圆弧金刚石砂轮的修形及修锐技术研究

针对圆弧金刚石砂轮加工非轴对称非球面的平行磨削法中砂轮的修形精度要求较高，通常使用的水平圆弧杯状砂轮修整器很难保证加工精度的问题，提出带倾角圆弧修整器的设计方法。通过对修整器接触弧长的计算，修形延后率设计和修形补偿方法的研究及实验表明：新型圆弧修整器可满足高精度非轴对称非球面加工的要求。     

圆弧金刚石砂轮三维几何形貌的在位检测和误差评价

针对非球面光学元件加工对圆弧金刚石砂轮形状误差测量的需求,提出了砂轮三维几何形貌在位检测与误差评价方法。建立了砂轮外圆面螺旋扫描轨迹测量数学模型,利用位移传感器获取了砂轮表面轮廓数据;对得到的数据匀滑滤波后沿圆周展开并进行插值处理,得到砂轮三维几何形貌。然后,根据非球面平行磨削加工特点,提出评价圆弧砂轮形状精度的指标。通过提取三维几何形貌轴截面轮廓,进行最小二乘圆弧拟合得到不同相位处的圆弧半径与圆心坐标,并由误差分离获得砂轮表面圆弧的圆度误差、圆周跳动误差及轮廓圆心轴向偏差。最后,对非球面加工圆弧金刚石砂轮进行检测,获得了砂轮的三维几何形貌以及多个关键尺寸及其误差数据:即圆弧金刚石砂轮的平均圆弧半径为55.442 3mm,半径波动极差为0.16mm,中央±8mm环带内圆弧的圆度误差约为5μm,圆周跳动误差约为2μm,截面轮廓圆心轴向位置相对偏差为0.008mm。根据检测结果,进行了大口径复杂非球面磨削实验,得到的元件面形P-V值为4.62μm,RMS值优于0.7μm,满足工程的实际需求。     

砂轮几何参数对非球面轨迹包络磨削的影响研究

针对非球面轨迹包络磨削过程中砂轮磨损而影响加工质量的问题,根据非球面轨迹包络磨削成形原理,分析了轴对称非球面、非轴对称非球面加工中盘形砂轮的几何参数对轨迹包络磨削加工过程的影响。分析结果表明:盘形砂轮圆弧截面的圆弧直径、砂轮宽度、砂轮直径等几何参数将直接影响到参与磨削的砂轮磨粒的数量。合理选择盘形砂轮的几何参数,可以有效地增加参与磨削的砂轮磨粒数量,从而减少盘形砂轮的磨损,这对于提高非球面轨迹包络磨削加工精度有着非常重要的意义。     

树脂基圆弧金刚石砂轮的在位精密成形修整技术

针对球面、非球面及自由曲面超精密磨削加工用树脂基圆弧形金刚石砂轮难以精密修整的问题,提出基于旋转绿碳化硅(GC)磨棒的在位精密成形修整技术。在分析GC磨棒和圆弧砂轮几何关系的基础上,确定修整过程中圆弧插补轨迹的补偿方法及GC磨棒运动轨迹的设计方案。采用KEYENCE激光测微仪采集砂轮圆弧特征点,表征圆弧砂轮的修整状况。研究不同粒度的GC磨棒、进给深度和圆弧插补速度对圆弧金刚石砂轮修整率和修整精度的影响规律。研究结果表明,该修整方法可根据加工曲率半径要求实现不同圆弧半径砂轮的精密在位修整,修整后可自动消除砂轮垂直方向的位置偏差;采用400#和800#的GC磨棒对D3和D7砂轮均有较高的修整率(0.7~6.7);与400#和1500#的GC磨棒相比,800#GC磨棒更适合粒度为D3和D7圆弧金刚石砂轮的精密修整;相比圆弧插补速度,进给深度对砂轮的圆弧半径尺寸误差和形状误差影响更大,进给深度越小,圆弧半径尺寸误差和形状误差越小;修整后两种砂轮的圆弧半径误差均可控制在5%以内,D3砂轮的形状误差可控制在3μm/4 mm以内,D7金刚石砂轮可控制在6μm/4 mm以内,修整后比修整前形状误差提高14倍左右。     

高精度非球面制造系统控制软件的设计

根据高精度非球面制造及测量的需求,设计并实现了高精度非球面制造及测量系统的控制软件。系统基于工控PC机和Windows98操作系统,并选用Delphi 6.0和Visual Fortran作为开发工具。系统采用在线误差补偿加工技术,可选择平面砂轮和圆弧砂轮两种加工方式,达到加工高精度光学非球面镜的要求。     

微小非球面光学模具单点斜轴误差补偿磨削

针对微小非球面光学透镜模具的纳米单点斜轴误差补偿磨削进行研究。通过分析比较传统的直交轴磨削法,提出微小非曲面光学模具的单点斜轴磨削方式,有效避免微细砂轮在加工微小非球面时发生干涉情况;采用单点恒定磨削方式提高微小非球面磨削的稳定性及精度。通过分析磨削区域内微细砂轮与微小非球面的干涉情况,从而合理计算并选用较高强度的微细砂轮。提出微小非球面误差补偿磨削策略,分析砂轮的对心误差(x轴向和y轴向)对形状精度的影响,采用法向残余误差补偿的方法对加工后的形状误差进行超精密补偿磨削。利用超精密磨床对口径为2 mm的超硬热压模具碳化钨材料的微小非球面进行纳米单点斜轴误差补偿磨削试验,经过三次超精密磨削及误差补偿循环,其形状精度PV从1 034 nm改善至146 nm,表面粗糙度达到Ra2.19 nm。     

大尺寸轴对称非球面磨削精度建模和分析

运用刚体运动学理论和坐标变换,建立高精度平面磨床的通用误差模型。针对大尺寸轴对称非球面工件的高精度加工要求,采用光栅式平行磨削的加工方式。根据这种非球面磨削方式和高精度平面磨床的结构,给出影响大尺寸非球面加工精度的主要误差因素,并建立基于这些主要误差因素的大尺寸非球面误差模型。对主要单项误差的分析表明,磨床的直线度及定位精度误差和圆弧半径误差是影响面形分布的主要因素,而面形误差值则是各个误差综合作用的结果。通过误差模型可以预测面形误差分布和大小,并可以利用该模型进行补偿加工。加工试验结果表明,该模型能够比较准确地预测面形精度,补偿试验后精度提高,说明利用该模型进行补偿是有效的。     

轴对称非球面加工误差分离及补偿技术

分析轴对称非球面磨削加工中砂轮尺寸精度和形状精度等因素对加工工件精度的影响,提出适用于非球面加工的工件表面误差多参数分步分离的数学模型。新方法解决了原有加工存在的系统误差分离不彻底、补偿加工所需要的各项参数难确定等问题。试验结果表明：该数学模型更接近于理论计算轨迹,可以有效地减小加工误差,进一步提高工件的加工精度。     

基于多体系统理论的非球面磨削误差模型与补偿技术

为提高大中型非球面的磨削精度,从而提高非球面的加工效率,研究轴对称非球面磨削过程的误差模型,并对误差进行补偿.运用多体系统理论,基于一阶线性模型,建立非球面磨削成形的统一误差模型,并且推导各种误差对于最终面形误差的传递函数.基于传递函数特征相似误差集中补偿的方法,将所有趋势项误差转化为砂轮对刀误差以及砂轮形状误差进行补偿,并建立实用补偿模型,从而避免求解、校正各项具体误差.试验结果表明,建立的误差模型和辨识模型正确,可以使面形误差收敛到预期范围,从而解决了轴对称非球面磨削中的精度控制问题.     

电火花机械磨削修整粗粒度成形砂轮试验研究

粗粒度金属基金刚石砂轮磨削效率高,面形精度保持性好,可以满足各种成形零件的精密加工,但存在因修整困难而难以推广的问题。针对该问题,提出采用电火花机械磨削法修整粗粒度金刚石砂轮。探究了放电参数对修整效率及刀具损耗量的影响规律,并以修整效率为优化目标选取粗修整试验放电参数,以修整精度为优化目标选取精修整试验放电参数。设计了半径为3 mm的凹圆弧、凸圆弧砂轮修整试验,粗修整后凹圆弧、凸圆弧半径分别为2867.510μm、2919.254μm,尺寸误差分别为4.43%、2.69%,轮廓精度PV值为54.34μm;精修整后凹圆弧、凸圆弧半径分别为3005.107μm、3001.588μm,尺寸误差分别为0.17%、0.053%,轮廓精度PV值为17.28μm。最后,磨削碳化硅陶瓷试件,获得凹圆弧、凸圆弧半径的尺寸误差分别为0.24%、0.045%,工件表面粗糙度Ra可达0.463μm。     

RESEARCH ON PARALLEL GRINDING METHOD OF NON-AXISYMMETRIC ASPHERIC LENS

In order to resolve the problems of machining non-axisymmetric aspheric lens, which is short of flexibility in mould grinding and needs high accuracy CNC machine center in globe diamond wheel grinding, a new parallel grinding method that utilizes common arc diamond wheel is put forward. Base on the approach calculation of machining locus, the advantages of parallel grinding that machines non-axisymmetric aspheric lens by 2.5-axis CNC machine center have been obtained. The results of grinding experiment show the new method can meet the need of grinding high accuracy non-axisymmetric aspheric lens.     

RESEARCH ON PARALLEL GRINDING METHOD OF NON-AXlSYMMETRIC ASPHERIC LENS

In order to resolve the problems of machining non-axisymmetric aspheric lens,which is short of flexibility in mould grinding and needs high accuracy CNC machine center in globe diamond wheel grinding,a new parallel grinding method that utilizes common arc diamond wheel is put forward.Base on the approach calculation of machining locus,the advantages of parallel grinding that machines non-axisymmetric aspheric lens by 2.5-axis CNC machine center have been obtained.The results of grinding experiment show the new method can meet the need of grinding high accuracy non-axisymmetric aspheric lens.     

Critical success factors for Kaizen implementation in manufacturing industries in Mexico

To machine a noncoaxial nonaxisymmetric aspheric lens, a new parallel grinding method that employs a fixture with an adjustable gradient (AGF) is proposed. The AGF is developed for a three-axis computer numerically controlled grinding machine. The grinding method is presented according to the proposed grinding system. To ensure the machining accuracy, the main machining errors and the compensation algorithm are discussed for the grinding method using the AGF. Simulation results show that the AGF rotation errors are crucial factors affecting the profile error of the machined workpiece. Experimental results show that employing the compensation algorithm increases machining accuracy.     

Fabrication of small aspheric moulds using single point inclined axis grinding

Single point inclined axis grinding techniques, including the wheel setting, wheel–workpiece interference, error source determination and compensation approaches, were studied to fabricate small aspheric moulds of high profile accuracy. The interference of a cylindrical grinding wheel with the workpiece was analysed and the criteria for selection of wheel geometry for avoiding the interference was proposed. The grinding process was performed with compensation focused on two major error sources, wheel setting error and wheel wear. The grinding results showed that the compensation approach was efficient and the developed grinding process was capable to generate small aspheric concave surfaces on tungsten carbide material with a profile error of smaller than 200 nm in PV value after two to three compensation cycles.     

小口径非球面斜轴磨削及磁流变抛光组合加工工艺及装备技术研究

为提高小口径非球面模具加工效率和加工精度,提出一种结合斜轴超精密磨削和斜轴磁流变抛光的组合加工方法,将两种超精密加工方法集成在一台机床上,以缩短装夹时间以及降低装夹误差。研制新型的小口径非球面超精密复合加工机床,对直径Ф6.6 mm的非球面碳化钨模具进行了加工试验。斜轴磨削后加工表面粗糙度达到R_a 6.8 nm,斜轴磁流变抛光后表面粗糙度达到R_a 0.7 nm,面型精度可以达到PV 221 nm。结果表明,所开发的小口径非球面超精密复合加工装备能达到加工要求,可有效提高加工精度和加工效率。     

Research on the error analysis and compensation for the precision grinding of large aspheric mirror surface

The purpose of this paper is to propose a compensation grinding method for large aspheric mirror surface. Because the tradition grinding is not suitable for large aspheric mirror surface, in this paper, a grate parallel grinding in 3-axis and an on-machine measurement system are applied. Based on that, it presents the errors that mainly affect the form accuracy and technology of compensation grinding. An experiment of compensation grinding was carried out for large aspheric mirror surface. With the separation of decentering, wheel arc, and residual grinding system error, the PV value further decreased comparing to tradition compensation. These results indicated that this compensation can improve the form accuracy significantly in large aspheric mirror surface grinding.     

Form error compensation in single-point inclined axis nanogrinding for small aspheric insert

Based on an examination of traditional arc-enveloped grinding method, a single-point inclined axis nanogrinding method is presented to grind an aspheric insert by compensating tool setting error, radius error, and residual form error. Profile data from on-machine measurement are used to obtain the tool setting error and radius error of grinding wheel, as well as the normal residual form error. Compensation method of single-point inclined axis nanogrinding is built up for generating new compensation path. Grinding test of aspheric tungsten carbide insert with diameter 9.5 mm is conducted to evaluate performances of the grinding mode and compensation method. A last form error of 200 nm in peak to valley and surface roughness of 2.243 nm in Ra are achieved. These results indicated that the form error compensation method and single-point inclined axis nanogrinding mode can significantly improve form accuracy and surface roughness of ground surface.     

离轴楔形非球面平行磨削及补偿技术研究

针对精密光学系统中对高精度离轴楔形非球面透镜的加工要求,提出采用由倾角可调三轴摆动式数控夹具系统和精密磨床数控系统(Computer numerical control,CNC)协调完成离轴楔形非球面透镜的高效加工方法。设计三轴摆动式数控夹具机构及控制系统相关程序,完成夹具制造及调整,在数控精密平面磨床上实现对离轴楔形非球面平行磨削加工。倾角可调夹具的设计简化原有的加工工序,提高加工效率。根据平行磨削加工原理对加工插补误差和工件形面误差进行模拟计算,结果表明:夹具旋转误差以及工件的形状尺寸会对加工精度产生较大影响。根据模拟结果和平行磨削方法原理,设计工件加工误差的在位补偿方法。通过平行磨削加工及补偿试验证明:在位补偿方法可以有效提高工件的加工精度。