新型直线/回转式快速刀具伺服装置的设计

基于快速刀具伺服(Fast Tool Servo,简称FTS)的金刚石车削加工技术被认为是一种非常有发展前景的光学自由曲面加工方法,针对目前单自由度FTS加工技术中存在的刀具伺服运动与机床同步问题,以及刀具在x向匀速进给带来的影响,设计了一种新型的直线/回转式FTS装置,采用压电陶瓷驱动柔性铰链实现,能够输出z向的线性位移和绕y轴摆动,用于调节刀具在x向和z向的位置,使刀具的伺服运动与机床运动完全同步,并实现自由曲面的变进给车削加工,可提高加工精度以及改善被加工表面质量。根据应用的实际情况,详细分析了FTS设计要求,并对设计的柔性铰链结构进行了有限元分析,结果表明该结构在内应力和共振频率方面满足应用的要求,可用于光学自由曲面的车削加工。     

大行程快速刀具伺服装置的设计

基于快速刀具伺服(Fast Tool Servo,FTS)的金刚石车削加工技术是一种非常有发展前景的光学自由曲面加工手段。以柔性铰链和音圈电机为主要元素,研制一套大行程快速刀具伺服系统,该系统具有刚度大、工作稳定性好、阻尼可调等优点。详细介绍了柔性铰链的设计与分析、FTS系统性能测试和自由曲面切削试验,新型FTS系统的跟踪误差为0.12%,运动分辨率优于0.04μm,可以获得Ra30nm的光学自由曲面。测试和加工结果表明,新型的FTS系统可以用光学自由曲面高效、高精密金刚石车削加工。     

新型直线回转式快刀伺服装置的性能测试与分析

基于快刀伺服的金刚石车削技术是光学自由曲面、非圆柱面和微结构表面等方面高效率、高精度的加工技术,受到国内外的广泛关注。在该技术中,随着被加工曲面面型的变化,刀具的瞬态工作前角会实时发生变化,而影响刀具磨损、切削力的变化以及切削稳定性。设计一套直线回转式快刀伺服装置,可在自由曲面车削中实现刀具工作前角的调整。该装置实现了亚微米级的工作精度和10nm的运动分辨率。试验测试的结果表明该装置具有了良好的工作性能。     

基于AKIMA插值的光学自由曲面刀具路径优化

FTS金刚石车削技术是加工复杂光学自由曲面加工的主要方法之一。为解决自由曲面难加工,效率低,插值误差波动大的问题,设计曲面离散出刀触点,采用AKIMA插值法对金刚石刀具圆弧半径进行刀具轨迹补偿,生成机床可识别的刀位点轨迹。通过MATLAB仿真实验表明,AKIMA插值法总体上更能逼近理想轨迹,虽然提出的插值方法计算相对复杂,但是插值精度显著提高,能够很好地控制曲面轮廓,保证了曲面的面型精度,同时也满足加工效率方面的要求。     

超精密慢刀伺服车削零件的面型分析与刀具设计方法研究

研究首先分析总结了当前自由曲面复杂零件超精密慢刀伺服车削加工中的具体加工技术挑战,进而系统地研究了自由曲面零件面型特性,零件面型关键参数提取,零件面型参数与刀具参数之间的关联关系。进一步研究了超精密慢刀伺服车削金刚石刀具的几何参数确定方法;并针对自由曲面零件的可加工性,提出了超精密慢刀伺服车削加工中金刚石刀具选用准则。另外,通过超精密慢刀伺服车削加工实际案例和应用加工试验,证明零件面型分析及金刚石刀具几何参数的合理选用,对实现高效稳定的工业化超精密慢刀伺服车削加工至关重要。     

复杂曲面慢刀伺服加工刀具半径补偿方法

随着机床技术的进步,一种基于慢刀伺服技术的超精密金刚石车削创成加工方式成为可能,能够一次加工获得精度很高的各种复杂曲面。在复杂曲面慢刀伺服车削加工路径规划中,针对存在的刀具过切现象,传统刀具半径补偿算法为计算曲面刀触点的等距点,通过分析传统等距点刀具半径补偿算法的不足,提出了一种基于等距点的刀具半径补偿算法,弥补了传统等距点刀具半径补偿算法的不足,通过实例证明该算法有效地改进了传统刀具半径补偿算法的不足,提高了曲面加工的精度。     

微透镜阵列单点金刚石车削补偿技术

为了提高微透镜阵列单点金刚石车削的加工精度与一致性,提出了加工误差的理论模型,并针对其补偿方法进行了理论分析和实验研究.将微透镜阵列加工等效为自由曲面加工,通过建立单点金刚石慢刀伺服切削模型,计算了理论曲面在每一个切削点处沿切削方向的曲率半径;结合刀具等效倾斜角模型和机床加工时延模型,进一步得到了慢刀伺服切削微透镜阵列...     

基于多误差源耦合的五轴数控铣床加工误差综合预测及评判

在综合考虑机床动静态多种误差源的基础上,建立了各运动轴伺服运动模型和多体联动模型,给出了刀具的实际运动位置和姿态,基于包络理论求解了曲面加工实际成形面,对比理想数学模型,对加工误差进行了综合预测和评判。以复杂非可展曲面--S试件为例,给出了S试件的铣削精度构建方法,分析了机床动态因素(位置环、速度环等)对零件铣削精度的影响,并通过切削实验后的数据回归分析予以验证。建立了基于神经网络的机床铣削误差辨识模型,用于评估机床加工后的状态。该平台的搭建为实现大型、关键零件的加工精度预测和保障提供了技术支撑。      

机床加工误差补偿信号的实时测量系统

机床加工误差补偿是提高加工精度的重要途径.正确测量机床主轴误差运动是实现加工误差补偿的前提.然而,这一测试问题一直未得到很好解决.本文提出的用差动传感器直接相对主轴表面测量的系统比较简单,容易实现,且为实时测量.该方法已用于车削加工误差实时补偿系统之中,取得了较好的效果.     

超精密慢刀伺服金刚石车削加工的关键工艺问题研究

根据超精密慢刀伺服金刚石车削加工原理,以自由曲面为例,系统地分析了超精密慢刀伺服加工中工件面型对刀具参数和关键切削工艺参数的特殊要求,进一步归纳提出了复杂曲面慢刀伺服车削中的刀具选择和设计准则。该研究工作同时借助Nanotech 250 ULv2机床和UG对切削方向与刀触点布局方式,以及关键切削工艺参数进行了慢刀伺服加工路径仿真和超精密车削试验研究。结果表明合理的切削方向与刀触点布局及加工工艺参数选择,有助于实现自由曲面工件高效稳定可控的超精密慢刀伺服加工。     

An accurate interpolator for FTS diamond turning of optical free-form surface

The ultra-precision components with freeform surfaces are used in a wide range of areas such as automotive, aerospace, optical, metrology artifacts, and data storage. Fast tool servo (FTS) diamond turning has been considered as one of the leading techniques to produce such components. We present four points mean value interpolator for FTS diamond turning. Performance is compared between the NURBS interpolations with the proposed interpolation using Matlab, which shows that the proposed interpolation not only improves the surface accuracy of the freeform surface, but also meets the real-time requirement.     

微结构自由曲面的超精密单点金刚石切削技术概述

回顾了超精密加工技术的发展,主要包括超精密加工设备的开发历程,以及超精密单点金刚石切削技术基础,并对微工程技术作一简要介绍;重点论述微结构自由曲面的微纳切削技术,包括单点金刚石车削(Single point diamond turning, SPDT),快刀伺服加工(Fast tool servo, FTS),金刚石微凿切(Diamond micro chiseling, DMC),光栅铣削等技术。指出微结构自由曲面测量领域面临的挑战和存在的问题,包括接触式测量和非接触式测量。通过几个典型微结构自由曲面的加工及测量的应用进行举例说明;最后介绍我国在超精密加工机床领域内的研制情况,展望了超精密切削技术未来发展趋势。     

F-Theta自由曲面透镜的精密与镜面磨削

针对光学玻璃的F-Theta自由曲面透镜加工困难等问题,提出将金刚石砂轮的椭圆环面代替圆环面,进行F-Theta自由曲面磨削加工,研究形状误差的补偿磨削方法和光学玻璃的镜面磨削工艺。根据F-Theta透镜的自由曲面建立砂轮与工件相切的刀具轨迹法向算法。采用#46粗金刚石砂轮修整成椭圆环面,提出自由曲面磨削的法向误差补偿加工模式。最后,采用#3000超细金刚石砂轮的椭圆环面进行轴向磨削试验。试验结果表明:传统的垂直误差补偿磨削可减小面形误差45.9%及其PV值11.6%;而新提出的法向误差补偿磨削可减小面形误差47.9%及其PV值41.5%。此外,超细砂轮磨削可使得自由曲面的粗糙度达到28 nm,其镜面磨削工艺有别于较粗砂轮磨削工艺。因此,椭圆环面砂轮的法向补偿磨削是提高自由曲面加工精度的有效方法,而且,无需研磨抛光就可以实现光学玻璃的自由曲面镜面磨削。     

A novel surface analytical model for cutting linearization error in fast tool/slow slide servo diamond turning

Fast tool/slow slide servo (FTS/SSS) technology plays an important role in machining freeform surfaces for the modern optics industry. The surface accuracy is a sticking factor that demands the need for a long-standing solution to fabricate ultraprecise freeform surfaces accurately and efficiently. However, the analysis of cutting linearization errors in the cutting direction of surface generation has received little attention. Hence, a novel surface analytical model is developed to evaluate the cutting linearization error of all cutting strategies for surface generation. It also optimizes the number of cutting points to meet accuracy requirements. To validate the theoretical cutting linearization errors, a series of machining experiments on sinusoidal wave grid and micro-lens array surfaces has been conducted. The experimental results demonstrate that these surfaces have successfully achieved the surface accuracy requirement of 1 μm with the implementation of the proposed model. These further credit the capability of the surface analytical model as an effective and accurate tool in improving profile accuracies and meeting accuracy requirements.     

Theoretical and experimental analysis of the effect of error motions on surface generation in fast tool servo machining

The fast tool servo (FTS) machining process provides an indispensable solution for machining optical microstructures with sub-micrometer form accuracy and a nanometric surface finish without the need for any subsequent post processing. The error motions in the FTS machining play an important role in the material removal process and surface generation. However, these issues have received relatively little attention. This paper presents a theoretical and experimental analysis of the effect of error motions on surface generation in FTS machining. This is accomplished by the establishment of a model-based simulation system for FTS machining, which is composed of a surface generation model, a tool path generator, and an error model. The major components of the error model include the stroke error of the FTS, the error motion of the machine slide in the feed direction, and the axial motion error of the main spindle. The form error due to the stroke error can be extracted empirically by regional analysis, the slide motion error and the axial motion error of the spindle are obtained by a kinematic model and the analysis of the profile in the circumferential direction in single point diamond turning (SPDT) of a flat surface, respectively. After incorporating the error model in the surface generation model, the model-based simulation system is capable of predicting the surface generation in FTS machining. A series of cutting tests were conducted. The predicted results were compared with the measured results, and hence the performance of the model-based simulation system was verified. The proposed research is helpful for the analysis and diagnosis of motion errors on the surface generation in the FTS machining process, and throws some light on the corresponding compensation and optimization solutions to improve the machining quality.     

Optimal selection of machining parameters for fast tool servo diamond turning

Ultraprecision machined components with micro-structured surfaces in micrometer or nanometer range have gained wide applications especially in optical industry. A technique called fast tool servo (FTS) diamond turning is superior in fabricating precision and complicated micro-structured surfaces with wavelength above tens of microns. However, in order to obtain optimal machined surface quality, the machining parameters need to be selected carefully. In this paper, optimal selection of the machining parameters, including spindle speed, sampling number, feedrate and tool geometry, for fabricating micro-structured surfaces by FTS diamond turning is presented. A simulation system is developed to select feedrate and tool geometry by computing the theoretical surface roughness, spindle speed, and sampling number based on the FTS dynamics and the motion controller capability. Experiments have been carried out to show the effect of the machining parameters. In addition, machining of typical micro-structured surfaces with machining parameters selected by the presented approach proves the effectiveness of the proposed optimal machining parameters selection method and the designed FTS diamond turning machine.     

基于FTS的非轴对称微结构表面超精密切削系统研究

介绍了基于快速伺服刀架(FTS)的微结构表面超精密金刚石车削加工系统,并利用该系统成功实现了典型非轴对称结构正弦网格表面的加工。作为FTS的驱动元部件,压电陶瓷微位移驱动器的迟滞、蠕变非线性特性大大影响了系统的动态性能与加工精度。因此,建立了基于拓展输入空间法的FTS神经网络逆模型,并结合PID反馈控制,实现了FTS的闭环控制。实验结果表明,该控制策略可以有效提高FTS的动态性能,其跟踪误差小于150 nm,为微结构表面的加工提供了可靠的保证。     

光学自由曲面的超精密加工技术及应用

光学自由曲面是指非对称性、不规则、不适合用统一的光学方程式来描述的光学曲面.自由曲面光学元件在光电产品及光通讯产品中的应用日益广泛.采用多轴超精密金刚石机床加工光学自由曲面,可达到亚微米级形状精度和纳米级表面粗糙的高精度水平.文章介绍了光学自由曲面的超精密加工技术及其在光电产品领域的应用,并开发适合几种典型光学自由曲面超精密加工的刀具轨迹自动生成软件.     

红外线聚光非球面透镜的单点金刚石镜面切削方法

根据硬脆性材料的延性域加工机理和面形误差补偿加工方法,研究了圆弧形和平头形刀具的单点金刚石延性域切削方法,在加工中直接获得了镜面切除面;并利用数控技术进行误差补偿,克服了因加工试验、刀具磨损、机械振动、热变形等造成的加工误差导致的非球面的面形精度降低和表面粗糙度恶化.并将该方法用于采用圆弧形刀具对红外线聚光的φ70mm非球面锗透镜进行单点金刚石切削实验中.试验结果表明面形误差补偿加工方法可以进一步消除加工误差,将非球面的面形精度PV值从微米级(1.23μm)提高到亚微米级(0.36μm)的程度,表面粗糙度R_a从亚微米级(0.27μm)改善到超亚微米级(0.04μm)的范围.