交叉杆型并联机床的虚拟装配和分析

采用PRO/E软件对BJ-04-02(A)型并联机床实物进行了建模和装配,并结合仿真分析软件ADAMS对模型进行动力学仿真,从而获取了并联机床的动力学曲线。     

交叉杆型并联机床的动力学性能研究

并联机床是一种20世纪90年代问世的新型数控加工装备,其机床刀具-夹具系统以及各杆的模态参数,对切削加工过程有着很大的影响.采用频响函数法,在BJ-04-02(A)交叉杆型并联机床上通过试验测定了Fraisa刀具和BT40C刀具夹头系统的模态参数以及6条腿的动态响应,为进一步加工零件和开展工艺研究奠定了必要的基础.     

高精度铣削中心

德国Kem Micro-und Feinwerk公司在汉诺威EMO2001展出了新开发的KERN MMP型加工中心(见图)。该机为高精密的铣削、钻削机床。机床定位精度为+1μm,重复精度为±1μm。精加工表面粗糙度可达Ra     

6-UPS并联机床误差分布特性

为确定6-UPS交叉杆式Stewart型并联机床BJ-04-02(A)的加工精度特性,运用逆向思维方式,从刀具平台发生给定位置误差、姿态误差时驱动杆长度的变化中获得机床精度信息。计算了工作空间内各位置点、各姿态下刀具平台发生给定位置误差、姿态误差时驱动杆长度的变化量;通过极值、倒数等运算,获得了单位杆长误差引起的刀具平台位置、姿态误差的上下限,并给出了位姿误差在工作空间内的分布特性。     

改善线切割加工表面粗糙度的措施

表面粗糙度是电火花线切割机床国家标准(GB7926-87)中工件精度第三项检验项目。其要求是:对12mm×12mm×40mm标准样块按走向为45°线切割成斜方,材料去除率大于20mm~2/min时,表面粗糙度R_α≤2.5μm,表面粗糙度值问题一直是电火花线切割加工工艺中严重的问题之一。笔者在可调线架DK7725D型线切割加工机床上进行了大量的加工试验,发现加工表面粗糙度超值的主要原     

介观尺度微型铣床开发及性能试验

针对微机电系统(Microeletro mechanical system, MEMS)技术和超精密加工技术局限,开展面向介观尺度微细铣削技术的研究。首先根据介观尺度铣削的加工特点,对其机理研究的关键问题进行详细的分析和讨论,提出微细铣削理论的研究重点及研究方法。然后在分析微细铣削成形条件和加工要求的基础上,开发微型铣床系统,并对系统各组成子系统及性能指标进行描述。最后开展机床加工性能评估试验,通过精度测量、误差分析和误差补偿提高工作台的定位精度达到1.62 μm,采用直径0.127 mm铣刀开展微铣削试验,通过表面粗糙度测量和同心圆切削试验评估机床的加工精度,在此基础上通过复杂零件加工实例进一步说明机床的加工能力,论证小型化机床加工技术的可行性和实用性。     

弯管内表面数控铣削加工方法研究

介绍了依据五轴联动加工原理避免弯管内表面加工干涉和改善切削不均匀的加工方法,进行了实验工艺规划、加工区域划分、数控程序编制等研究。采用球头刀具,调整刀具姿态,使刀具和工件表面的位置角近似不变,在四轴及五轴联动机床上进行了样件的试制。研究结果表明,该铣削加工方法可避免刀具与工件的局部干涉和整体干涉;切削状态稳定;最终表面质量一致性好,粗糙度满足技术要求（Ra=3.2μm）。研究结果为核电主管道以及同类弯管内表面的铣削加工提供了理论和试验依据。     

镍基高温合金工件异形孔加工工艺的研究

根据航空发动机涡轮盘上异形孔结构复杂及镍基高温合金材料难加工的特点 ,采用钻削、铣削与磨削工艺的不同组合、选用新型涂层刀具和相应的切削参数进行了工艺试验。通过分析试验过程中刀具、砂轮的磨损(破损 )情况及其对异形孔加工精度和表面粗糙度的影响 ,探讨了铣削、磨削加工镍基高温合金涡轮盘异形孔的可行性。研究结果表明 ,通过优化加工参数 ,涡轮盘异形孔钻削 铣削工艺可有效替代常用的电火花加工工艺。     

大力发展拉床、组合机床以满足用户的需要

一、拉床 拉床是一种高效率的金属切削机床,用于加工各种几何形状的内孔及外表面。最近,还发展了一种仿形拉削,可加工空间曲面。只要生产批量足够大,几乎大多数铣削工序用拉削工艺替代都是经济的。 拉削精度一般在7～9级,其一般表面粗糙度为 Ra 1.6～6.3 μm,个别为 Ra 0.32～0     

钛合金拉伸高速铣削试验研究

通过对钛合金TC4在拉伸状态下的铣削试验,重点研究了高速铣削对钛合金TC4(Ti6A14V)表面残余应力和表面粗糙度的影响,得到了在不同切削参数下钛合金TC4表面残余应力和表面粗糙度的实验数据.实验结果表明,拉伸装夹基本不影响表面粗糙度,但可以大大提高加工表面残余压应力并增大残余压应力层的厚度,为开展钛合金拉伸高速铣削加工提供了依据.     

异形滚柱的在线电解修型成型磨削工艺试验研究

介绍了一种用于汽车和摩托车上先进超越离合器异形滚柱的在线电解成型(ELID)磨削加工工艺试验及相关设备与装置,主要包括成型磨削的工艺实施方案,在平面磨床上实现成型磨削的工装设计及在线电解砂轮修型的装置设计与布局等问题。理论上分析了ELID成型磨削在加工中能按照理想的成型曲线自动修正砂轮母线的形状,从而达到很高的形状精度和较低的表面粗糙度。总结了影响加工质量和效率的因素和规律;同原来的成型拉削相比,采用成型磨削具有效率、质量与稳定性、工具成本和管理等方面的诸多优势。     

Improved Stiffness Modeling for An Exechon-Like Parallel Kinematic Machine(PKM) and Its Application

Hole drilling or contour milling for the large and complex workpieces such as automobile panels and aircraft fuselages makes a high combined demand on machining accuracy, stiffness and workspace of machining equipment. Therefore, a 5-DOF(degrees of freedom) parallel kinematic machine(PKM) with redundant constraints is proposed. Based on the kinematics analysis of the parallel mechanism using intermediate variables, the kinematics problems of the PKM are solved through equivalent kinematics model. The structural stiffness matrix method is adopted to model the stiffness of the parallel mechanism of the PKM, where the stiffness of each joint and branch component is obtained by stiffness formula and finite element analysis. And the stiffness model of the parallel mechanism is improved by correction coefficient matrix, each element of which is constructed as a polynomial function of three independent end variables of the parallel mechanism. The terminal stiffness matrices obtained by simulation result are used to determine the coefficients of polynomial function by least square fitting to describe the correction coefficient over the workspace of the parallel mechanism quantitatively. The experiment results prove that the modification method can greatly improve the stiffness model of the parallel mechanism. To enhance the machining accuracy of the PKM, the proposed kinematics model and the improved stiffness model are utilized to optimize the working stiffness of parallel machine by searching the best relative position of parallel machine and workpiece. A plate workpiece taken as example is examined in the case study section, which demonstrates the effectiveness of optimization method.     

并联机床加工船用螺旋桨及CAM技术研究

主要研究用并联机床加工整体式船用螺旋桨的技术以及用CAD／CAM系统进行螺旋桨辅助加工的方法。研究了并联机床加工螺旋桨的工艺方案，提出了加工螺旋桨的并串联多轴数控加工系统，分析了螺旋桨数控加工的工艺过程；介绍了在UG／CAM环境下进行螺旋桨加工的刀具轨迹编程和用Vericut加工仿真系统进行加工仿真的方法和过程；并进行加工实验。用于加工螺旋桨的并联机床具有结构简单，造价低和占地面积小等优点，具有广泛的应用价值和发展前景。     

用七轴联动并串联机床加工汽轮机叶片

1.概述 图1为六轴联动的并联机床示意图,它是由六根驱动杆并行地连接在固定平台和活动平台之间,由驱动杆长度的变化来实现固定在动平台上的刀具位姿的改变,以进行加工。它具有六个自由度,可用于加工具有复杂曲面的零件,如叶片、叶轮和复杂模具等。     

混气电解加工探讨

电解加工是利用金属在电解液中发生阳极溶解反应而去除工件上多余的材料、将零件加工成形的一种方法。电解加工的加工精度不仅与加工间隙有关,还与机床、工艺装备、工具阴极、工件、工艺参数等诸多因素有关,通常采用混气电解加工、脉冲电解加工、小间隙电解加工和改进电解液等措施提高加工精度。其中混气电解加工是将具有一定压力的气体与电解液按一定比例混合在一起,然后将这种混合物加入到工件的加工间隙中去进行电解加工的一种方法。混气电解加工可以缩小加工间隙,提高电解加工的加工精度和复制精度,但混气电解加工的微观不平度和不直度还不理想。从气液混合比、混气电解加工的特性以及混气电解加工的工艺三个方面对混气电解加工的原理进行一定的探讨,希望摸索一种提高电解加工精度的方法。     

用七轴并联机床加工叶片及后置处理技术

根据六轴并联机床加工汽轮机叶片存在的问题，提出在机床工作台上串联一个数控转台，实现七轴联动，以提高叶片加工的质量和效率，并提出了用七轴并联机床加工叶片的加工方案和加工工艺；提出了利用Uni-graphics(UG)进行叶片的辅助加工，包括生成叶片的三维造型、进行刀具轨迹编程和加工仿真；提出了在UG/POST的基础上开发面向并联机床的后置处理器的方法，以及七轴并联机床加工的后置处理算法。     

Investigations of the electrodischarge machining process for various electrode kinematics

In electrodischarge machining, the material excess is removed as a result of complex mass, heat and electric charge transport processes, which have a random and often unstable character. Investigations on classical electrodischarge sinking have shown that within steady-state process parameters, the standard deviation of the workpiece dimensions (a measure of accuracy) decreases with the decrease of the machined area. It is possible to take advantage of this fact by using an electrode with a working area smaller than the machined area and different electrode kinematics than in classical sinking. This assumption was corroborated by investigations on electro discharge sinking machine by means of a flat and a segmental rotating electrode as well as by means an electrode moving above the machined surface.     

Prediction and compensation of machining geometric errors of five-axis machining centers with kinematic errors

Kinematic errors due to geometric inaccuracies in five-axis machining centers cause deviations in tool positions and orientation from commanded values, which consequently affect geometric accuracy of the machined surface. As is well known in the machine tool industry, machining of a cone frustum as specified in NAS979 standard is a widely accepted final performance test for five-axis machining centers. A critical issue with this machining test is, however, that the influence of the machine's error sources on the geometric accuracy of the machined cone frustum is not fully understood by machine tool builders and thus it is difficult to find causes of machining errors. To address this issue, this paper presents a simulator of machining geometric errors in five-axis machining by considering the effect of kinematic errors on the three-dimensional interference of the tool and the workpiece. Kinematic errors of a five-axis machining center with tilting rotary table type are first identified by a DBB method. Using an error model of the machining center with identified kinematic errors and considering location and geometry of the workpiece, machining geometric error with respect to the nominal geometry of the workpiece is predicted and evaluated. In an aim to improve geometric accuracy of the machined surface, an error compensation for tool position and orientation is also presented. Finally, as an example, the machining of a cone frustum by using a straight end mill, as described in the standard NAS979, is considered in case studies to experimentally verify the prediction and the compensation of machining geometric errors in five-axis machining.     

高温合金薄壁盘复杂零件加工变形控制方法

薄壁盘由于材料刚性较差等原因难以确保零件加工精度，容易引起变形，对此，提出了高温合金薄壁盘复杂零件加工变形控制方法。分析零件加工过程中产生的变形因素，包括夹装方式、刀具性能参数、工件自身因素、机床定位精度不够以及温度控制不佳等；确立所有工序历史误差源集合，生成误差传递矩阵，构建变形误差源诊断模型；针对不同误差源，提出针对性控制方法，通过最小二乘多项式拟合算法计算让刀误差，并对其补偿；通过有限元分析法建立工件几何模型，设立刚度控制函数，弥补工件自身缺陷；针对机床定位精度和温度分别设计控制函数，实现零件加工变形的综合控制。实验结果表明，所提方法明显减少了零件加工变形现象，保证了切削力平稳，提高了零件质量。     

Generating complicated surface with electrolyte jet machining

In the electrolyte jet machining (EJM), the electrolytic current is supplied between the anodic workpiece and the cathodic nozzle via the electrolyte which is ejected from the minute nozzle. Only the workpiece material exposed to the jet is removed due to the anodic dissolution, because the electrolytic current is restricted to the limited area by the jet. In this study, an electrolyte jet machining system which can be used to process the complicated three-dimensional surface was constructed. This system is composed of an XY stage, a rotating axis and a high-speed bipolar power supply, all of which are cooperatively controlled by a personal computer. An algorithm was developed to obtain the scanning path and speed of the nozzle to process complicated shape by superimposing simple patterns. The optimized path and speed were thus obtained so that the summation of the squared difference between the superimposed and the required patterns at every checking point becomes minimal. In order to verify the effectiveness of the developed algorithm, simulation and experiment were carried out and the machining accuracy was analyzed. The good agreement between the simulated and produced shapes with the required one proves that the algorithm meets the purpose properly. Besides, the effect of machining conditions, especially the current density on surface roughness of produced patterns was examined. It was clarified that a high current density is not only necessary to reduce machining time but also to improve the surface roughness.