of a surface roughness profile is basically composed of several periodical components that can be correlated to different process parameters and mechanisms of surface generation. Moreover, it is found that the tool feed, tool geometry, spindle error motions and relative vibration between the tool and the workpiece are not the only dominant components contributing to the surface generation in SPDT. Materials swelling and tool interference are other important factors. Based on these findings, relationships are proposed to explain the influence of tool interference on the variation of the spectral components and process parameters. The implications of these findings on the optimisation of the surface quality in SPDT are also discussed.