Robust tracking control for micro machine tools with load uncertainties

The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.

Modeling and Evaluating of Surface Roughness Prediction in Micro-grinding on Soda-lime Glass Considering Tool Characterization

The current research of micro-grinding mainly focuses on the optimal processing technology for different materials. However, the material removal mechanism in micro-grinding is the base of achieving high quality processing surface. Therefore, a novel method for predicting surface roughness in micro-grinding of hard brittle materials considering micro-grinding tool grains protrusion topography is proposed in this paper. The differences of material removal mechanism between convention grinding process and micro-grinding process are analyzed. Topography characterization has been done on micro-grinding tools which are fabricated by electroplating. Models of grain density generation and grain interval are built, and new predicting model of micro-grinding surface roughness is developed. In order to verify the precision and application effect of the surface roughness prediction model proposed, a micro-grinding orthogonally experiment on soda-lime glass is designed and conducted. A series of micro-machining surfaces which are 78 nm to 0.98 ~tm roughness of brittle material is achieved. It is found that experimental roughness results and the predicting roughness data have an evident coincidence, and the component variable of describing the size effects in predicting model is calculated to be 1.5x 107 by reverse method based on the experimental results. The proposed model builds a set of distribution to consider grains distribution densities in different protrusion heights. Finally, the characterization of micro-grinding tools which are used in the experiment has been done based on the distribution set. It is concluded that there is a significant coincidence between surface prediction data from the proposed model and measurements from experiment results. Therefore, the effectiveness of the model is demonstrated. This paper proposes a novel method for predicting surface roughness in micro-grinding of hard brittle materials considering micro-grinding tool grains protrusion topography, which would provide significant research theory and experimental reference of material removal mechanism in micro-grinding of soda-lime glass.

Theoretical and Experimental Research on Error Analysis and Optimization of Tool Path in Fabricating Aspheric Compound Eyes by Precision Micro Milling

Structure design and fabricating methods of three-dimensional （3D） artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial compound eyes. However, spherical optical compound eyes are less at optical performance than the eyes of insects, and it is difficult to further improve the imaging quality of compound eyes by means of micro-nano optical manufacturing. In this research, nonhomogeneous aspheric compound eyes （ACEs） are designed and fabricated. The nonhomogeneous aspheric structure is applied to calibrate the spherical aberration. Micro milling with advantages in processing three-dimensional micro structures is adopted to manufacture ACEs. In order to obtain ACEs with high imaging quality, the tool paths are optimized by analyzing the influence factors consisting of interpolation allowable error, scallop height and tool path pattern. In the experiments, two kinds of ACEs are manufactured by micro-milling with different too path patterns and cutting parameter on the miniature precision five-axis milling machine tool. The experimental results indicate that the ACEs of high surface quality can be achieved by circularly milling small micro-lens individually with changeable cutting depth. A prototype of the aspheric compound eye （ACE） with surface roughness （Ra） below 0.12 p.m is obtained with good imaging performance. This research ameliorates the imaging quality of 3D artificial compound eyes, and the proposed method of micro-milling can improve surface processing quality of compound eyes.

Advances in micro cutting tool design and fabrication

Microcutting is a precision technology that offers flexible fabrication of microfeatures or complex three-dimensional components with high machining accuracy and superior surface quality.This technology may offer great potential as well as advantageous process capabilities for the machining of hard-to-cut materials,such as tungsten carbide.The geometrical design and dimension of the tool cutting edge is a key factor that determines the size and form accuracy possible in the machined workpiece.Currently,the majority of commercial microtools are scaled-down versions of conventional macrotool designs.This approach does not impart optimal performance due to size effects and associated phenomena.Consequently,in-depth analysis and implementation of microcutting mechanics and fundamentals are required to enable successful industrial adaptation in microtool design and fabrication methods.This paper serves as a review of recent microtool designs,materials,and fabrication methods.Analysis of tool performance is discussed,and new approaches and techniques are examined.Of particular focus is tool wear suppression in the machining of hard materials and associated process parameters,including internal cooling and surface patterning techniques.The review concludes with suggestions for an integrated design and fabrication process chain which can aid industrial microtool manufacture.

Wear characteristics of Ⅴ shape diamond tool for micro prism pattern with Al alloys

The ultra-precision machining process using a single crystal diamond tool has been mainly used for machining molds of optical components.Since the micro patterns of various shapes having excellent surface roughness can be machined by using ultra-precision machine tools,the micro pattern on a large light guide plate (LGP) is mainly machined using a diamond tool.The tool wear occurs due to long machining distances and time while machining a large-area LGP mold.The deformation and dimensional error of micro pattern are caused by tool wear,as a result,the light efficiency of LGP declines.The characteristics of tool wear should be analyzed in order to precisely machine large-area LGP mold from all sorts of materials.The experiments were performed in order to compare wear characteristics of a V90° diamond tool using Al3003,5052,6061 and 7075.The prism pattern of depth 10 μm was machined in order to analyze characteristics of tool wear according to machining distances (0.5,1 and 1.5 km).The effects of tool wear on pattern shape were analyzed by applying overlapped cutting depths (Rough machining is (10+8+7) μm and Finish machining is (5+3+2+1) μm) by continuously machining a prism pattern of W shape of 25 μm in depth.

The Experimental Study of Micro-Tool Servo with Electrostrictive Actuator

An experimental study of micro-tool servo with electrostrictive actuator is presented.The design methods as well as the performance of the entire mechanism is given out.The results of the experiment show that the resolution of the micro-tool servo is 0.02μm and the frequency response is up to 200Hz,which satisfies the requirements of the ultra-precision machining.

Design and Manufacturing of Ultra-Hard Micro-Milling Tool

Based on the study of existing typical micro-milling tools and the actual demand for micro-milling tools, the P3 design principle and design flow for ultra-hard micro-milling tool were introduced to give basic guidance for the optimization of micro-milling tools. Then, according to the P3 design flow, the manufacturing process of polycrystalline diamond(PCD) micro-milling tool was proposed, and the PCD micro-milling tool with diameter of 0.5 mm was developed. Finally, the micro-milling test on the slot was carried out to study the milling performance of PCD micromilling tool.

Influence of tool deflection on micro channel pattern of 6:4 brass with rectangular tool

Machining experiment of micro channel structure with 6:4 brass was carried out by shaping process using a single crystal diamond tool. FEM simulation using solid cantilever beam model was analyzed. In result of experiment, tool deflection is observed as machining characteristics through result of experiments such as surface roughness, cutting force and burr formations. And the influence of tool deflection is experimentally proved.

基于GA-BP神经网络的微磨具磨损预测研究

为提高硬脆材料微结构的加工效率和精度,需要预测微磨具的不确定性磨损。基于微磨具在位视觉磨损检测和聚类分析,提出基于遗传算法的反向神经网络(genetic algorithm back propagation,GA-BP)模型。选取微磨具磨头截面面积损失量为指标,以表征微磨具不确定性磨损特征。利用K-均值聚类算法划分微磨具磨损状态阶段。最后构建以主轴转速、进给率、微槽深度、磨削长度和微磨具初始截面面积为输入层神经元,以磨头截面面积损失量预测值为输出层的GA-BP神经网络模型。设计不同工艺参数条件下的单晶硅微槽微细磨削实验,基于自搭建的机器视觉系统在位测量微磨具的磨头截面面积磨损量。将实验测得的微磨具磨损量作为训练数据,与传统高斯过程回归预测模型对比,验证GA-BP神经网络模型的有效性和准确性。结果表明,GA-BP神经网络模型能够实现不同工艺参数和不同磨削长度下的微磨具磨损预测,比传统高斯过程回归预测模型具有更高预测精度,平均误差精度达到5%,可以实现微磨具磨损阶段状态预测。

基于ABAQUS的微织构刀具切削钛合金仿真研究

构建无织构刀具和呈微凹坑、平行槽、垂直槽、斜向槽形貌的微织构刀具模型,并利用有限元分析软件ABAQUS研究了微织构刀具对钛合金车削过程的影响。通过分析不同形貌微织构刀具在切削过程中的切削力、摩擦系数、切削温度和工件表面残余应力,确定了较优的微织构形貌;研究了切削速度对微织构刀具切削钛合金性能的影响。结果表明,微织构刀具能有效降低切削力、摩擦系数和切削温度,使工件表面残余应力由拉应力转变为压应力,其中垂直槽微织构刀具能最有效地改善切削质量;随着切削速度的提高,切削力和切削温度增大,摩擦系数减小,工件表面残余应力由压应力向拉应力转变并有增大的趋势。

脉冲激光加工微细钻铣刀具研究现状及其发展趋势

微细钻铣刀具是微纳加工的重要工具,广泛应用于航空航天、3C电子产品、新能源汽车和医疗器械等高端装备关键零部件的微细加工。本文对比了多种微细钻铣刀具制造方法的优缺点发现,采用脉冲激光加工技术制造微细钻铣刀具具有良好的加工能力和适用范围;探讨了脉冲激光制造微细刀具的加工机理和加工工艺等的研究现状,提出了脉冲激光加工微细钻铣刀具的应用前景和发展趋势。

微纳织构涂层刀具切削性能研究进展

刀具磨损严重、服役寿命短仍然是切削加工所面临的难题。随着现代制造业的发展,钛合金、高温合金等难加工材料在工业中广泛运用。但由于这些材料具有低导热系数、变形系数小等特点,在机械加工中存在切削力和切削温度高、刀具磨损严重等问题,严重缩短了刀具的服役寿命。通过表面织构技术和表面涂层技术在刀具切削表面置入微纳织构和涂层可以显著改善切削性能;特别是在减小刀具磨损、降低切削力、切削温度以及刀-屑接触界面摩擦因数等方面具有显著效果。系统概述微纳织构涂层刀具的作用机理、切削性能以及应用领域,对微纳织构涂层刀具后续发展有重要推动意义。首先,介绍微纳织构涂层刀具的制备方式。其次,分析总结微纳织构涂层刀具的作用机理,并从抗磨损性、抗粘结性和刀具寿命三个方面总结微纳织构涂层刀具的自身性能。随后,从切削力、切削温度、刀-屑接触处的摩擦因数三个方面总结微纳织构涂层刀具的切削性能。最后对微纳织构涂层刀具在现代制造业中的应用进行阐述。提出在刀具切削表面同时置入微纳织构和涂层的当前研究现状以及未来发展方向,可为进一步研究微纳织构涂层刀具在切削加工中改善切削性能以及加工表面质量与性能提供参考。

“微时代”背景下研究生网络思政工作的典型经验与创新路径

习近平总书记在全国高校思政工作会议上明确指出:“要运用新媒体技术使工作活起来,推动思想政治工作传统优势同信息技术高度融合,增强时代感和吸引力。”网络思政教育旨在充分利用网络平台、新媒体等工具有针对性地对学生开展思想政治教育。研究生存在学业与生活双重压力,具有科研任务多、在校时间短与思政课程少的特点,亟须创新和优化研究生网络思政工作,丰富教育形式。“微时代”以“微工具”为传播媒介,以“小内容、大传播”为特点,强调教育双方实现平等、多元、快捷的“微交流”“微合作”。基于此,在“微时代”背景下,创新研究生网络思政工作,就要求转变教育模式、优化教育内容、创新沟通机制,以“微工具”“微交流”“微合作”实现“微教育”,进而提升研究生思政工作效能。

涂层刀具圆孔与直槽混合微织构激光制备工艺研究

针对刀具微织构激光制备质量欠佳的问题,文章研究了激光工艺参数对混合型织构表面形貌、几何尺寸和表面成分的影响规律。实验结果表明:对于涂层刀具表面圆孔和直槽混合微织构的制备,较为合理的激光参数为:加工次数N=6,扫描速度v=10 mm/s,激光功率P=20 W,激光频率f=120 kHz。涂层刀具织构底部和侧壁的结构以氧化物为主,在合理选择激光参数的情况下,刀具表面织构以外的涂层不会被破坏。通过涂层刀具混合微织构激光制备工艺的研究发现,织构宽度和深度的控制是制备微织构刀具的关键,所得规律为提高刀具织构加工质量提供参考依据。

复合材料的激光辅助切削加工研究

玻璃纤维增强复合材料(GFRP)与碳纤维增强复合材料(CFRP)在航空航天、汽车制造以及军事装备等领域有着广泛应用。考虑到传统铣削工艺与激光工艺在加工复合材料时均存在一定缺陷,利用激光—微细铣削工艺,针对热固性GFRP与CFRP材料,测量激光辅助微细铣削加工中GFRP与CFRP热影响区的形貌与尺寸,探究激光加工对不同区域基体的影响,分析加工过程与加工可行性。试验表明:GFRP与CFRP材料在激光加工中存在明显的、呈倒三角状的气化区与热影响区;在激光辅助微细铣削加工过程中,材料呈块状脱落,产生较少粉尘,均为脆性剥离;因热影响区的影响,在激光辅助微细铣削加工GFRP与CFRP时,刀具直径应大于热影响区宽度,以便在减少切屑粉末的同时降低刀具的磨损,从而降低材料的加工难度。

微铣削刀具磨损监测系统中麦克风阵列的消噪性能研究

在切削加工过程中,基于切削加工声音信号的刀具状态监测系统容易受背景噪声的干扰,为确保监测系统的稳定性,提出使用麦克风阵列和维纳滤波来干扰噪声的方法。在实验过程中,采用直径为700μm的微细铣刀对SK4高碳钢工件进行切削加工,并在切削过程提供人工噪声源,然后利用麦克风阵列获取切削时的声音信号。针对获取的声音信号,结合麦克风阵列与维纳滤波器进行滤波处理。结果表明,麦克风阵列结合维纳滤波能有效改善噪声对微刀具磨损监测系统的影响。此外,分析麦克风阵列排列方式对刀具磨损识别的性能影响,结果显示,环形阵列比直线阵列麦克风阵列系统能更有效地去除噪声,在一定频带宽度下选择适当的特征值,刀具磨损识别率可达到100%。

基于优化传递函数的机床微进给控制方法仿真

高强度运行环境下,数控机床往往要求较高的加工精度,为了提升机床微进给控制性能,提出一种基于优化传递函数的机床微进给控制方法。对机床微进给架构的驱动部分建模分析,获取驱动部分的传递函数与传动部分的传递函数,根据传递函数分析机床稳定性。将机床微进给全局滑模控制和内模控制有效结合,在高强度运行环境下建立一种全新的机床微进给控制器,通过新控制器实现高强度运行环境下机床微进给控制。仿真测试结果表明,所提方法可以有效降低机床运行能耗,提高工件加工效率,降低控制误差,说明上述方法可以取得预期控制效果。

Smart Cutting Tools and Smart Machining: Development Approaches, and Their Implementation and Application Perspectives

Smart machining has tremendous potential and is becoming one of new generation high value precision manufacturing technologies in line with the advance of Industry 4.0 concepts. This paper presents some innovative design concepts and, in particular, the development of four types of smart cutting tools, including a force-based smart cutting tool, a temperature-based internally-cooled cutting tool, a fast tool servo （FTS） and smart collets for ultra- precision and micro manufacturing purposes. Implemen- tation and application perspectives of these smart cutting tools are explored and discussed particularly for smart machining against a number of industrial application requirements. They are contamination-free machining, machining of tool-wear-prone Si-based infra-red devices and medical applications, high speed micro milling and micro drilling, etc. Furthermore, implementation tech- niques are presented focusing on： （a） plug-and-produce design principle and the associated smart control algo- rithms, （b） piezoelectric film and surface acoustic wave transducers to measure cutting forces in process, （c） critical cutting temperature control in real-time machining, （d） in- process calibration through machining trials, （e） FE-based design and analysis of smart cutting tools, and （f） applica- tion exemplars on adaptive smart machining.

Research on the Surface Micro-configuration in Vibration Cutting Particle Reinforced Metallic Matrix Composites SiC_p/Al

The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.