电解线切割加工技术试验研究

分析了应用电解线切割加工工艺在厚不锈钢板上加工高深宽比结构的可行性。为解决加工高深宽比结构时的排屑问题,在分析该工艺特点的基础上,采用了轴向冲液的方法。在自行搭建的加工系统中,进行了不同加工参数的一系列试验,以研究加工电压、电极丝进给速度、电解液浓度和冲液速度对该工艺的影响。最后,对电解线切割加工参数进行优化,加工出了缝宽为160μm、深宽比高达30的微型花键。     

微通道结构带状电极电火花加工方法研究

针对大厚度、高深宽比金属微通道结构加工的难题,提出一种带状电极电火花加工方法,利用厚度30～100 μm的带状电极,在金属基体上高效制造微通道结构。研究了带状电极电火花加工机理,建立了带状电极在加工间隙中的运动模型,分析了影响带状电极运动的主要因素,搭建了带状电极电火花加工装置,开展了微通道结构带状电极加工实验研究,获得了带状电极电火花加工基础工艺规律。利用带状电极电火花加工方法成功加工出的具有200条微通道的反应器结构和44×45微换热器阵列结构,表明带状电极电火花加工可以实现窄宽度(100 μm以下)、大厚度(35 mm以上)、高深宽比(10以上)和高精度(缝宽标准差3 μm以内)的大批量微通道结构的高效加工,相关方法和技术有望在微模具、微散热器、微反应器等领域获得推广和应用。     

基于脉冲电源的金属电化学线切割工艺研究

为了提高金属电化学线切割精度,将脉冲电源应用到切割加工中,根据电化学加工原理,并以切割缝宽为切割效果的评价标准,建立了脉冲电源切割理论模型,得出了影响缝宽变化的工艺参数,主要有:电源的电压幅值、脉冲宽度、占空比和进给速度等。并在此基础上对参数进行了优化加工实验。研究结果表明,在保证加工稳定的条件下,通过降低电压、调小脉冲宽度和占空比的方法,加工出的切割缝宽比直流电源加工出的缝宽明显减小,该方法将有望直接用于小尺寸零件的加工。     

侧壁绝缘电极脉冲电解加工的实验研究

采用侧壁绝缘电极进行电解加工可以约束加工间隙内的电场,减小杂散腐蚀,提高定域性,有着良好的应用前景。从实验出发,利用侧壁绝缘的工具电极以Na NO3为电解液对0Cr18Ni9不锈钢进行窄缝的脉冲电解加工,观测不同脉冲电压峰值、脉冲频率与占空比下的窄缝出入口和它们的宽度差。结果表明:出入口缝宽与出入口宽度差均随着脉冲电压峰值、占空比的增大而增大,随着脉冲频率、工具电极进给速度的增大而减小。     

用高转速微电极电解钻削深小孔

针对难切削材料的深小孔加工,提出一种有效排屑、迅速补充电解液的新工艺——高转速微螺旋电极电解钻削加工工艺,并对该工艺进行了机理分析与试验研究。研究了电极转速、电压、脉冲频率、进给速度等工艺参数对深小孔电解钻削加工精度和稳定性的影响,提出合理匹配上述参数可在较高加工效率下获得高的加工精度和加工稳定性。基于硬质合金微螺旋电极用自行研制的高精度微细电解系统成功地在高温镍基合金GH4169上加工出了一组孔径小于0.5mm、深径比大于10、形貌较好,锥度较小,侧壁陡直,进出口边缘锐利的深小孔。试验结果表明,高速电解钻削加工工艺在深小孔加工方面很有潜力。     

方形截面微沟槽电解铣削试验研究

针对一些方形截面微沟槽的加工,采用管电极外壁电解铣削的加工方法。利用外径为0.5 mm的管电极在304不锈钢上进行电解铣削加工方形截面微沟槽的试验,通过设计单因素试验重点研究了电解液压强、脉冲频率以及占空比对方形截面微沟槽尺寸的影响规律。并在优化参数电解液压强为0.3 MPa,电压为6 V,频率为13 kHz,占空比为30%的参数下,加工出了槽深为0.55 mm,槽宽为0.68 mm,单边平均侧面间隙为89.21μm的方形截面微沟槽。     

镍基高温合金微细电解铣削加工实验研究

针对高深宽比、复杂结构的微型腔,提出了分层电解铣削的工艺。在三轴联动微细加工平台上制作了柱状的微细电极,并在镍基高温合金上进行了微细电解铣削加工实验。研究了加工电压、脉冲参数、不同电极直径对加工精度的影响规律,成功地加工出二维结构和三维型腔。该工艺加工精度高、加工稳定性好。     

几种最新加工微阵列方法的比较

分别介绍了使用LIGA技术、微细电火花线切割技术(μ-WEDM)、微磨技术、组合式加工技术加工微阵列的最新方法.使用移动LIGA技术加工微针阵列、微细电火花技术加工复杂的三维微阵列电极、微磨技术加工微锥塔阵列、和UV-LIGA技术与微细电火花技术组合加工微阵列电极的工艺方法.主要论述各种方法加工高深宽比阵列结构的原理及其优缺点以及加工中的效率、成本等问题.     

旋转电解加工试验研究

针对常规机加工难以加工高硬度的金属材料,提出了一种旋转电解加工沟槽的方法,研制了一台实现XYZ三轴进给运动和主轴旋转运动、利用换向器实现间断式直流电源的旋转电解加工装置。以不锈钢金属为试验研究对象,加工电压、电极转速和进给速度为试验因素,进行旋转电解加工试验。试验结果表明:电解加工过程中,采用较低的电压、较高的电极转速以及中等的进给速度能够使试验结果表现的更为满意。     

纯铜窄缝式电极电火花线切割加工试验研究

窄缝式电极可以代替凹槽式电极用于电火花成形微凸起结构.为研究纯铜窄缝式电极电火花线切割加工性能的影响规律,以峰值电流、脉冲宽度、脉冲间隔、间隙电压为试验因素,设计进行了正交试验.研究了各试验因素对切缝宽度、切割速度的影响关系,采用信噪比和灰关联度分析方法对多工艺目标进行优化参数组合.试验结果表明:各因素对切缝宽度影响强弱依次为,间隙电压、脉冲宽度、脉冲间隔、峰值电流;对切割速度影响强弱依次为,脉冲宽度、脉冲间隔、间隙电压、峰值电流,其中脉冲宽度、脉冲间隔对切割速度的影响起主导作用.脉冲宽度20μs、脉冲间隔40μs、峰值电流8档、间隙电压6档为最优组合参数,为纯铜窄缝式电极的制作提供理论指导.     

Wire electrochemical machining using reciprocated traveling wire

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness.     

Micro wire electrochemical machining with an axial electrolyte flow

Micro wire electrochemical machining is a useful technique to produce high-aspect-ratio slit micro-structures. To improve processing stability, the axial electrolyte flow is adopted to renew electrolytes in the machining gap. A wire electrochemical micro-machining system with an axial electrolyte flow unit is developed. A mathematical model of tool feed rate is presented. To investigate the influence of electrolyte flow on processing stability and machining efficiency, comparative experiments were carried out. The influence of applied voltage and electrolyte concentration on machining accuracy is studied and the parameters such as electrolyte flow rate and applied voltage are optimized. Low initial machining gap is applied to decrease the stray current machining in the initial machining period. With the optimal parameters, the high-aspect-ratio micro spline and curved flow channel with the slit width of 160?μm have been fabricated on 5-mm-thick stainless steel (0Cr18Ni9). The width of the slit is uniform and the aspect ratio is 31.     

An investigation into wire electrochemical micro machining of pure tungsten

Tungsten-based microstructures have attracted great interest in many industrial advanced applications. Nevertheless, with a disadvantageous combination of high hardness, toughness and brittleness, the micro machining of pure tungsten poses significant difficulty. In this paper, an investigation into the wire electrochemical micro machining (WEMM) of pure tungsten at low alkaline electrolyte concentration and small pulse duration is presented. Under the optimal machining conditions, tungsten-based microstructures with a side gap of 4 μm, slit width of 18 μm and aspect ratio of 5.6, as well as with a side gap of 5 μm, slit width of 20 μm and aspect ratio of 15, were obtained. In order to improve productivity in the machining of multi-slit microstructures, multi-wire electrochemical micro machining of tungsten was introduced. Using a 3-wire electrode, a 9-slit microstructure with a slit width of approximately 24 μm was produced and the machining efficiency was improved by a factor of three. The results revealed that it was a promising method for the fabrication of tungsten-based periodic or quasi-periodic microstructures, such as the gratings used in the X-ray absorption contrast system of imaging.     

An experimental study on micro wire-EDM of polycrystalline diamond using a novel pulse generator

This paper presents a new pulse generator for cutting of polycrystalline diamond (PCD) by micro wire electrical discharge machining (micro wire-EDM). The pulse generator using anti-electrolysis circuitry and digital signal processor-based pulse control circuit was developed to suppress damages on the machined surface of PCD while achieving stable machining. A novel pulse control method was proposed to provide high-frequency pulse control signals with a period of off duty cycle for reionization of the dielectric in the spark gap so as to reduce the consecutive occurrence of short circuits. A series of experiments were carried out to investigate the effect of open voltage on machining performance in terms of material removal rate, slit width, thickness of the damaged layer on machined surface, and surface finish. An increase of open voltage increases peak current, thus producing greater discharge energy and, thereby, contributing to improvements in material removal rate, but leading to larger slit width and thickness of the damaged layer and worse surface finish. Experimental results not only demonstrate that the developed pulse generator could achieve satisfactory machining results but also have verified the applicability of this new technique in micro wire-EDM.     

高质量玻璃微孔电化学放电加工模型及试验

超白玻璃是一种超透明低铁玻璃,因其具有优越的物理、光学性能,而广泛应用于精密电子、高档汽车及太阳能光伏发电领域。由于其本身的硬脆特性,玻璃微孔的出口极易破损,为提高玻璃微孔的加工定域性,降低微孔出口破损的可能性,对微细电化学放电钻削加工工艺进行了研究与优化。首先,根据电化学放电原理,探讨了气膜的形成和材料去除机理,分析了放电能量对玻璃微孔加工工艺的影响,建立了单位时间电化学放电加工能量控制模型;其次,试验分析了电压幅值、占空比、脉冲频率、进给速度等主要参数对微孔入口直径和出口质量的影响;最后,通过优化后的加工参数在厚度为300μm的超白玻璃试件上,成功加工得到入口直径为172μm、出口直径为167μm的3×3微孔阵列结构,出口无破损现象。实验结果表明,基于脉冲能量控制的微细电化学放电钻削工艺在玻璃微孔加工方面很有潜力。     

Improvement of wire electrical discharge machining efficiency in machining polycrystalline silicon with auxiliary-pulse voltage supply

This study proposes a novel pulse voltage configuration, auxiliary-pulse voltage, for wire electrical discharge machining (WEDM) of polycrystalline silicon (polysilicon) used in solar cell production. It is developed with the objectives of reducing material waste due to the large kerf loss as well as achieving greater efficiency and better quality compared with conventional machining approaches. Experimental results show that compared with conventional-pulse voltage supply, the auxiliary-pulse voltage mode can avoid delay in electrical discharge during pulse-on time. Enhanced frequency of effective discharge for machining would increase machining speed, which would in turn reduce machining groove width, and obtain better surface roughness. In addition, parameters of significant influence on machining characteristics were examined with the Taguchi method, and the optimal combination levels of machining parameters were determined. In sum, our findings reveal that WEDM with auxiliary-pulse voltage supply is an effective approach to machining polysilicon with good quality and high efficiency achieved.     

Research of micro EDM/ECM method in same electrolyte with running wire tool electrode

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C₁, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.     

Study of the current signal and material removal during ultrasonic-assisted electrochemical discharge machining

Electrochemical discharge machining (ECDM) is a cost-effective machining process used to shape non-conductive materials such as glass and ceramics. The process can overcome poor machinability of hard and brittle materials. Different types of physical phenomena can be added to the ECDM components to improve the machining efficiency. As the main target of this paper, ultrasonic vibration was integrated to the cathode of the ECDM process (UAECDM), which resulted in vibration concentration only to the machining zone. In order to design the experimental configuration, modal analysis was used. Machining speed was the main output of this investigation. Gas film and electric discharge were two main physical phenomena during ECDM. The thickness of gas film, location, and pattern of discharges were determined, experimentally. Also, current signal was a useful tool that could record significant details of involved mechanisms and phenomena during machining. Images of gas film showed that the application of ultrasonic vibration decreased the thickness of gas film by 65%. In addition, the vibration amplitude of 10 μm created the most uniform current signal, which had a considerable effect on the material removal rate (MRR). Results showed that all levels of vibration amplitude increased the machining speed during discharge and hydrodynamic regimes of the machining process.     

选择性激光烧结设备管式辐射加热数值建模与计算

为了分析选择性激光烧结系统预热温度场分布不均的成因,对HRPS系列选择性激光烧结系统采用的管式辐射加热系统进行了数学建模,通过数值计算获得了不同安装高度下辐射热源对工作腔内各点的热量分布情况及均匀度变化曲线,也获得了最优的安装高度。这种数值建模的量化分析方法为开发辐射加热预热装置提供了有益的借鉴和分析思路。