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.     

新型的复杂曲面磁粒光整加工机床

介绍了一种复杂曲面光整加工机械--三坐标数字化磁粒光整加工机床.该机床通过对复杂曲面的数字化测量和自动编程,得到磁极与工件保持一定间隙沿工件表面运行的加工轨迹,利用吸附在工具磁极上面的磁性磨料为工具,通过磁极带动磁粒沿工件表面作高速旋转,从而实施对工件表面的光整加工.该机床的研制成功实现了复杂曲面光整加工的自动化.     

含雕塑曲面和岛的模具型腔粗加工刀具组合优化方法

模具型腔粗加工正在从传统的单刀策略向多刀组合策略转变,粗加工刀具组合优化可显著提高模具整体加工效率。现行的CAM编程软件刀具的选择主要基于编程者的经验,易于出错且很难做到最优化。研究提出了模具型腔粗加工中基于CAD实体模型自动进行刀具选择和优化的系统化方法,建立了优化数学模型,设计了相应的算法,包括截交轮廓的生成、内外环的判断以及搜索层的合并。所提方法和算法在UG二次开发环境下进行了编程实现和算例验证,结果表明该方法是可行有效的。     

机床进给系统摩擦特性分析及改善措施研究

在建立机床进给系统动力学模型的基础上,分析了不同的摩擦特性下引起系统振荡的主要原因,为了解决超精密进给中的振荡问题,提出二级进给策略提高系统的综合刚度和采用导轨软带改善摩擦因素与速度的关系。最后通过试验证实：应用所提出的改善措施,在5 000 N载荷下进给的控制精度达到10 nm。     

IN-PROCESS TOOL CONDITION MONITORING USING ACOUSTIC EMISSION SENSOR IN MICROENDMILLING

Recently researchers and manufacturers have shown keen interest in fabricating micro-components through tool based mechanical micromachining processes namely micromilling, microdrilling, microturning, etc. In this scenario, microendmilling is used in the manufacture of micro-molds, micro-dies, micro-channel, micro-gear, etc. The major issue in microendmilling process is the unpredictable life of the micro-tool and its premature failure during operations. Therefore in this work, an attempt has been made to monitor the tool condition (in-process) using acoustic emission (AE) sensor in microendmilling of different materials such as aluminum, copper and steel alloys. From this study, it is observed that there is a strong relationship between the tool wear (flank wear) and acoustic emission (AE_RMS) signals, surface roughness (R_a) as well as chip morphology. In order to understand the mechanism of tool wear, SEM and EDAX analyses were carried out on the microendmill after machining. Scanning Electron Microscope (SEM) and energy dispersive X-ray spectroscopy (EDAX) analyses indicated occurrence of the tool wear mechanism such as adhesion and plastic deformation in all three materials. Coating delamination is also observed while machining steel alloy. This work provides significant and new knowledge on the usage of AE sensor in monitoring the tool condition and understanding the tool wear mechanism in microendmilling of different materials.     

A GEOMETRICAL APPROACH FOR REDUCTION OF TOOL SHAPE DEGENERATION IN ELECTRIC DISCHARGE MACHINING (EDM)

In this study, the geometric wear characteristics of tool electrodes were obtained for various pulse time, discharge current and machining depth settings in electric discharge machining. Different forms of protrusions were machined on the front surface of the tool to reduce the geometric wear. Significant reductions in original tool geometric wear characteristics (front wear, side wear and edge wear) were obtained with the use of square cross-section protrusions. The dimensions of the square cross-section protrusions were modeled mathematically in terms of machining parameters used in the experiments.     

SURFACE FINISH AND TOOL WEAR CHARACTERIZATION IN HARD TURNING USING A MATHEMATICAL CUTTING TOOL REPRESENTATION

The development of a general 3D model for a corner-radiused, chamfered, edge-honed cutting worn tool is elaborated. The surface of the cutting tool was constructed using one angular scalar specifying location on the corner radius and leading/trailing edges and another non-dimensional scalar for specifying location on the relief, edge-hone, chamfer and tool-top. Then, for given geometric parameters and cutting conditions, the angular extremities of contact on the corner radius and leading/trailing edges was obtained and validated. The kinematic surface finish on the workpiece surface including the Brammertz and sideflow effects was then simulated in typical hard turning. The model was expanded to allow wiper edges and flank wear. A simplified crater wear model was adopted for continuous hard turning to allow virtual cross-sectioning. Accurate estimation of flank and crater wear volume was also enabled. The model results for the fresh tool agreed with well-known trends from 2D modeling. Preliminary results indicate that there exists a geometric basis for higher R_a and R_t for a worn tool. The Brammertz effect simulation, though not in agreement with the data of Knuefermann (2003 Knuefermann , M.M.W. ( 2003 ) Machining surfaces of optical quality by hard turning, School of Applied Sciences, Cranfield University, Cranfield, Bedfordshire, UK . [Google Scholar]) corroborated the modification proposed therein.     

自适应交互PID在液压伺服系统中的应用

自适应交互算法实现简单,能够在未知系统模型的前提下完成控制参数梯度递减,使系统控制性能趋向优化。将自适应交互算法引入到传统的PID控制器中,构成一种自适应交互PID控制器,将该控制器应用到宝钢2050粗轧液压立辊压下系统中,结果表明在外界扰动和系统工况发生变化时,该控制器能够自适应调节控制器参数,使控制系统取得满意的控制效果。     

数控机床位置控制系统仿真

本文介绍了数控机床交流伺服位置控制系统的结构及其简化模型,并采用实验测试与SIMULINK仿真相结合的方法,方便地确定了模型参数。通过对某型位置控制系统的实际测试与仿真,验证了该方法确定参数的有效性以及位置控制系统简化模型的实用性。     

应用“力信号时间序列分析”在线监测铣削过程中刀具破损

一般铣削加工中用于刀具破损监控的力信号时间序列建模方法已为很多科研工作者探讨和研究,并取得了很多成果。本文通过对铣削机理的分析,决定将力信号中确定性的部分分离掉,而采用一阶自适应自回归时间序列和简单的二阶差分方法跟踪信号中的剩余部分（随机部分）。在铣削过程中出现的铣削瞬态（铣削中的切入、切出、凹孔、槽沟和工件几何缺陷等现象）,将不会影响这种方法对刀具破损现象的识别。实验室的研究结果表明这种方法具有很高的实用性。     

软体磨具新技术

零件曲表面的磨光,抛光技术是精密加工技术领域的难题,传统的磨具难以直接对不规则的曲面进行加工。作者研究的软磨具,是一种体内均匀含磨料的新型高分子复合材料、磨料和抛光粉为加工要素,聚氨酯基网链状高分子材料为连接剂并为抛光要素。新型软磨具为三维柔软的弹性体,能适应任意曲率的零件（金属或非金属）表面的磨光和抛光要求。本文包括新型软磨具的生成理论,制造技术和曲面零件抛光的工艺性能试验研究。     

慢刀伺服车削刀具半径定向补偿的分段逼近求解

复杂曲面的慢刀伺服车削加工过程中,采用刀具法向补偿算法会在各个直线轴产生补偿量,加工法向矢量突变的曲面时,这种算法并非最优,将补偿量只应用于负载较低的直线轴却是更优的选择。提出一种基于线段逼近的刀具半径定向补偿数值求解算法来求解定向刀位点,通过半径细分的策略使法向误差收敛。算法实例验证及与相关算法的对比结果显示,该算法适用于点云构成的曲面或分段曲面的刀具半径补偿。     

超精密快刀伺服加工复杂光学面形的技术研究

超精密快刀伺服加工技术适用于复杂面形光学零件的高效优质加工。文中通过分析快刀伺服加工的控制结构、压电陶瓷驱动性能,进行了超精密快刀伺服装置的设计与研制,建立了其传递函数模型。最后完成了典型复杂面形光学零件的加工试验,并对加工结果进行测试与分析,测试结果表明满足了设计的性能指标要求。     

曲面5轴加工中全局干涉检查与刀位修正

提出了一种求解曲面到刀具极值距离的方法,以解决曲面5轴数控加工中刀具与曲面的干涉问题。将曲面上的点投影到刀轴上,求出曲面到刀轴的最小距离,直接计算出刀具与曲面的干涉量,并对干涉刀位进行了修正,成功地解决了曲面与刀具的全局干涉问题。实际应用表明,该方法效率高、精度高。     

MOTION ERROR ESTIMATION OF 5-AXIS MACHINING CENTER USING DBB METHOD

In order to estimate the motion errors of 5-axis machine center, the double ball bar (DBB) method is adopted to realize the diagnosis procedure. The motion error sources of rotary axes in 5-axis machining center comprise of the alignment error of rotary axes and the angular error due to various factors, e.g. the inclination of rotary axes. From sensitive viewpoints, each motion error is possible to have a particular sensitive direction in which deviation of DBB error trace arises from only some specific error sources. The model of the DBB error trace is established according to the spatial geometry theory. Accordingly, the sensitive direction of each motion error source is made clear through numerical simulation, which is used as the reference patterns for rotational error estimation. The estimation method is proposed to easily estimate the motion error sources of rotary axes in quantitative manner. To verify the proposed DBB method for rotational error estimation, the experimental tests are carried out on a 5-axis machining center M-400 (MORISEIKI). The effect of the mismatch of the DBB is also studied to guarantee the estimation accuracy. From the experimental data, it is noted that the proposed estimation method for 5-axis machining center is feasible and effective.     

INDUCTION-HEATED TOOL MACHINING OF ELASTOMERS—PART 2: CHIP MORPHOLOGY, CUTTING FORCES, AND MACHINED SURFACES

The induction-heated tool and cryogenically cooled workpiece are investigated for end milling of elastomers to generate desirable shape and surface roughness. Elastomer end milling experiments are conducted to study effects of the cutting speed, tool heating, and workpiece cooling on the chip formation, cutting forces, groove width, and surface roughness. At high cutting speed, smoke is generated and becomes an environmental hazard. At low cutting speeds, induction heated tool, if properly utilized, has demonstrated to be beneficial for the precision machining of elastomer with better surface roughness and dimensional control. Frequency analysis of cutting forces shows that the soft elastomer workpiece has low frequency vibration, which can be correlated to the surface machining marks. The width of end-milled grooves is only 68 to 78% of the tool diameter. The correlation between the machined groove width and cutting force reveals the importance of the workpiece compliance to precision machining of elastomer. This study also explores the use of both contact profilometer and non-contact confocal microscope to measure the roughness of machined elastomer surfaces. The comparison of measurement results shows the advantages and limitations of both measurement methods.     

EDM石墨电极快速研磨成型研具的开发研究

简介Hauseman研磨研具的特点、制造要求和制造方法;对研具配方进行深入的理论分析,在此基础上,通过实验获得研具制造的最佳配方,并进行了研磨实验给予验证。     

具有状态观测器的广义动态矩阵控制在板带轧机位置伺服系统中的应用

板带轧机的构成是复杂的,其控制系统日益精密化和智能化,但是目前广泛应用于现场的比例积分微分(PID)控制策略,由于鲁棒性较差,难以满足进一步提高板带轧机控制精度的要求。针对板带轧机位置伺服系统,应用广义动态矩阵控制理论,设计预测控制器,并采用滚动优化、反馈校正的控制策略。构造状态观测器,使控制系统具有带观测器的状态反馈形式,不断地修正预测模型,增强了系统的鲁棒性。所研究控制算法基于系统的阶跃响应,具有较强的稳定性和鲁棒性。提出上述控制策略的计算机控制实现方法,仿真研究结果表明该方法远比目前带钢生产中广为采用的PID控制策略优越,具有智能性且易于实现。     

光学自由曲面快速刀具伺服车削误差的补偿

受各种误差因素以及周期性变化的切削力的影响,快速刀具伺服金刚石车削技术往往难以用一次车削获得满足光学性能要求的自由曲面。本文提出了一种利用线性差动传感器(LVDT)实现高精度接触式自由曲面在位测量的方法。该方法结合两自由度快速刀具伺服系统,实现了基于快速刀具伺服(FTS)的自由曲面车削加工的误差补偿。试验结果表明,该技术将自由曲面的加工精度提高了20%,表面粗糙度降低18.1%,解决了FTS系统与机床运动的同步问题,可补偿机床xyz三向运动误差,可用于自由曲面加工误差的修正。该方法还可用于不对称幅度较大的曲面或硬脆性材料的加工等,故促进了高精度光学自由曲面的推广应用。     

复杂光学表面的快刀伺服加工特性与路径规划

复杂面形和微结构阵列等类型的光学元件应用范围越来越广,传统的机械加工方法难以满足面形精度和加工效率要求,超精密快刀伺服(Fast tool servo,FTS)是实现这类零件优质高效加工的有效手段.但是在复杂光学表面的快刀伺服加工中,面形的高低起伏将会使刀具和工件的相对位置实时变化,导致加工状态恶化、面形精度下降,甚至...