ANALYSIS AND MEASUREMENT FOR THE DYNAMIC ERRORS OF COORDINATE MEASURING MACHINES

The analysis and calculating method of dynamic errors of CMMs during probing are discussed.To relate the dynamic displacement errors with the dynamic rotational errors a method for obtaining the displacement errors at the probing position from dynamic rotational errors is presented.It is pointed out that the finite element method might be used for modeling dynamic errors.However,dynamic errors are difficult to be modeled so a combined practical and theoretical approach is needed.In addition,the dynamic errors are measured with inductive position sensors.

ERROR COMPENSATION OF COORDINATE MEASURING MACHINES WITH LOW STIFFNESS

A technique for compensating the errors of coordinate measuring machines (CMMs) with low stiffness is proposed. Some additional items related with the force deformation are introduced to the error compensation aquations. The research was carried on a moving colunm horizontal arm CMM. Experimental results show that both the effects of systematic components of error motions and force deformations are greatly reduced, which shows the effectiveness of proposed technique.

ASSESSING THE DYNAMIC ERRORS OF COORDINATE MEASURING MACHINES

The main factors affecting the dynamic errors of coordinate measuring machines are analyzed. It is pointed out that there are two main contributors to the dynamic errors: One is the rotation of the elements around the joints connected with air bearings and the other is the bending of the elements caused by the dynamic inertial forces. A method for obtaining the displacement errors at the probe position from dynamic rotational errors is presented. The dynamic rotational errors are measured with inductive position sensors and a laser interferometer. The theoretical and experimental results both show that during the process of fast probing, due to the dynamic inertial forces, there are not only large rotation of the elements around the joints connected with air bearings but also large bending of the weak elements themselves.

Geometric error measuring,modeling,and compensation for CNC machine tools:A review

Geometric error,mainly due to imperfect geometry and dimensions of machine components,is one of the major error sources of machine tools.Considering that geometric error has significant effects on the machining quality of manufactured parts,it has been a popular topic for academic and industrial research for many years.A great deal of research work has been carried out since the 1970s for solving the problem and improving the machining accuracy.Researchers have studied how to measure,detect,model,identify,reduce,and compensate the geometric errors.This paper presents a thorough review of the latest research activities and gives an overview of the state of the art in understanding changes in machine tool performance due to geometric errors.Recent advances in measuring the geometrical errors of machine tools are summarized,and different kinds of error identification methods of translational axes and rotation axes are illustrated respectively.Besides,volumetric geometric error modeling,tracing,and compensation techniques for five-axis machine tools are emphatically introduced.Finally,research challenges in order to improve the volumetric accuracy of machine tools are also highlighted.

A New Study to Compensate Dynamic Measuring Error of Serial Multiple Degree of Freedom（DOF） Strain Gauge Force Sensor

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Pre-Compensation for Continuous-Path Running Trajectory Error in High-Speed Machining of Parts with Varied Curvature Features

Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.

A Method for Identification and Compensation of Machining Errors of Digital Gear Tooth Surfaces

In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are analyzed directly from the real tooth surfaces.The topography data of the part are off-line measured in the post-process.A comparison is made between two models:CAD model of DGTS and virtual model of the physical measured surface.And a matching rule is given to determine these two surfaces in an appropriate fashion.The developed error estimation model creates a point-to-point map of the real surface to the theoretical surface in the normal direction.A“pre-calibration error compensation”strategy is presented.Through processing the results of the first trail cutting,the total compensation error is predicted and an imaginary digital tooth surface is reconstructed. The machining errors in the final manufactured surfaces are minimized by generating this imaginary surface.An example of ma- chining 2-D DGTS verifies the developed method.The research is of important theoretical and practical value to manufacture the DGTS and other digital conjugate surfaces.

A New Inertial Sensing System for Dynamic Measurement of Parallel Machines

One way to solve the problem of measurement precision caused by deformity for thermal expansion, friction and load etc is to use an inertial sensor to measure a change in the length of the rod on a parallel machine. However, the characteristic of dynamic measurement in the inertial sensing system and the effects of the machine＇s working environment, bias error, misalignment and wide band random noise in inertial measurement data results in the in-accuracy of system measurement. Therefore, on the basis of the measurement system a new inertial sensing system is proposed; the drifting of error is restrained with a method of inertial error correction and the system＇s position and the velocity state variables are predicted by the data fusion. After measuring the whole 300mm movement in an experiment, the analyses of the experimental result showed that the application of the new inertial sensing system can improve the positional accuracy about 61% and the movement precision more than 20%. Measurement results also showed that the application of the new inertial sensing system for dynamic measurement was a feasible method to improve the machine＇s dynamic positioning precision. And with the further improvement of the low-cost solid-stateacceleramenter technology, the application of the machine can take a higher position and make the speed dynamic accuracy possible.

基于在机测量的曲面共形电路3D打印误差补偿方法

基于3D打印技术制备曲面共形电路具有广阔的应用前景,然而,由于曲面基材加工误差和导电线路定位误差的影响,导致曲面电路3D打印头高度难以精确控制,进而影响打印精度。为此,本文以气动式直写打印为研究对象,提出了一种“在机测量+线路模型重构”的打印头高度误差补偿方法。设计了一种曲率自适应测量点选取方法,利用NURBS曲线反算法对测量数据进行重构,还原真实线路模型。通过生成真实线路的打印轨迹,替换原始理论打印轨迹,补偿了打印头高度误差。自主搭建了一套集成了在机测量系统的曲面共形电路3D打印平台,设计了直线、圆弧与NURBS自由曲线3种形状的线路,进行补偿前后电路打印的对比实验。结果表明,未进行补偿前,在线路曲率较大的地方,线路在基板上的波峰处会产生拉丝现象,波谷处会产生堆叠现象,而补偿后的导线线宽比较均匀;进一步对每条导线的电阻进行测量,发现各条线路补偿前的电阻值波动较大,补偿后的电路的电阻值均匀,且相较补偿前平均降低65.99%,最大电阻降幅达85.75%。

基于阿贝原则的机床主轴误差测量研究

机床测量是误差补偿的前提,分析主轴箱移动时产生的阿贝误差原因,给出主轴箱沿Z轴移动时X方向和Y方向的直线度误差,根据主轴箱直线度误差数据进行建模并给予补偿,结合具体的工程实例验证了阿贝误差补偿的有效性。

齿轮加工机床几何误差补偿研究综述

齿轮的加工精度是制约高端装备发展的关键瓶颈,高性能齿轮加工机床是实现齿轮高精度加工的选择。齿轮加工机床结构和运动的复杂性增加了其几何误差补偿的难度。通过分析近年来国内外多轴通用机床的几何误差补偿技术并结合齿轮加工机床几何误差补偿发展现状,对齿轮加工机床几何误差补偿技术展开综述,总结几何误差的来源,介绍多体系统理论、旋量理论、微分运动矩阵及变流理论4种可应用于几何误差建模的理论,分析采用激光干涉仪和球杆仪对直线轴及旋转轴进行几何误差测量与辨识的方法,概述通过NC数据修改对几何误差进行补偿的方法,为齿轮加工机床几何误差补偿设计提供参考。

三坐标测量机在精密加工中的误差补偿研究

三坐标测量精度对精密加工过程的质量控制有直接影响,研究三坐标测量误差模型与补偿方法,实现高精度测量对提升精密加工质量意义重大。分析了三坐标测量机的误差来源及分类,重点研究误差建模识别与补偿核心技术,并阐述误差补偿技术在航空航天、半导体集成电路、精密模具等领域中的实际应用情况。研究表明,当前的误差补偿技术可以有效提高三坐标测量机的重复性、重现性和绝对精度,为精密加工提供高效的质量检验与动态控制保障。

基于在机测量的薄壁叶片加工误差建模与补偿方法

薄壁叶片具备结构复杂、刚度弱、材料难加工等特性,且在加工过程中受到力导致变形、刀具磨损及机床精度演变等多源影响,造成其加工精度差、周期长。针对此问题,提出了基于在机测量的薄壁叶片加工误差建模与补偿方法,建立了基于机器学习的加工误差模型以及基于迭代系数的补偿值修正计算方法,开发了基于数控系统原点偏移功能的加工误差实时补偿系统,实现了复杂工况下薄壁叶片加工误差的在机检测、自动建模与实时补偿。薄壁叶片铣削加工验证试验结果表明,在机测量-补偿加工后的薄壁叶片无论是弹性变形为主的背部还是塑性变形为主的前部,其加工误差均得到较好的抑制,有效提高了其加工精度。

三坐标测量机辅助工装检测误差补偿策略研究

随着先进制造技术的迅猛发展,对零件精度的要求也在不断提升,而误差检测的准确性是确保零件精度的重要前提。在三坐标测量机的工作过程中,运动轴的几何误差会显著影响检测结果。为提高检测精度和效率,设计了一款用于三坐标测量机的辅助工装,并通过对主要运动方向进行微调,实现对工件检测误差的精准补偿。以齿轮误差检测为例,根据检测系统的拓扑结构,可以推导出Houston较低序号物体阵列,建立含工装和齿轮的几何误差传递模型。研究结果为检测误差补偿提供了理论依据,也为其他多轴运动的误差传递模型提供了参考。

直线加速器控制网测量跟踪仪测角误差标定

根据关键设备在直线加速器隧道内的布局,控制网布设在隧道地面和墙面。跟踪仪是直线加速器控制网测量的主要仪器,跟踪仪的测角误差是影响设备精度的关键因素。根据隧道墙面和地面网点的布局以及跟踪仪测量方案,对跟踪仪所有测量状态下的水平角和垂直角进行分解;然后通过高精度三坐标测量仪和跟踪仪联动测试,对分解后的角度进行高精度求解,解算值用于修正跟踪仪的实测角度。结果表明,不管是哪种测量状态,跟踪仪实测角度值均大于解算值;地面网点垂直角和水平角的偏差与跟踪仪的标称精度基本相当;墙面点水平角超过15°时,测角误差随着角度的增加而增大,在隧道控制网测量时需要对墙面点水平角进行修正。

基于在线测量的叶片误差变余量补偿研究

叶片是航空发动机中重要的零部件,叶片的加工成型质量对发动机实际工作时的安全性和效率影响巨大。本文基于在线测量结果,得到加工后叶片整体误差值,根据误差结果设计变余量补偿,通过NURBS曲线补偿对叶片余量进行重构从而补偿加工误差,然后通过对比实验分析补偿前后的加工效果。结果表明,补偿后有效改进了零件精度。在实验参数下,未经补偿的最大轮廓误差为0.057mm,经过补偿后轮廓误差为0.024mm,优化后的加工结果满足精度要求以及实际使用要求。

立铣刀磨削加工的棒料装夹偏差补偿技术

刀具棒料装夹偏差是影响刀具磨削精度不可忽视的重要因素。本文基于在机测量探测刀具棒料上各采样点位置的装夹偏差,建立了理论刀具刃线上点的偏差估算方法,在实际磨削加工时,将偏差值反向补偿至磨削轨迹,从而减小刀具的装夹偏差对刀具磨削精度的影响。通过试验磨削四刃平底刀和双刃球刀,在棒料装夹偏差较大的情况下,采用补偿的方式能够提高刀具外形磨削精度。

动态补偿下洁净室空气温湿度计测量误差自动控制

温湿度计受使用环境差异、设备老化损坏和人为操作失误等影响,测量误差较大,为此,提出动态补偿下的洁净室空气温湿度计测量误差自动控制方法。基于传播系数整合精密露点仪差异、温湿度箱湿度变化、重复测量温湿度计、温湿度计分辨力导致的温度、湿度测量误差数据,引入稳定性函数来描述最大允许温湿度误差的稳定特性,并将该函数作为控制装置的参考。建立温湿度传感器和控制装置之间的数学关系,基于数学关系设计一种适用于此问题的反滤波补偿器,采用递推方式进行周期性的测量误差参数校准与补偿过程,实现动态补偿控制。实验测试结果表明,经由所提方法控制后,可取得与实际结果非常接近的测量结果,将测量误差控制在非常小的范围内,确保温湿度计测量结果具有高精度。

差压式流量计精度范围分析及宽量程计量方法

随着我国工农业的发展,对流体流量的测量提出了越来越多的要求。特别是在天然能源不断减少的当下,节约能源、维持能源可持续发展已经成为国家发展的重中之重。因此,准确计量已经成为流量仪表的重要指标之一。差压流量计是一款传统的流量仪表,具有结构简单、无可动部件、可靠性高、稳定性好等特点,在各行业得到了广泛应用。差压装置本身的测量范围很大,但却因为多种因素影响,精度范围并没有达到理想的效果。该文根据差压式流量计的测量原理,分析不同因素对流量计流量测量范围及精度的影响,并为差压式流量计宽量程高精度的测量提供了设计及解决方法。

基于坐标测量机的圆度误差测量不确定度分析

测量圆度的仪器众多,如指示表、测微计、圆度仪、影像仪、坐标测量机等。坐标测量机因测量圆度精度高、效率高的特点而得到了广泛应用。测量不确定度作为评价测量结果质量的重要指标,其来源非常复杂,不仅与坐标测量机本身的精度有关,还与采样策略、被测工件、环境条件及数据处理方法等因素有关。本文主要针对坐标测量机的圆度误差进行测量不确定度分析。