蒙皮铣削镜像顶撑技术研究

通过分析飞机蒙皮零件的结构特性、加工难点以及传统蒙皮加工方法的缺陷,介绍了满足新一代蒙皮零件加工精度需求及绿色制造发展趋势的新型蒙皮加工技术、蒙皮镜像铣削技术。蒙皮镜像铣技术是集减薄、切边、开口、钻孔于一体化的多功能铣削技术。本章通过阐述蒙皮镜像数控编程、刀轨自适应调整及厚度精确控制3个关键技术详细介绍了蒙皮镜像铣加工工艺。通过加工、检测、监测的有效集成精确控制蒙皮加工厚度及变形,在提高加工效率的同时,保证加工质量,降低加工成本。     

蒙皮镜像铣切系统及先进制造工艺的应用

针对飞机蒙皮零件传统工艺方法无法满足精确制造和绿色制造的需求,对数铣替代化铣的飞机蒙皮厚度精确加工技术进行研究,采用集蒙皮切边、开口、制孔和厚度精确加工于一体的蒙皮镜像铣切系统,实现了飞机蒙皮的精确制造.介绍了国内首台蒙皮镜像铣切设备的系统工作原理及应用状况,对比分析了传统工艺方法与蒙皮镜像铣切系统先进制造工艺及数字化柔性工装技术的优势.通过实际应用验证:蒙皮一体化加工技术的应用使我国航空制造技术迈入了飞机蒙皮精确一体化制造领域,推动了我国航空制造技术的发展.     

蒙皮镜像铣切系统及制造工艺的应用研究

传统蒙皮结构化铣工艺存在周转周期长、污染程度高、精度控制不佳等问题。镜像铣切系统因可以较好地解决这些问题,已成为主要的飞机蒙皮加工工具。简单阐述蒙皮镜像铣切系统的构成,讨论蒙皮镜像铣切系统相关技术工艺,如减薄技术、镜像铣支撑技术,从加工零件、装夹工艺、专用刀具以及区域特别处理的角度出发,分析蒙皮镜像铣切加工系统的工艺策略。     

飞机蒙皮镜像铣切加工工艺策略分析

首先介绍了镜像铣加工系统及其两种零件装夹方式，然后分析了零件加工质量控制指标，最后针对边缘夹持式镜像铣，从加工零件的选择、零件装夹策略、刀具选择及蒙皮铣切策略规划4个方面分析讨论了飞机蒙皮镜像铣切加工工艺策略，并提出了相应的指导意见。     

铝合金蒙皮化铣保护层切割技术及工具

为了解决铝合金蒙皮化铣保护层切割效率低、质量差的问题,进行了系统的铝合金蒙皮化铣保护层切割方法及工具技术研究,研制出优质高效的铝合金蒙皮化铣保护层切割工具,并通过系统的加工试验优化了工具的结构及其结构参数,提高了铝合金化铣保护层切割的效率与质量,降低了飞机的制造成本及其制造周期。     

基于非参数误差模型的镜像铣同步精度补偿

针对薄壁件镜像铣加工过程中,铣削侧和支撑侧的相对位置和方向误差严重影响工件加工精度的问题,提出一种由误差预测模型和误差补偿策略组成的同步运动精度补偿算法。误差预测过程应用了一种基于形函数的插值算法,能够预测镜像铣工作空间中任意期望位置的相对位置和方向误差。误差补偿过程将铣削侧的刀位作为参考,对支撑侧的刀位进行补偿,然后分别生成数控(NC)代码。经过加工测量实验,补偿后的相对位置和方向精度分别提高了73%和60%,验证了所提算法的有效性。     

飞机蒙皮加工工艺

介绍了飞机蒙皮的外形、材料及加工性能,论述了飞机蒙皮加工的技术要求,分析了飞机蒙皮的加工工艺,同时给出了飞机蒙皮镜像铣削系统和机器人制孔技术的特点。     

薄壁叶片侧铣变形误差补偿及刀位规划研究

刀位规划中的原理性误差和加工过程中的变形误差,是薄壁叶片侧铣加工时最重要的误差来源。通过变形误差建模分析,将其引入侧铣加工刀具路径优化模型,提出了一种侧铣变形误差补偿及刀位规划的新方法。该方法适用于直纹面和类直纹面薄壁叶片侧铣加工,并能生成综合误差最小的刀具路径轨迹。仿真实例表明,相对于传统的刀位规划-变形补偿策略,该方法计算出的误差更加准确有效,从而提升了侧铣加工刀位规划的效率和可靠性。     

镜像铣支撑端与铣削端之间的碰撞检测算法研究

双五轴镜像铣机床是提高蒙皮、壁板等大型薄壁件加工质量的新型设备,铣削端与支撑端均采用卧式龙门五轴结构,且镜像分布于加工工件两侧。在加工过程中,铣削端与支撑端同步运动,因此它们之间的碰撞检测是实现安全、稳定加工的保障。采用基于包围球的AABB包围盒模型与GJK算法,分别建立了双五轴镜像铣设备的运动模型以及防碰撞算法。首先,通过分析AABB包围盒和包围球的优缺点,提出一种将AABB包围盒与包围球相结合的包围体,从而建立支撑端和铣削端的全尺寸模型;其次,分析包围盒碰撞检测方法与GJK算法的特点,给出双五轴镜像铣防碰撞算法;最后,使用OpenGL对建立的模型与防碰撞算法进行仿真验证,结果表明该模型与算法是有效的。     

三轴义齿雕铣机空间误差解耦与补偿研究

针对三轴义齿雕铣机在加工过程中存在空间误差较大、加工精度较低等缺点,提出了一种对空间误差实施解析与补偿的新方法。首先分析机床拓扑结构,利用多体系统理论确定机床低序体阵列和运动学约束链,建立空间误差模型。然后对三轴雕铣机的各项几何误差进行测量并求解其空间误差值,分别计算各项几何误差相对于机床空间误差的相关性系数,以辨识对空间精度影响较大的重要几何误差分量。最后利用线性回归模型建立空间误差与位置的隐射函数,以便建立空间误差补偿模型。以z轴为例,对所建立的误差补偿模型进行实验验证。结果表明通过补偿后z轴空间误差从1. 26 mm降低到0. 735 mm,降幅为41. 7%,义齿加工精度得到了有效的提高,可见该方法有一定的实用价值。     

A Novel Method of Efficient Machining Error Compensation Based on NURBS Surface Control Points Reconstruction

A novel method to improve the efficiency of error compensation in free-form surface machining based on the Non-Uniform Rational B-Splines (NURBS) surface control points reconstruction is proposed in this article. With the presented method, a relatively small number of inspection points are needed to be measured for error compensation. The machined surface is obtained by reconstructing the control points of the designed surface based on the on-machine measurement data. The machining error of the surface is obtained by calculating the difference between the machined surface and the designed one. Then a compensate surface is achieved using the mirror symmetry model and surface modification method to compensate the machining error. Experimental validation for the milling of a NURBS surface shows that the machining accuracy of the surface is improved by 62.57% through use of the proposed method.     

基于奇异避免的薄壁件镜像铣削加工路径优化

在双五轴镜像铣削加工中,由于旋转轴运动突变带来的奇异问题,导致薄壁件表面加工质量以及加工效率降低。在分析奇异问题产生原因的基础上,提出一种奇异区域加工路径优化的方法。基于C-空间的概念,在奇异区域边界约束条件下,同时满足镜像铣削加工中刀轴矢量与工件表面保持垂直,以最小刀轴矢量距离确定备选刀轴矢量,对奇异区域的刀轴矢量进行局部修正。然后对整条加工路径进行B样条曲线拟合,基于最小参数曲线应变能建立优化模型,通过对参数曲线的调整,提高路径的光顺性,保证加工效率,提高加工质量。最后,通过仿真实验和实际加工结果验证所提方法的有效性。研究结果表明,最小壁厚误差减小50%,最大壁厚误差减小75%,整体壁厚误差范围缩小了68.75%,同时完整的路径加工时间缩短了2.1%。     

SOFTWARE-CONTROLLED SYSTEM OF ULTRA-PRECISION MACHINING AXISYMMETRIC ASPHERIC MIRROR

In order to improve machining accuracy and efficiency, a software-controlled system of ultra-precision machining for axisymmetric aspheric mirror, using techniques of error compensation, remote transmission and modularization, is designed based on industrial PC, Windows 2000 work platform and Visual Basic 6.0. By experiments, this system realizes functions of ultra-precision machining, machining error compensation, remote data transmission and automatic data transformation among first machining, compensation machining and accuracy measurement. The actual application shows that error compensation improves machining accuracy, remote transmission improves machining efficiency while modularization avoids repeated work and improves design efficiency. Therefore, the system has met ultra-precision machining need for aspheric mirror.     

Neural network-based modelling and error compensation of thermally-induced spindle errors

This research is concerned with enhancing the accuracy of a machining centre by compensating for thermally induced spindle errors in real-time. A neural network model was developed for on-line thermal error monitoring. A PC-based error compensation scheme was also developed to upgrade a commercial CNC controller for real-time thermal error compensation without any hardware modifications to the machine. The spindle thermal errors of a vertical machining centre were reduced by 70% after compensation.     

An integrated error compensation method based on on-machine measurement for thin web parts machining

Thin webs are widely used in the aerospace industry for the advantages of compact structure, light weight and high strength-to-weight ratio. Due to its low rigidity, serious machining error may occur, therefore, Finite Element method and mechanism analysis are usually utilized to modeling its deformation. However, they are very time-consuming and only suitable for elastic deformation error. In this study, an integrated error compensation method is proposed based on on-machine measurement (OMM) inspection and error compensation. The OMM inspection is firstly applied to measure the comprehensive machining errors. The Hampel filtering is then used to eliminate outliers, followed by the triangulation-based cubic interpolation as well as a machine learning algorithm which are used to establish the compensation model. At last, the real time compensation of high-density cutting points is realized by developing the compensation system based on External Machine Zero Point Shift (EMZPS) function of machine tool. Three sets of machining experiment of a typical thin web part are conducted to validate the feasibility and efficiency of the proposed method. Experiment results revealed that after compensation, the comprehensive machining errors were controlled under different machining conditions and 58.1%, 68.4% and 62.6% of the machining error ranges were decreased, respectively. This method demonstrates immense potential for further applications in efficiency and accuracy improvement of thin-walled surface parts.     

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.     

A real time machining error compensation method based on dynamic features for cutting force induced elastic deformation in flank milling

During the machining process, cutting forces cause deformation of thin-walled parts and cutting tools because of their low rigidity. Such deformation can lead to undercut and may result in defective parts. Since there are various unexpected factors that affect cutting forces during the machining process, the error compensation of cutting force induced deformation is deemed to be a very difficult issue. In order to address this challenge, this article proposes a novel real time deformation error compensation method based on dynamic features. A dynamic feature model is established for the evaluation of feature rigidity as well as the association between geometric information and real time cutting force information. Then the deformations are calculated based on the dynamic feature model. Eventually, the machining error compensation for elastic deformation is realized based on Function Blocks. A thin-walled feature is used as an example to validate the proposed approach. Machining experiment results show that the errors of calculated deformation with the monitored deformation is less than 10%, and the thickness errors were between ?0.05 mm and +0.06 mm, which can well satisfy the accuracy requirement of structural parts by NC (Numerical Control) machining.     

加工中心在线检测误差补偿技术研究

提出了加工中心在线检测误差通用数学模型,研究了测量系统误差参数辨识方法,实现了基于模型的加工中心在线检测软件误差补偿。对标准试件的检测及补偿结果表明,补偿后加工中心检测精度提高５３．８％以上,加工中心在线检测误差补偿实验结果证明了提出的误差补偿方法的可行性和有效性。     

非球面镜超精密加工系统控制软件的研究

针对非球面镜超精密加工的需要,设计了基于工控PC机和Windows2000操作系统、选用VB作为开发工具及远程传输技术,实现非球面镜超精密加工、加工误差补偿及远程数据传输等多项功能的软件控制系统.系统采用模块化设计技术,可实现初加工,补偿加工和精密测量之间数据的自动转化,满足了超精密非球面镜加工精度的要求.     

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。