硅镜超声加工声学系统设计

近年来,超声加工方法已经越来越多地应用于脆硬材料的加工,超声声学系统是功率超声设备的核心和关键所在,其设计的好坏直接影响到其应用的效果.在分析超声声学系统工作原理的基础上,给出了该声学系统的具体设计方案,并且专门针对硅镜超声加工声学系统进行了设计及实验.实验结果表明,所设计的声学系统性能比较稳定,换能器发热较少,效率较高.     

机器人精加工陶瓷原型技术的路径规划研究

研究了机器人精加工陶瓷原型技术的路径规划方法.生成四种加工路径方案,对比分析了采用这些加工路径得到的精度和效率,提出一种合理的机器人精加工陶瓷原型路径设计方案.根据此方案生成加工路径,实际加工了用于熔射制模的陶瓷原型,其精度及表面质量均满足熔射要求,验证了该加工路径方案的可行性.     

直壁筒形件多道次增量成形工艺研究

通过对筒形件数控增量成形工艺的分析和研究,提出了以壁厚均匀化、提高成形极限为目的的直壁件多道次成形路径规划方案.设计了加工轨迹,通过实验研究,对成形路径,尤其是第一道次进行了优化,在此基础上加工获得了高径比为0.5的直壁筒形工件.     

钛合金椎间融合器加工关键技术研究

因钛合金材料具有无毒、无磁性和良好的生物相容性,在医疗器械等行业得到广泛应用.针对钛合金材料的特点和加工特性,以椎间融合器为研究对象,制定加工方案,设计工装夹具.利用SolidWorks Simulation有限元分析软件,对采用不同走刀路径切削时零件的应力、位移和应变进行分析比较,确定合理的走刀路径,为加工满足精度要...     

硅镜轻量化结构优化与实现

为了保证在高的面形精度的前提下尽可能地降低硅镜的质量,通过对多种轻量化结构的分析与对比,确定了具体轻量化结构形式并对其进行了优化设计。通过计算机仿真分析证明了该优化设计方案的可行性,并采用超声加工方法实现了硅镜轻量化加工。试验结果表明：轻量化加工的硅镜镜体质量明显降低;虽然镜面精度有所降低,但仍能满足光学系统的设计要求。     

考虑去除深度的砂带磨削路径规划方法

目前多数研究将加工轨迹规划作为单纯的几何问题,没有考虑力学影响,难以满足高精度加工要求。为了提高砂带磨削的加工精度,以其路径规划为研究对象,提出了一种基于去除深度的路径规划方法。基于赫兹接触理论,建立了砂带与工件接触区域的压强分布模型。基于Preston方程推导了材料线性长度去除深度方程,并最终建立了材料去除深度模型。以去除深度模型为基础,以残留高度为约束,建立了砂带磨削加工间距的规划方法,并给出了加工坐标的计算公式。实验结果表明,该路径规划方法可以避免过加工与欠加工现象,有效降低工件表面的残留高度,提高产品加工质量。     

硅晶片抛光加工工艺的试验研究

双面抛光已成为硅晶片的主要后续加工方法,但由于需要严格的加工条件,很难获得理想的超光滑表面.本文设计了新的硅片双面抛光加工工艺路线,并在新研制的双面抛光机上对硅晶片进行抛光加工,通过试验,研究了不同加工参数对硅晶片表面粗糙度和材料去除率的影响.采用扫描探针显微镜和激光数字波面干涉仪分别对加工后的硅晶片进行测量,试验结果表明:在优化试验条件下硅晶片可以获得表面粗糙度0.533 nm的超光滑表面.     

工程陶瓷孔复频超声加工方法的研究

超声加工方法广泛应用于工程陶瓷等硬脆材料的加工生产中。传统超声加工方法运动部件较多,操作复杂,为提高加工效率、降低成本,提出了复频超声加工方法,并建立了自由质量块的数学模型,分析了复频超声加工方法的加工原理,设计并加工了一套复频超声加工装置,并对陶瓷材料进行了实验研究,得到不同加工条件下各试件的材料去除率;比较各试件的材料去除率,发现复频超声加工方法相较于传统超声加工,其加工效率可以提高3倍,这为复频超声加工的设计及推广提供了理论指导。     

多边体超声切边技术

本文讨论了硬脆材料超声加工的机理,设计了多边体超声切边机和工具方位调整系统,研究了多边体超声切边声学系统,进行了多边体超声加工试验。结果表明,超声加工可以有效地对硬脆材料进行多边体加工。     

硅晶片抛光加工工艺的实验研究

双面抛光已成为硅晶片的主要后续加方法,但由于需要严格的加工条件,很难获得理想的超光滑表面.设计了硅片双面抛光加工工艺新路线,并在新研制的双面抛光机上对硅晶片进行抛光加工,实验研究了不同加工参数对桂晶片表面粗糙度和材料去除率的影响.采用扫描探针显微镜和激光数字波面干涉仪分别对加工后的硅晶片进行测量,实验结果表明:在优化实验条件下硅晶片可以获得表面粗糙度0.533nm的超光滑表面.     

An experimental study on microcutting of silicon using a micromilling machine

Micro-end-milling can potentially create desired 3D free-form surface features on silicon using ductile machining technology. A number of technological barriers must be overcome for micro-end-milling to be applied in the cutting of single crystal silicon. To produce smooth surfaces on brittle materials, such as silicon, it is important that the material be machined in the ductile mode. A major limitation of machining brittle materials is that the process of removing the material can generate subsurface damage. We have carried out an experimental study to find the optimum cutting conditions for obtaining ductile regime machining using a micromilling machine. The ductile and brittle regimes in the machining of silicon using diamond-coated end mills were demonstrated by machining grooves. The force ratio, F_t/F_c, was used to determine the milling performance on silicon. The experimental data show that the dominant ductile cutting mode was achieved when F_t/F_c?>?1.0.     

Research on unbounded abrasive polishing process with assisted ultrasonic vibration of workpiece

Ultrasonic-assisted machining was an effective method to improve the material removal quality especially to difficult-to-cut metal materials. The ultrasonic vibration was usually superimposed on the machining tool but seldom on the workpiece, although the ultrasonic vibration of workpiece could improve the processability of material more effectively. In this paper, a rectangle hexahedron ultrasonic sonotrode with optimized slots was developed as a platform to realize the assisted ultrasonic vibration of workpiece and the ultrasonic-assisted polishing process of austenitic stainless steel was also studied. The unbounded abrasive was selected as polishing medium, and the path compensation strategy of soft polishing tool was carried out for getting uniform polishing force. The orthogonal experiments were designed to study the optimization of ultrasonic polishing parameters and the relation between different types of ultrasonic polishing path and polishing quality. The results appear that the horizontal ultrasonic vibration of workpiece can reduce polishing force and improve polished surface roughness, which can also reinforce the proportion of plastic shear effect in the material removal process. The ultrasonic polishing path keeping consistent with workpiece vibration direction can get more uniform polishing force and better surface roughness. And the 45° oblique crossing ultrasonic path can get the maximum average polishing force reduction by 75.2 %.     

超磁致伸缩超声振动系统的机电转换效率研究

为提高超声振动系统的能量转换效率和功率容量,提出超磁致伸缩超声振动系统的设计方法,研究导磁体材料特性对超声系统振动性能的影响规律。采用硅钢、铁氧体和磁粉心三种磁性材料设计导磁体,并建立超声振动系统的等效电路模型;通过阻抗分析建立3种超声振动系统的阻抗圆曲线,得到谐振频率和机电转换系数等参数,提出导磁材料特性对系统机电能量转换效率的影响规律。为验证阻抗分析结果的正确性,试验测定3种超声系统在不同电压幅值激励下的振幅-电流灵敏度与频率的关系曲线,验证导磁材料参数与系统机电能量转换效率之间的关系。结果表明：高磁导率铁氧体材料可提高超声振动系统在小功率工作条件下的机电能量转换效率,而对于大功率超声振动系统而言,需要兼顾磁导率和饱和磁通密度,使导磁体工作于非磁饱和状态,以提高系统换能效率,这有助于指导不同功率大小超声振动系统的导磁体材料选择。     

Multi-discharge EDM coring of single crystal SiC ingot by electrostatic induction feeding method

A new technique of EDM coring of single crystal silicon carbide (SiC) ingot was proposed in this paper. Currently single crystal SiC devices are still of high cost due to the high cost of bulk crystal SiC material and the difficulty in the fabrication process of SiC. In the manufacturing process of SiC ingot/wafer, localized cracks or defects occasionally occur due to thermal or mechanical causes resulted from fabrication processes which may waste the whole piece of material. To save the part of ingot without defects and maximize the material utilization, the authors proposed EDM coring method to cut out a no defect ingot from a larger diameter ingot which has localized defects. A special experimental setup was developed for EDM coring of SiC ingot in this study and its feasibility and machining performance were investigated. Meanwhile, in order to improve the machining rate, a novel multi-discharge EDM coring method by electrostatic induction feeding was established, which can realize multiple discharges in single pulse duration. Experimental results make it clear that EDM coring of SiC ingot can be carried out stably using the developed experimental setup. Taking advantage of the newly developed multi-discharge EDM method, both the machining speed and surface integrity can be improved.     

An experimental investigation into the micro-electrodischarge machining behavior of p-type silicon

The present study aims to investigate the feasibility of micro-structuring in p-type silicon, using conventional die-sinking electrodischarge machining (EDM). The EDM behavior of the silicon material is studied in terms of the effect of major operating parameters on the performance characteristics during the micro-hole machining. In addition, microelectrodes are fabricated successfully on the conventional EDM machine for machining different micro-structures in silicon. Three different types of micro-structures??micro-hole, blind slots, and through slots??are fabricated in p-type silicon successfully by using optimum parameters setting. It has been observed that p-type silicon is machinable by EDM using both the polarities. Moreover, like other electrodischarge machinable materials, the selection of optimum operating parameters is very important for improved performance, as those parameters are found to influence the EDM performance of silicon significantly. Finally, it has been concluded that p-type silicon is machinable into different forms of micro-structures by understanding its electrodischarge machining behavior and by careful selection of optimum parameters.     

Design and implementation of a system for laser assisted milling of advanced materials

Laser assisted machining is an effective method to machine advanced materials with the added benefits of longer tool life and increased material removal rates. While extensive studies have investigated the machining properties for laser assisted milling(LAML), few attempts have been made to extend LAML to machining parts with complex geometric features. A methodology for continuous path machining for LAML is developed by integration of a rotary and movable table into an ordinary milling machine with a laser beam system. The machining strategy and processing path are investigated to determine alignment of the machining path with the laser spot. In order to keep the material removal temperatures above the softening temperature of silicon nitride, the transformation is coordinated and the temperature interpolated, establishing a transient thermal model. The temperatures of the laser center and cutting zone are also carefully controlled to achieve optimal machining results and avoid thermal damage. These experiments indicate that the system results in no surface damage as well as good surface roughness, validating the application of this machining strategy and thermal model in the development of a new LAML system for continuous path processing of silicon nitride. The proposed approach can be easily applied in LAML system to achieve continuous processing and improve efficiency in laser assisted machining.     

An analytical model of rotary ultrasonic milling

Rotary ultrasonic machining is currently being used as a manufacturing method for advanced ceramic materials, but its complexity has hindered its acceptance in industry. For this technology to gain wider acceptance, it must first be scientifically better understood. The majority of published rotary ultrasonic machining (RUM) papers studied the effect of RUM process parameters on machining performance and removal mechanisms for drilling of circular holes. In industries such as aerospace, the production of advanced turbine components requires machining of complex 3D features using milling strategies. The objective of this paper will be to present a new physical model based on rotary ultrasonic milling which will help provide a better scientific understanding of the process. This will be accomplished by first modeling the macro kinematics between the tool and material followed by the modeling of micro kinematics between the individual diamond grains and the material. In addition, a force model for predicting machining process forces will also be introduced and validated based on a set of experiments. The physical models will help determine the relationships between input parameters, cutting parameters, and process output parameters for rotary ultrasonic milling.     

变幅杆连接工艺对旋转超声加工质量影响的研究

超声旋转加工是一种适用于脆硬材料加工的新技术,它强化了原加工过程,其加工效率随着材料脆性的增大而提高,实现了低耗能的目标。在超声旋转加工中,超声加工工具与变幅杆的连接对超声振动共振频率和超声波加工性能有很大影响。本文在深入研究旋转超声加工基本原理的基础上,分析了旋转超声加工时能量传递系统的关键制件-变幅杆和工具杆对超声加工精度的影响,并对变幅杆和工具杆制造工艺及连接的方法进行了初步研究。     

Study of EDM cutting of single crystal silicon carbide

Electrical discharge machining (EDM) is developing as a new alternative method for slicing single crystal silicon carbide (SiC) ingots into thin wafers. Aiming to improve the performance of EDM slicing of SiC wafers, the fundamental characteristics of EDM of SiC single crystal were experimentally investigated in this paper and compared to those of steel. Furthermore, EDM cutting of SiC ingot by utilizing copper foil electrodes was proposed and its performance was investigated. It is found that the EDM characteristics of SiC are very different from those of steel. The EDM machining rate of SiC is higher and the tool wear ratio is lower compared to those of steel, despite SiC having a higher thermal conductivity and melting point. Thermal cracks caused by the thermal shock of electrical discharges and the Joule heating effect due to the higher electrical resistivity are considered to be the main reasons for the higher material removal rate of SiC. It is concluded that the new EDM cutting method utilizing a foil electrode instead of a wire electrode has potential for slicing SiC wafers in the future.     

Mathematical model for cutting force in rotary ultrasonic face milling of brittle materials

Rotary ultrasonic machining of brittle materials, such as glass, ceramics, silicon, and sapphire, has been explored in a large number of experimental and theoretical investigations. Mechanistic models have been developed to predict the material removal rate or cutting force in the rotary ultrasonic machining of brittle materials. However, most merely describe the rotary ultrasonic machining process of drilling holes in brittle materials. There are no reports on the development of a cutting force model for flat surface rotary ultrasonic machining, i.e., rotary ultrasonic face milling. This paper presents a mathematical model for the cutting force in the rotary ultrasonic face milling of brittle materials under the assumption that brittle fracture removal is the primary mode of material removal. Verification experiments are conducted for the developed cutting force model and show that the trends of input variables for the cutting force agree well with the trends of the developed cutting force model. The developed cutting force model can be applied to evaluate the cutting force in the rotary ultrasonic face milling of brittle materials.