光学非球面超精密切削的在位测量及补偿加工

开发一种采用接触式测头与电容式位移传感器相结合的在位测量装置及非球面测量与补偿加工软件,进行C3604黄铜球面及非球面的单点金刚石超精密切削加工,并开展在位测量及补偿加工试验。补偿加工后,经在位测量系统测量,球面面形精度PV达到231.4?nm,非球面面形精度PV达到206.3?nm;与离线测量结果比对,结果分别相差3.0?nm和7.0?nm,验证了在位测量系统测量的精确性和补偿加工的有效性。      

面向高速切削加工的数控编程技术研究

高速加工数控编程技术是高速加工研究的关键内容之一,它极为重要也非常复杂。针对高速切削加工的特点,提出了新的数控加工编程策略,深入分析了高速粗加工和精加工过程中走刀路径的优化。通过这样的优化科学地编出最优、最实际的高速铣削数控加工程序,充分发挥高速铣削加工的特长。从而缩短零件的生产工艺过程,增加切削余量的去除率,提高表面的加工精度。     

三坐标曲面数控加工的刀具轨迹研究

多坐标曲面加工是数控加工中的关键技术，而刀具轨迹的规划是数控编程的基础和关键。文章从提高曲面加工的精度和效率出发，推导和分析了走刀步长和切削行宽度的计算公式，提出了曲面数控加工编程时刀具轨迹规划的原则，并结合实例进行了轨迹验证。     

基于Powermill叶根盘铣刀体的高速数控加工

运用Powermill软件,对盘铣刀刀体进行数控加工研究,并对其加工刀具、加工参数以及数控程序进行优化调试,生成粗、精加工的走刀轨迹、实现在高速铣床上进行机夹式叶根盘铣刀体的数控加工,在保证产品精度的同时,提高了加工效率,降低了制造成本。     

自由曲面数控加工走刀方向的优化研究

走刀方向对数控加工的效率有重要影响，尤其对于多曲面拼接自由曲面不规则轮廓区域的数控加工。针对现有自由曲面数控加工过程走刀方向优化研究存在的问题，提出了基于曲面数控加工区域划分的走刀方向优化策略，建立了简化的刀具轨迹计算模型和加工时间模型，并用实例加以验证，取得了满意的效果。     

微透镜阵列慢刀伺服金刚石车削位置精度的研究

为了进一步提高超精密慢刀伺服车削微透镜阵列的加工精度,采用实验的方法,通过分组加工法加工了矩形口径微透镜阵列和六边形口径微透镜阵列,分析了不同微透镜口径对超精密慢刀伺服车削微透镜阵列的位置精度的影响。实验结果表明:六边形口径微透镜阵列的位置精度更好,且位置精度波动比矩形口径微透镜阵列要小,其整体位置精度范围为0.3～2.1 μm,第一圈位置精度范围为1.7～1.9 μm,第二圈位置精度范围为0.3～1.2 μm,中心透镜对四周的位置误差范围为1.5～2.1 μm。     

数控割字机轮廓误差的预测补偿控制

为降低高速高精度数控机床的加工轮廓误差,文章提出一种轮廓误差预测补偿方法,不仅在直线和曲线切割中进行轮廓半径误差补偿,还在尖角处进行刀半径补偿和位置跟踪误差补偿。以数控割字机为平台进行补偿方法验证,补偿后轮廓误差大幅度降低,充分证明该补偿方法对提高数控机床加工精度和加工效率的实用价值。     

大型双曲率蒙皮拉伸模高效数控加工技术

为了提高大型双曲率蒙皮拉伸模的加工效率,设计了一种优质高效的数控加工工艺。借助三维CAM软件,编制数控加工程序,合理排布粗加工、半精加工、精加工的刀具轨迹,生成数控机床专用NC代码。利用几何仿真软件,对NC代码进行仿真检查,避免撞刀、过切等意外情况的发生。最后,对拉伸模进行实际的切削加工,模具工作型面质量良好,加工精度符合设计图样要求,表明了此加工工艺的可行性,为大型双曲率蒙皮拉伸模的高效数控加工提供了一种工艺方案。     

自由曲面五坐标数控加工中几个关键问题的研究

自由曲面用平头立铣刀五坐标数控加工可以明显地提高切削效率和零件表面质量,但无干涉刀位产生一直是个难以解决的问题,本文对其中的几个关键问题进行了研究,导出了平头立铣刀的有效切削半径的一种计算方法,给出了自适应走刀步长度算法和切削行距的计算公式,最后给出了无干涉刀位生成方法,并用实例验证了方法的可行性,为提高加工效率和精度提供了有效途径。     

数控车削特殊表面的走刀方向确定

在使用数控车床加工过程中,经常会遇到跨象限圆弧表面的加工,虽然数控车床加工一般的圆弧表面时不产生形状误差,但在车削跨象限圆弧时,加工表面就会出现一些缺陷.通过合理安排数控车削刀具的走刀方向和走刀路线,可确保加工出符合理论要求的圆弧轮廓,达到零件的加工精度要求.     

大口径方形非球面镜的高效磨削技术研究

本文基于X/Y/Z三直线轴平面磨床,研究了圆弧砂轮应用于大口径方形非球面镜的平行磨削新技术,介绍了圆弧砂轮平行磨削的机理、重点解决了砂轮形状误差在线检测、元件面形误差在线检测与误差补偿等关键技术问题.以430 mm×430 mm非球面镜为样件,进行了多轮高效精密磨削工艺实验,面形精度PV均值为4.2μm,表面粗糙度约0...     

Profile error compensation approaches for parallel nanogrinding of aspherical mould inserts

This paper reports a parallel nanogrinding protocol for fabricating aspherical mould inserts. In the protocol, a preliminary grinding cycle was first employed, which significantly reduced the effect of the initial wheel geometry error on the ground profile accuracy. A new compensation approach was developed. The compensation used the ground profile measured from a Talysurf profilometer to modify the NC tool path for the next grinding cycle. The tool path was modified by offsetting the residual profile error along the normal direction of a grinding point, rather than in the horizontal direction commonly used in the conventional method. The performance of the developed method was evaluated by fabricating aspherical mould inserts on cemented tungsten carbide. The result indicated that the residual profile error after two grinding cycles was reduced to approximately 0.4 μm in PV, with average surface roughness of below 10 nm, which is more efficient than the conventional compensation process.     

聚晶金刚石微细球头铣刀刃磨工艺参数优化

针对直径为0.5 mm的聚晶金刚石(PCD)微细球头铣刀刃磨质量控制问题，基于六轴数控刀具磨床几何运动原理，建立PCD微细球头铣刀的砂轮刃磨运动数学模型，开展PCD刀具精密刃磨正交试验，研究刃磨工艺参数对主轴负载率、刀具前刀面表面粗糙度、刀具刃口钝圆半径的影响规律。结果表明:磨削速度对主轴负载率以及刀具前刀面表面粗糙度的影响最为显著，提高磨削速度有利于获得较好的刀面质量；磨削深度对刃口钝圆半径的影响最为显著，减小磨削深度有利于获得锋利的刃口形状。通过合理选择刃磨工艺，PCD微细铣刀直径误差小于4.0 μm，刀具钝圆半径为4.5 μm，刀具角度误差小于1°，无明显刃磨损伤缺陷。      

超硬磨料砂轮自动化复合修整机床CAM系统开发

为了使复合修整方法中的多种工艺更系统地整合,提高成形砂轮的修整效率,结合自主研制的激光–机械复合修整装备,开发一套CAM系统,可根据不同砂轮截面形状,自动规划多工艺、多修整策略下的修整轨迹,计算平面三轴联动修整刀路,自动生成加工代码,同时设计可视化界面仿真加工过程。对青铜结合剂金刚石砂轮进行修整试验,结果表明：该系统可在保证机床不发生碰撞和过切的情况下,生成激光粗修、半精修及机械精修的加工程序,大幅提高复合修整方法的编程效率,修整后的砂轮轮廓误差在9.1μm以内,圆跳动误差为6.1μm。     

Profile error compensation in ultra-precision grinding of aspheric surfaces with on-machine measurement

A compensation approach based on the on-machine measurement was developed for the grinding of tungsten carbide aspheric moulds. In this approach, the on-machine measurement was employed to eliminate the profile error caused by the re-installation of the workpiece. A new method was proposed to reconstruct the actual ground profile based on the measured profile data. The overall profile error after grinding was obtained by subtracting the target profile from the actual ground profile along normal direction and was then used to generate a new tool path for compensation grinding. The experimental results showed that after three compensation grinding cycles the aspheric surface had a profile accuracy of 177 nm (in PV) with a roughness of 1.7 nm (in R_a). The on-machine measurement was in excellent agreement with the off-machine measurement by commercially available profilometers.     

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.     

Wheel curve generation error of aspheric microgrinding in parallel grinding method

In aspheric grinding of hard brittle material, in-process wheel wear is a crucial factor affecting the profile error of the ground surface. To suppress wheel wear, parallel grinding is adopted. Since the wheel and workpiece contact point changes during parallel grinding, geometric wheel error influences machining accuracy significantly. In the wheel truing process with a cup truer, the wheel radius is determined by the angle and distance between the wheel and the truer. Through geometric analysis, this paper presents a new equation of wheel radius, which enables process parameters, such as setup error or thermal error, to be determined easily. Simulation results show that wheel radius error is predominantly affected by vertical deviation between the wheel rotation center and the truer center. Experimental results show that wheel radius errors match those from simulation well.     

Design of a six-axis high precision machine tool and its application in machining aspherical optical mirrors

The paper presents the design of a six-axis machining system and its application in fabricating large off-axis aspherical mirrors with sub-aperture lapping techniques. The new system is based on computer-controlled optical surfacing (CCOS), which combines the faculties of grinding, polishing, and on-machine profile measuring, has the features of conventional loose abrasive machining with the characteristics of a tool having multiple degrees of freedom moving in planar model. And a novel dual touch-trigger probe profiler is designed, which is composed of a probe, model METRO-MT60 made by HEIDENHAIN Co., is integrated into the system for measuring the shape accuracy of the tested aspherical surface, another probe modeled METRO-MT12 is designed as a calibrating device for minimizing the cosine error caused by assembly inaccuracy. The new CNC machining system with two kinds of moving coordinate systems, dual tool activities and on-machine measuring is presently developed based on the new concept. The general material removal function during machining is analyzed on the basis of the Preston hypothesis. Further, an alignment test of the measuring profiler is carried out using a leveling rule as a specimen. The accuracy of the optical surfaces measured by the dual probe profiler is found to be within 1 μm PV after removing cosine error and error compensating, achieves to the resolving power of the profiler is about 0.2–0.5 μm, so the developed system can be applied to the shape accuracy measuring of aspheric fabrication with micro precision during fine grinding process according to the calibrating results. Finally, the manufacturing experiments are carried out by virtue of an off-axis oblate ellipsoid mirror with rectangular aperture as 770 mm×210 mm and centered 127 mm. The accuracy of the aspherical mirror improved from the initial form error of 17.648 μm rms to the final one of 0.728 μm rms after grinding for 200 h.     

磁流变抛光非球柱面镜的新工艺

高精密的柱面镜光学元件,不但要求其具有极低的表面粗糙度、无表面/亚表面损伤和低的残余应力等,而且需要保证其柱面母线的平行度与垂直度。通过分析传统磨研抛技术和计算机控制的光学表面成型技术(CCOS) 2种技术对柱面镜加工后的表面粗糙度、面形精度和母线误差的影响,归纳2种加工方法的优缺点,针对现有加工方法存在的低效率、高粗糙度、表面/亚表面损伤等问题提出一种具有对称结构的非球柱面镜磁流变抛光新工艺,并通过时间参数实验验证了新工艺的可行性。该工艺降低了柱面镜的表面粗糙度,提高了面型精度,在抛光时间为40 min时,表面粗糙度R_a从1.84 μm降低至0.36 μm,局部面型精度RMS₁从 1.91 μm降低到0.24 μm,母线截面面型精度RMS₂从4.1 μm下降到0.68 μm。      

Nano-precision measurement of diamond tool edge radius for wafer fabrication

In this paper, a non-destructive nano-precision measurement method for diamond tool cutting edge radius is presented. The basis of the method is that the profile of a tool cutting edge can be copied by indenting the tool cutting edge into the surface of a selected material, and that the copy of the profile can be measured at nano-precision level using AFM. The selected material elastic error compensation coefficient has to be determined to cancel out the effect of elastic spring-back. Copper was selected as the indentation piece material due to its (1) high rigidity and high density, (2) large Young’s modulus and (3) low yield strength. The elastic error compensation coefficient for the copper material is determined through the indentation of a tungsten carbide tool edge on the copper surface. By comparing the actual tool edge radius measured using scanning electron microscope (SEM) on the sectional view of the tungsten carbide tool with the one measured from the copied profile of the tool edge on the copper surface, the coefficient is obtained. Three diamond tool edge radii were obtained using the proposed method. Analysis is given for the accuracy of the proposed method, showing that as far as the error elastic compensation coefficient is consistent with the copper material used, the only source of errors with the measurement will come from the device for measuring the indented profile on the surface.