Investigation into micro abrasive intermittent jet machining

In the machining of small holes by the conventional micro abrasive jet machining, the colliding abrasives accumulate in the bottom of the hole, preventing the direct impact of successive abrasives onto the workpiece. As a result, the machining efficiency decreases as the machining progresses. This paper introduces a new method of micro abrasive jet machining, called micro abrasive intermittent jet machining (MAIJM), in which there exists a period of time during which no abrasive is injected into the gas stream from the nozzle so that the continuous flow of gas without abrasives from the nozzle could blow away any abrasives that have accumulated in the hole. Empirical models are developed for evaluation of the effect of MAIJM process parameters on the shape of the machined holes by proper design of experiments based on a Taguchi orthogonal array and by multi-variable linear regression. Further experiments are conducted to confirm the validity of the developed statistical model by comparing the model predictions with the experimental results.     

Automated supply of micro parts based on the micro slide conveying principle

Part supply is a major bottleneck for successful automation in micro assembly. So far, vibratory conveyors working according to the micro throw principle are applied predominantly. However, missing flexibility, fault liability and abrasive wear are significant disadvantages. In this paper, a multi body simulation model describing the micro slide principle including all major influencing parameters for micro parts is presented. By means of experiments with an especially designed piezoelectric conveyor, the functionality and advantages of this principle are demonstrated and the model is validated. Furthermore, optimization of the conveyor by automation, miniaturization and modularization is shown.     

磁场辅助微细磨料水射流加工系统的研制

通过研制磁场辅助微细磨料水射流加工系统以提高微细磨料水射流加工的稳定性,增强磨料水射流的能量,提高其加工能力。该加工系统主要由多轴运动装置、磁场发生装置、气液增压系统、微细磨料混合装置及其控制系统组成。微细磨料水射流的增压系统采用气液增压方式;磨料供给装置采用前混合式;利用Ansys软件优化设计磁场分布,以便获得喷嘴内均匀分布的磁场;其控制系统主要以PLC为核心控制元件,实现对喷嘴的运动、磁场、系统供压、磨料供给等的集成控制。通过设计人机交互控制界面实现磁场辅助微细磨料水射流加工系统的在线操作及控制。     

Tribological behavior of micro structured surfaces for micro forming tools

Mechanical micro machining processes, like milling and grinding are appropriate technologies for the flexible production of precise molds with complex shapes for metal forming processes. In most cases machining strategies are orientated towards form accuracy of the desired forming tool only. Thus, the generation of tribologically advantageous surfaces is often carried out in subsequent machining steps like honing. In micro scale the subsequent treatment of complex surfaces is very difficult. For that reason it is desirable to create the shape and a suitable surface texture with one tool in one step.This paper is focusing on the comparison of the tribological behavior of polished surfaces with structured surfaces machined by micro milling and micro grinding processes. Micro milling tools and grinding pins with ballend shape are used to create micro structured surfaces. The machining strategy (tool path and line pitch) was varied for both tool types in the same manner. The experiments were carried out on hardened cold working steel using tungsten carbide micro cutters with TiAlN coating and micro grinding pins with an abrasive diamond layer. White light interferometry was used to characterize the machined surfaces and determine the surface parameters. Moreover, a strip drawing test was set up to investigate the tribological behavior of the system consisting of the machined surfaces and thin sheet metals. The results of the strip drawing test suggest a relationship between micro structure and tribological behavior. Finally, the dependencies between machining technology, surface parameters and tribological behavior will be discussed.     

磨料流加工中夹具设计的研究

磨料流加工(AFM)是光整加工领域的一项新技术。磨料流加工由磨料流加工机床,夹具和流体磨料三部分组成。当用磨料流加工形状较复杂的零件时,夹具设计的好坏对表面加工质量和加工效率有重要的影响。本文分析了磨料通过工件孔道的特性。介绍了用于研究材料去除量与加工距离和形状关系的实验。材料去除量在通道两端比中间小是磨料流加工的一基本特性。本文讨论了如何避免因此而产生的工件变形以及如何利用这一特性来获取某种特殊效果。最后,给出了一个用于加工某不锈钢三通体的夹具。     

Micro Engineering

The paper addresses the questions of how micro products are designed and how they are manufactured. Definitions of micro products and micro engineering are discussed and the presentation is aimed at describing typical issues, possibilities and tools regarding design of micro products. The implications of the decisions in the design phase on the subsequent manufacturing processes are considered vital. Finally, manufacturing and assembly of micro products as well as the philosophy of micro factories are presented and discussed.     

分层厚度对微细电火花铣削加工模具及热压制品表面粗糙度的影响

分层厚度直接影响微细电火花铣削加工的加工效率及表面粗糙度。为了合理规划微细电火花铣削加工的分层厚度,提高加工效率,研究了分层厚度对微细电火花加工的模具型腔及相应热压成形制品表面粗糙度的影响,同时分析了热压成形制品表面与微模具型腔表面之间的关系,以及热压前、后微模具型腔表面轮廓的变化。结果表明:当电极轨迹重叠率一定时,模具型腔底面的表面粗糙度值随着分层厚度的增加而增大;分层厚度对型腔侧壁表面粗糙度无明显影响;热压制品表面轮廓算术平均偏差小于模具型腔表面轮廓算术平均偏差;热压后的模具表面轮廓发生了变化,表面粗糙度值Ra和峰高Rpk减小,峰谷Rvk增大。     

非牛顿流体微流场测量Micro PIV系统研究

介绍了一种专用于非牛顿流体微流动测量Micro-PIV系统,主要包括微流场激发、微流动观察记录与数据处理三大部分。针对非牛顿流体流动激发形式多样性的特点,微流场激发部分包括显微镜冷热台、波形发生器和磁场发生仪,可以产生激发非牛顿流体为流场所需的电、磁及温度场。观察记录部分主要包括荧光显微镜、CCD等,用于观察并记录荧光示踪粒子的运动,获取荧光示踪粒子运动的视频文件。数据处理部分用于将视频文件进行图像处理以得到所需流场数据。应用该系统对非牛顿流体5CB液晶在电场作用下所激发的微流动进行了测量,重点测量了液晶盒侧面的速度剖面图,所得到的试验结果与计算结果非常吻合,且比传统测量方法更加快速、准确。此外,对温度场变化产生的液晶缺陷进行了试验研究,得到了连续加热冷却状态下的液晶缺陷形成温度变化趋势,即形成缺陷的温度逐渐升高,从开始的31.25℃逐渐升高至34.4℃后保持平稳。     

High frequency bandwidth measurements of micro cutting forces

The miniaturization of machine components is perceived by many as a core requirement for the future technological development of a broad spectrum of products. One of the challenges in micro engineering is the development of economical micro systems that are flexible, functional and made of appropriate engineering materials. The mechanical removal of materials using miniature tools, known as a micro machining process, has unique advantages in creating 3D components using a variety of engineering materials, when compared with photolithographic processes. Since the diameter of miniature tools is very small, excessive forces and vibrations will significantly affect the overall part and tool quality. In order to improve the part and tool quality, accurate measurement of micro cutting forces is imperative. In this paper, we focus on the development of an ultra precision micro milling system and the measurement of micro cutting forces using a three-axis miniature force sensor and accelerometers. Since the inherent dynamics of the workpiece and overall machine tool affects the frequency bandwidth, we employ the Kalman filter approach to fuse the sensor signals and compensate for unwanted dynamics, in order to increase the bandwidth of the force measurement system. Based on accurate cutting force measurement, we can come up with the optimal process parameters to maintain desired tolerances and also monitor the process to prevent failures.     

磁性研磨加工方法的研究

介绍了磁性研磨的加工原理,不仅对磁极的形状加以分析,还对工件在磁场中的受力情况进行了理论分析。对淬硬后的工件外圆进行磁性研磨的加工试验,得出了不同的磁感应强度以及不同研磨时间对加工表面粗糙度和研磨量的影响;从而得出了优化的磁性研磨的加工参数。     

Finishing effects of spiral polishing method on micro lapping surface

This study presents a spiral polishing method and a device for micro-finishing purposes. This novel finishing process has wider application than traditional processes. This offers both automation and flexibility in final machining operations for deburring, polishing, and removing recast layers, thereby producing compressive residual stresses even in difficult to reach areas. Applying of this method can obtain a fine polished surface by removing tiny fragments via a micro lapping generated by transmission of an abrasive medium through a screw rod. The effect of the removal of the tiny fragments can be achieved due to the function of micro lapping. The method is not dependent on the size of the work-piece's application area in order to carry out the ultra precise process. The application of this research can be extended to various products of precision ball-bearing lead screw. The proposed method produces products with greater precision and more efficiently than traditional processes, in terms of processing precisions and the surface quality of products. These parameters used in achieving maximum material removal rate (MRR) and the lowest surface roughness (SR) are abrasive particle size, abrasive concentration, gap, revolution speed and machining time.     

单晶Cu材料纳米切削特性的分子动力学模拟

建立了单晶Cu纳米切削的三维分子动力学模型,研究了不同切削厚度下纳米切削过程中工件缺陷结构和应力分布的规律.纳米切削过程中,在刀具的前方和下方形成变形区并伴随缺陷的产生,缺陷以堆垛层错和部分位错为主.在纳米尺度下,工件存在很大的表面应力,随着切削的进行,工件变形区主要受压应力作用,已加工表面主要受拉应力作用.随着位错在晶体中产生、繁殖及相互作用,工件先后经过弹性变形——塑性变形——加工硬化——完全屈服4个变形阶段,随后进入新的循环变形.结果表明:工件应力-位移曲线呈周期性变化;切削厚度较小时,工件内部没有明显的层错产生,随着切削厚度的增大,工件表面和亚表层缺陷增加;切削厚度越大,对应应力分量值越小.     

Micro Electrochemical Machining of 3D Micro Structure Using Dilute Sulfuric Acid

Micro electrochemical machining (ECM) using ultra short pulses with tens of nanosecond duration is presented. 0.1 M sulfuric acid was used as electrolyte and 3D micro structures were machined on stainless steel. To prevent taper, a disk-type electrode was introduced. Using the disk-type electrode, taper could be eliminated. To improve productivity, multiple electrodes were applied and multiple structures were machined simultaneously. Since the wear of tool electrode is negligible in ECM, micro wire can be used as tool electrode. Using a platinum wire electrode with 10 urn diameter, various 3D features were machined on stainless steel plate.     

微铣刀制备技术与实验研究

微铣刀制备技术是微细铣削的关键技术之一,对微细铣削加工出的微小零部件的特征尺寸和表面质量有重要影响。从微铣刀具的材料与涂层及其制造工艺两方面,对微铣刀制备技术进行了介绍,并通过线电极电火花磨削方法制备了刀头直径为100μm的微铣刀,初步验证了基于自研μEM-200CDS2微细组合电加工机床开展微铣刀在位制备的能力。     

Trend-specific clustering for micro mass production of linked parts

In micro production, small tolerances, as well as size effects increase the requirement for a fast, precise, and reliable methodology that enhances the output of assemblies. In contrast to conventional approaches, a widening of the tolerance field enables an overall improvement of the output of a process chain while assuring functionality of parts. Therefore, the consideration of trends for building sections is essential for increasing the outcome by identifying sections that can be matched. This paper presents the Linked Parts Clustering Algorithm for the identification of trend-specific clusters in linked parts and demonstrates the area of application.     

Application of micro-EDM combined with high-frequency dither grinding to micro-hole machining

This research presents a novel process using micro electro-discharge machining (micro-EDM) combined with high-frequency dither grinding (HFDG) to improve the surface roughness of micro-holes. Micro-EDM is a well-established machining option for manufacturing geometrically complex small parts (diameter under 100 μm) of hard or super-tough materials. However, micro-EDM causes the recast layer formed on the machined surface to become covered with discharge craters and micro-cracks, resulting in poor surface quality. This affects the diameter of the micro-hole machined and undermines seriously the precision of the geometric shape. The proposed method that combines micro-EDM process with HFDG is applied to machining high-nickel alloy. As observed in SEM photographs and surface roughness measurement, HFDG method can reduce surface roughness from 2.12 to 0.85 μm Rmax with micro-cracks eliminated. Our results demonstrated that micro-holes fabricated by micro-EDM at peak current 500 mA followed by HFDG at 40 V can achieve precise shape and good surface quality after 6–8 min of lapping.     

Damage mechanisms during lapping and mechanical polishing CdZnTe wafers

CdZnTe wafers were machined by lapping and mechanical polishing processes, and their surface and subsurface damages were investigated.The surface damages are mainly induced by three-body abrasive wear and embedded abrasive wear during lapping process. A new damage type, which is induced by the indentation of embedded abrasives, is found in the subsurface. When a floss pad is used to replace the lapping plate during machining, the surface damage is mainly induced by two-body abrasive and three-body abrasive wear, and the effect of embed-ded abrasives on the surface is greatly weakened. Moreover, this new damage type nearly disappears on the subsurface.     

Machining of micro rotational parts by wire electrical discharge grinding

Micro rotational parts are used in several industrial sectors. Well-known applications are micro shafts of gears, ejector pins in forming tools, pin electrodes for micro electrical discharge drilling or micro stamping dies. Depending on the geometrical complexity of micro rotational parts different process variants of micro electrical discharge machining characterized by a rotating work piece can be used: wire electrical discharge grinding (WEDG) with fine wire electrodes, electrical discharge turning (EDT) with micro structured tool electrode, cylindrical electrical discharge grinding (CEDG) with micro profiled disk electrode. Characteristic to these process variants is the superimposed relative motion between the rotating electrodes and the feed. This relative motion can be varied in a wide circumferential velocity range to improve the material removal process. The paper gives an overview of kinematic and technological restrictions and requirements of the WEDG process influencing the process behavior with respect to the technological requirements of micromachining.     

Surface finish visualisation in high speed, ball nose milling applications

High speed milling systems are capable of producing complex parts that require little or no hand finishing operations. The machined surfaces are smooth to the touch and they are within the required machining tolerances. However, the visual surface appearance of the parts can be a quality issue because the surface patina is generated by a rotating, multi-flute, ball nose milling cutter as it moves over the surface of the part. Current CAM systems provide good simulating procedures to view the overall surface geometry with swept volume procedures, but they do not consider the micro pattern pertaining to the cutting action of individual cutter flutes. The work presented in this paper addresses this consideration and assesses two new methods to satisfy the need to account for, and predict, the surface machining effects from a ball nose milling cutter.     

摇摆式圆盘研磨机研磨轨迹型态的研究

研磨是使用研具和游离磨料进行微量加工的工艺方法，研磨运动轨迹是保证工件表面被均匀地切削，获得良好加工质量的决定性因素。本文介绍了摇摆式圆盘研磨机研磨轨迹模型和实验仿真情况，实验结果表明：当转速比越不规则或越接近除不尽时，研磨轨迹的分布越致密；且轨迹在加工面中心呈集中的趋势，使工件加工面中心处有凹陷的现象。