数控加工刀具变形误差补偿技术研究

在数控铣削加工的研究中,刀具变形引起的加工误差对工件的加工精度影响较大.研究了一种考虑切屑厚度影响的切削力模型,建立了由切削力引起的刀具变形加工误差的分析模型.为了提高加工精度,提出了一种线性迭代误差补偿算法,方法主要对由切削力引起的刀具变形产生的切削误差进行循环迭代补偿.通过应用数控加工中心,方案进行了验证,对补偿后...     

大型龙门导轨磨床工作台运动精度控制方法研究

大型龙门导轨磨床工作台整机运动场、主轴漂移量、补偿误差均会对控制精度产生影响,因此研究新的大型龙门导轨磨床工作台运动精度控制方法;根据大型龙门导轨磨床基本结构连接形态,求解主要技术参数,实现龙门导轨磨床工作台设计;从静态、动态两个角度出发,分析立柱部件、横梁部件受力情况,确定多目标拓扑与模态有限元条件,以此分析磨床工作台的运动特性;以动静态参数求解结果和整机运动场为基础,计算主轴漂移量的取值范围,结合相关运动参数计算补偿误差数值,结合对补偿误差数值计算以及PDDF控制器结果对工作台运动精度进行控制;实验结果表明,所提方法可以将工作台运动路径拟合误差控制在0～0.07 mm范围之内,满足龙门导轨磨床工作台运动精准控制的要求,实际应用效果好。     

立式数控铣削刀具半径补偿功能的运用

在数控铣床零件加工过程中,由于刀具的磨损、现场实际刀具尺寸与编程时规定的刀具尺寸不一致和更换刀具等原因,都会直接影响最终加工尺寸,造成加工误差.为了最大限度地减少因刀具尺寸变化等原因造成的误差,目前数控铣床通常都具有刀具半径补偿功能,根据输入的修正补偿量和程序自动地加工出优质零件,否则,很难保订加工精度.同时,使用刀具半径补偿,实现了根据零件轮廓直接编程的巨变,大大简化了编程工作量.冈此,理解刀具半径补偿并能正确灵活地使用刀具补偿功能,将起到事半功倍的效果,将刀具补偿和变量编柞结合使用,还可实现一些复杂曲面的加工,在数控切削加工中有较强的实用价值.     

网络化测试系统中时滞误差的动态补偿

以基于网络的动态测试为研究背景,在无GPS等时钟同步设备的条件下,设计一个基于LMS算法的自适应估计器,对参比系统、被测系统及误差处理器的时钟源同步误差进行在线估计,实现了对网络时延引起的时滞误差的动态补偿。仿真结果表明,该自适应时延估计器能够有效地对时钟源同步误差进行估计,网络化测试系统动态补偿后的总误差比补偿前下降了85％。     

五轴侧铣加工空间刀具半径补偿算法的研究

根据五轴数控侧铣加工主要依靠刀轴矢量姿态变化来完成的特点,对侧铣加工中的刀具半径补偿问题进行研究,提出了一种补偿方法.该方法应用在工件坐标系下,与具体的机床类型无关,充分考虑刀轴矢量可变的各种加工情形.算法包括一个加工块内的半径补偿、拐角类型的判别公式、内拐角和外拐角处的过渡处理方法.文中对补偿方法进行了误差理论分析,并结合加工实例在matlab中进行了仿真实验,实验结果显示补偿算法能够满足系统加工的精度要求.     

刀具半径补偿常见错误及问题分析

数控加工具有加工精度高、效率高和质量稳定等特点,而合理掌握刀具补偿方法,灵活应用刀具补偿功能,合理设置刀具半径补偿值,是保证精度和质量稳定的重要因素.但是在数控编程加工编程的过程中,还经常出现一些刀具半径补偿功能应用上的错误,因此,有必要对数控加工的刀具半径补偿方法进行探讨.     

对数控铣削加工中刀具补偿的探讨

合理设置刀具半径补偿值,灵活应用刀具半径补偿功能,对简化数控铣削编程有着非常重要的意义。文章分析常用的刀具半径补偿方式,以FANUCOi系统为例,探讨C刀具半径补偿。     

刀具半径补偿在CNC编程中能错误及正确应用

在CNC编程中,合理地引入刀具半径补偿,可以使刀具轮廓轨迹的处理变得更简单。但是,由于使用刀具半径补偿要遵循很多相应法则,因此造成一些编程员刻意避开使用刀具半径补偿。本文将从以下几个方面对刀具半径补偿在实际应用中出现的错误加以分析,并给出一些有益的建议,希望能够为读者提供解决此类问题的一些基本方法和思路。     

刀具补偿功能在数控加工中的应用

刀具补偿是数控加工中经常遇到的问题,该文首先从刀具补偿指令入手,就刀具半径补偿和刀具长度补偿在数控车削加工、数控铣削加工和加工中心加工中的应用进行了阐述。     

一种基于正交基神经网络算法的传感器误差补偿方法

为了提高传感器的误差补偿精度,提出了一种基于正交基神经网络算法的传感器误差补偿方法.研究了神经网络算法的收敛性,为学习率的选择提供了理论依据.为了验证算法的有效性,给出了传感器误差补偿实例.研究结果表明,基于正交基神经网络算法的传感器误差补偿方法具有高的误差补偿精度,因而是一种有效的误差补偿方法.     

五轴联动数控系统RTCP技术的研究与实现

为了实现高效的五轴加工,本文对五轴RTCP技术进行深入研究,通过对旋转角度的细分及插补点处非线性误差补偿,减小了加工中的非线性误差并满足补偿算法的实时性,通过对各轴速度进行约束的前瞻算法、减小了加工过程中的机床振动,从而提高了工件表面的加工质量.本文提出采用基于参数配置的运动学模型,提高了工件程序的可移植性.最后将该算法添加到GJ-310数控系统中,并进行了试验验证,结果表明该算法可以满足加工要求.     

基于LabVIEW数控机床几何误差补偿的研究方法

介绍一种由软件、硬件控制的数控机床几何误差补偿。误差补偿的原理主要是运用多体系统运动学理论建立机床几何误差模型,用硬件控制固化在程序存储器内的误差补偿程序完成补偿任务,并通过RS-232C实现数控机床与Windows平台通信与数据交换。     

Minimization of the kinematics error for five-axis machining

Kinematics of a particular five-axis milling machine can drastically change the machining accuracy. Therefore, the reduction of the kinematics error is an important problem associated with the tool path planning.Our new optimization method employs a closed form of the kinematics error represented as a function of the positions of the cutter contact points. The closed form is derived from the inverse kinematics associated with a particular five-axis machine and obtained through automatic symbolic calculations.The second component of the algorithm is the optimal setup of the part surface on the mounting table employed in an iterative loop with the generation of the cutter contact points.For a prescribed tolerance the proposed optimization allows for substantial reduction in the number of required cutter contact points. The reduction can be significant and may amount to long hours of machining if the machining time at the programmed feed is less than the sampling time of the controller.In turn, when the number of cutter location points is fixed, the error can be substantially reduced. However, this refers to commanded error wherein the dynamics of machine tool are not taken into account.We present an analysis, systematic numerical experiments and results of real cutting (ball nose and flat-end cutters) as an evidence of the efficiency and the accuracy increase produced by the proposed method. We also evaluate the relative contributions of the setup and the point optimization.The method is shown to work with advanced tool path generation techniques proposed earlier such as the adaptive space filling curves.The numerical and machining experiments demonstrate that the proposed procedure outperforms tool paths based on the equi-arclength principle and paths generated by MasterCam 9.     

Accuracy enhancement of multi-axis CNC machines through on-line neurocompensation

This research is devoted to one of the most fundamental problems in precision engineering: machine tool accuracy. The paper presents a new approach designed to improve the accuracy of multi-axis CNC machines through software compensation of geometric, thermal and dynamic errors. Based on a multi-sensor monitoring system, the proposed compensation scheme is built to ensure error prediction. Four steps are required to develop and implement this system: (i) measurement of individual error components along each axis using a laser interferometer system, (ii) sensor integration via an artificial neural network model for on-line error estimation, (iii) synthesis of the total error into a three-dimensional error form using a simplified kinematic model and finally (iv) error compensation. Implemented on a turning center, the neurocompensation approach has improved machine accuracy by reducing the maximum error without compensation from 70 m without compensation to less than 4 m.     

A study on automatic on-machine inspection system for 3D modeling and measurement of cutting tools

A 3D model of the maximum rotating envelope of a milling cutter with tool holder is required for Computer Aided Manufacturing (CAM) process design and machining simulation. The user may define the 3D model of the whole tool assembly in the tool library of CAM software. However, it is not convenient and reliable. Considering these problems, a new method based on single view 3D reconstruction algorithm has been proposed in previous research work, which is able to quickly reconstruct the 3D model of a cutter with tool holder while they are installed onto the spindle. As the extension of this work, this paper focuses on the recent progresses in order to improve the automation, accuracy, efficiency and reliability of tool modeling system. First, an improved flexible on-machine camera calibration procedure is proposed. The accurate motion of machine tool axis is used to calibrate the camera on machine tool instead of a physical calibration board. The whole procedure of calibration can be conducted automatically by running NC code. Therefore, the automation of vision system can be guaranteed. Second, the contour extraction module is improved by using a method of silhouette image composition. This method is applied to solve the problem of translucent and fuzzy cutter profile induced by motion blur. Third, the new algorithm for contour partitioning and classification are proposed, which is more reliable and robust. The reliability and accuracy of the vision system can be guaranteed. Finally, the vision system with an 8 mm lens and 1 mm extensions has been tested on different type of machine tool with smaller cutters. The average measurement accuracy is about 35 microns verified by comparison with a commercial tool setting system.     

基于四点偏置法的非可展直纹面侧铣刀位计算

针对非可展直纹面五轴侧铣加工的问题,分析了非可展直纹面几何特点,根据等距 映射下的极差不变性,提出了一种计算非可展直纹面叶片五轴侧铣刀位数据的新方法。以刀具包 络面与设计曲面之间的整体误差为优化目标,建立了圆柱铣刀侧铣非可展直纹面的刀位计算方 法,运用四点偏置法确定初始刀位,采用最小二乘法对初始刀位进行优化,建立刀轴矢量偏转模 型进一步修正刀位以减小过切误差。通过实例计算分析,表明该方法可以在一定程度上减小加工 误差。     

Tool selection for five-axis curvature matched machining

This paper presents an automatic cutting tool selection methodology for five-axis finish surface machining based on the techniques of curvature matched machining. The criterion for cutter selection is to minimize the machine errors and to maximize material removal rate using an optimal filleted end mill selected from a standard cutting tool library. Tool parameters investigated include cutter radius, cutter corner radius and cutter length. The maximum swept silhouette of the inclined tool is proposed and implemented as tool radii selection protocols for matching the change in surface curvature. Algorithms for detection and correction of local tool gouging and global tool interference are presented. The local distance between the cutter bottom and the surface is used to detect and correct local tool gouging. Global tool interference detection and correction is solved by studying the shortest distance between the part surface and the cutter body axis. A faceted approach is used to accelerate the distance calculations. The solution to the local and global gouging problems leads to the shortest, most rigid, tool in the library. These methods of automatic tool selection have been implemented in ROBLINE using the C-language on the system. ROBLINE is a precursor to CODE (Cimetrix Open Development Environment) which is a complete commercial off-line/on-line machine modeling, development and control package. Machined examples confirm the effectiveness of these methods.     

矢量法在刀具半径补偿技术中的应用研究

刀具半径补偿技术是CNC系统的关键技术之一,是加工轨迹插补运算的数据来源与依据。根据编程轨迹及刀具半径值规划出刀具中心的运动轨迹,尤其是轨迹转接点坐标值,是保证零件轮廓正确性的必要前提。引入方向矢量的概念,研究矢量法在刀具半径补偿技术中的应用,实现了C功能刀具半径补偿,很好地解决了二维刀补中唯一解的确定这一复杂难题。该算法已经应用于自主研发的TDNC-L4数控铣削系统和数控车削系统,初步实现了该理论成果的实例化验证。     

基于视觉定位的数控机床智能刀柄系统

针对航天领域某大型工件人工配打孔劳动成本高、制造效率低等问题,提出了一种基于视觉定位的智能刀柄系统,利用视觉算法对大型工件的多个安装孔进行自动识别和定位,并通过基准转换方法计算出安装孔在机床下的位置,将视觉补偿后的孔位位置发送给机床,即可实现机床对安装孔位置的自主感知和自动更新轨迹加工。将研究的系统和红外测头测量结果进行实验比对,结果表明,视觉定位平均误差0.05 mm,实际工件配合误差要求不超过0.3 mm,因此,研究的系统能满足实际生产需求。     

Comparing the kinematic efficiency of five-axis machine tool configurations through nonlinearity errors

Five-axis CNC machines represent a particular class of machine tools characterized by superior versatility. Little attempts were made in the past to compare directly their performances through a common indicator. In this sense, the present study proposes nonlinearity error as a valuable method to quantify the kinematic efficiency of a particular five-axis configuration. Nonlinearity error is defined as the maximum deviation of the cutter-location point from the reference plane generated by the initial and final orientations of the tool during linearly interpolated motions of the cutter along the intended tool path. The proposed concept has demonstrated that nonlinearity error occurs approximately around the middle of the linearly interpolated interval and therefore has validated the current post-processing practice of halfway cutter-location point insertion. The employment of nonlinearity error in the evaluation of the kinematic efficiency of vertical spindle-rotating five-axis machine tools revealed that for an identical machining task, configurations involving the vertical rotational axis tend to move more than those involving only horizontal rotational axes.