粉末工作液电火花加工

作者采用特制的实验装置对掺入硅粉的放电加工面生成机理进行了实验性探讨,并对比分析了煤油工作的粉末工作液电火花加工的效果,得出粉末工作液电火花加工能够改善表面粗糙度的结论。     

大面积混粉电火花加工机理探讨

论述了大面积混粉电火花加工的机理，分析了大面积混粉电火花加工能提高加工表面粗糙度的原因，指出放电蚀坑大儿浅，并且在加工表面分布均匀是大面积混粉电火花加工提高加工表面粗糙度的根本原因，通过在普通和混粉工作液中的大面积电火花加工实验对比，证明以上结论的正确性。     

混粉电火花加工工艺实验

研究采用混粉工作液的电火花加工原理,提出了适合于混粉加工的工艺参数,通过电火花加工实验,降低了加工零件的表面粗糙度值。     

激光微涂敷层的电火花后处理及其加工性能

分析、测量了不同加工条件下的材料去除率、相对电极损耗和电火花加工表面粗糙度,并研究了表面微裂纹和微硬度分布。实验结果表明,不同的材料具有类似的电火花加工性能,材料去除率随脉冲电流的增加而增加,峰值电流比脉冲宽度对表面粗糙度的影响更显著。研究结果对于选择合适参数进行电火花后处理具有重要意义。     

不同电极材料对电火花加工表面粗糙度影响的试验研究

为了研究不同电极材料对加工表面粗糙度的影响,选用紫铜、石墨和钨铜合金三种电极,在煤油和混粉介质两种工作液中,设定电压为35V、脉冲宽度和脉间宽度均为50μs,用1A、5A、10A、15A等四种电流进行试验,对比分析加工工件的表面粗糙度,得出在煤油介质中紫铜电极加工的表面粗糙度最小、混粉介质中钨铜合金电极加工效果最好的结论;对表面形态和再铸层分析,得出石墨电极加工因再铸层区域厚导致表面粗糙度较大、钨铜合金电极加工的再铸层厚度较小使得表面粗糙度值较低等结论,为生产实践中电极材料选择提供试验依据。     

混气与混粉电火花加工机理的分析

分别介绍了混粉电火花加工和混气电火花加工的特点，以及关于混粉和混气电火花加工的机理解释，对这两种加工方法的机理进行了分析比较，从而得出两种加工方法侧重点不同的结论，即同普通电火花加工相比，混粉电火花加工易于降低表面粗糙度，而混气电火花加工速度相对较快。     

线切割加工条件对模具零件表面粗糙度的影响

为改善快走丝电火花线切割加工的表面粗糙度,提高模具加工的质量和使用寿命,分析了快走丝电火花线切割加工条件中放电参数、工作液和电极丝对零件表面粗糙度的影响,并在此基础上提出了改善零件表面粗糙度的相应措施和方法。     

水基切削液对线切割加工的影响

工作液作为高速走丝电火花线切割加工的重要组分，除了完成冷却、排屑等功能外，还作为放电介质直接参与加工，所以其本身对加工工艺指标影响很大。实践证明，电火花加工在液体介质中进行最稳定，并且工作液对加工工艺指标（如切割速度、表面粗糙度，加工精度等）影响很大。电火花线切割加工使用的工作液应具有加工性能好、使用寿命长、环境污染小、对人体无害、价格便宜等技术要求。     

充磁与未充磁烧结钕铁硼电火花加工对比试验研究

钕铁硼硬度高、脆性大,且充磁后具有高磁性力.电火花加工是钕铁硼的重要加工方法.为探寻充磁与未充磁烧结钕铁硼在电火花加工过程中的工艺差异和规律,采用单因素试验方法,开展对比试验,研究放电参数(脉冲宽度、峰值电流和脉冲间隔)对充磁与未充磁烧结钕铁硼的材料去除率、表面粗糙度和重铸层的影响.结果 表明:随脉冲宽度的增加,充磁烧结钕铁硼的材料去除率增大,而未充磁烧结钕铁硼的材料去除率先增大后略有减小,充磁与未充磁烧结钕铁硼表面粗糙度值均增大,重铸层均增厚且内部出现裂纹;随峰值电流的增加,两者材料去除率和表面粗糙度值均增大;随脉冲间隔的增加,两者材料去除率和表面粗糙度值均减小;在较大的放电参数值下,充磁烧结钕铁硼的材料去除率和表面粗糙度明显优于未充磁烧结钕铁硼.     

充磁与未充磁烧结钕铁硼电火花加工对比试验研究

钕铁硼硬度高、脆性大,且充磁后具有高磁性力.电火花加工是钕铁硼的重要加工方法.为探寻充磁与未充磁烧结钕铁硼在电火花加工过程中的工艺差异和规律,采用单因素试验方法,开展对比试验,研究放电参数(脉冲宽度、峰值电流和脉冲间隔)对充磁与未充磁烧结钕铁硼的材料去除率、表面粗糙度和重铸层的影响.结果 表明:随脉冲宽度的增加,充磁烧结钕铁硼的材料去除率增大,而未充磁烧结钕铁硼的材料去除率先增大后略有减小,充磁与未充磁烧结钕铁硼表面粗糙度值均增大,重铸层均增厚且内部出现裂纹;随峰值电流的增加,两者材料去除率和表面粗糙度值均增大;随脉冲间隔的增加,两者材料去除率和表面粗糙度值均减小;在较大的放电参数值下,充磁烧结钕铁硼的材料去除率和表面粗糙度明显优于未充磁烧结钕铁硼.     

气体放电加工基础工艺试验研究

采用单因素法进行了基本的工艺参数(电参数、伺服参考电压等)对气体介质放电加工性能影响的试验研究。试验结果表明:气体介质的放电加工适于采用正极性加工。在试验加工的范围内,工件的蚀除速度和表面粗糙度值随脉冲宽度和峰值电流的增加而增加,随脉冲间隔的增加而减小。极间并联合适的电容能够使加工速度和加工表面粗糙度有所改善,并对此现象进行了分析。对于某一确定的加工参数,存在一个较佳的伺服参考电压值,使加工性能较为稳定。工具电极具有较高的旋转速度能够使气体放电加工性能得到提高。使用氧气介质能够实现快速电火花加工,并根据不同气体的物理性能对不同气体介质的加工性能进行了分析。工件表面显微硬度测试结果表明:空气中放电加工的工件的表面硬度比基体硬度高,比煤油中加工的工件表面硬度低。     

水包油型乳化液钛合金TC4电火花加工特性研究

为解决钛合金在煤油介质中电火花加工效率低及在蒸馏水介质中加工表面质量差的问题,提出利用乳化剂将煤油和蒸馏水超声振动后形成水包油型乳化液作为工作介质的加工方法。分别以煤油、水包油型乳化液和蒸馏水为工作介质,对钛合金TC4进行放电加工试验,从加工效率、电极相对损耗率和表面质量三个方面,对比研究了不同工作介质中钛合金电火花加工的特性。试验结果表明：水包油型乳化液中的加工效率是煤油中加工效率的两倍左右,工件表面粗糙度值Ra比蒸馏水中的Ra值减小了15%~20%,加工后工件表面微裂纹较少,表面较平整,但其电极相对损耗率高。     

Feasibility study of micro-slit EDM machining using pure water

This study addresses micro-slit EDM machining feasibility using pure water as the dielectric fluid. Experimental results revealed that pure water could be used as a dielectric fluid and adopting negative polarity EDM machining could obtain high material removal rate (MRR), low electrode wear, small slit expansion, and little machined burr, compared to positive polarity machining. In comparing kerosene versus pure water, pure water was observed to cause low carbon adherence to the electrode surface. Also discharge energy does not decrease and the discharge processes are not interrupted. Therefore, MRR was higher, and related electrode wear ratio compared to kerosene use was lower. In a continual EDM with multi-slit machining, kerosene will cause carbon element adherence, creating an initially high MRR and electrode wear, with rapid decline. However, pure water will not cause carbon element adherence on the electrode surface, so MRR and electrode wear is always stable in this process.     

MEASUREMENT OF HYDROGEN CONTENT IN ELECTRICAL DISCHARGE MACHINED COMPONENTS

During electric discharge machining (EDM) process, localized high temperature electric discharges occur in the presence of hydrocarbon dielectric such as kerosene. Hydrogen that can get incorporated into the workpiece during the process can dramatically affect the mechanical properties of the machined workpiece. In the present work the hydrogen content in workpieces machined by EDM and electric discharge abrasive drilling (EDAD) have been measured by a relatively new diagnostic technique called Elastic Recoil Detection (ERD), which utilizes He⁺ ions of mega electron volt energy obtained from a particle accelerator. Workpieces made up of high-speed steel and cemented carbide were machined at different pulse-on-times, and their hydrogen content was measured. From the experiments reported in this paper, it is concluded that hydrogen diffusion takes place in the workpiece surface.     

空气中微细电火花沉积与去除可逆加工技术研究

论述了一种新的电火花加工方法。它使用通用的电火花成形加工机床,利用常见的电极材料,在空气介质中,通过脉冲放电在工件表面上沉积生长电极材料,再通过反转极性和适当的轨迹控制对所生成的沉积材料进行有选择的去除加工,进而实现材料的生长与去除可逆加工。通过对电火花加工理论的研究,预测和论证了实现这一新加工方法的可能性和实现条件。通过试验成功地将钢、铜和钨三种电极材料沉积到工件上,形成直径为 100~240 mm、高度为1 000~2 500 mm的微小圆柱体。并对沉积物进行了选择去除,实现了在同一设备上的可逆电火花加工。对沉积材料的致密性、硬度及其与工件的结合强度等进行了系统的分析,表明沉积物组织致密、坚硬,可以满足功能材料的要求。     

基于电火花加工方法的表面改性技术研究

研究了一种在普通电火花加工机床上实现金属工件表面改性的新方法。它是在传统电火花加工方法的基础上，采用TiC-Co半烧结体电极和普通煤油工作液，在工件表面形成一层硬质陶瓷层，从而达到改善工件表面性能的目的，这种新方法被称之为放电沉积。对放电沉积原理进行了探讨，在大量试验的基础上，总结了放电沉积的工艺方法。通过扫描电镜、电子探针、X射线衍射分析、摩擦磨损等试验，对形成的沉积层特性进行了定量和定性分析。最后利用该方法在普通的高速钢车刀上进行了初步应用。试验与分析表明，该方法是一种极具潜力的金属表面改性方法。     

Sinking EDM in water-in-oil emulsion

In this paper, a new type of sinking electric discharge machining (EDM) dielectric–water-in-oil (W/O) emulsion is proposed, and the machining characteristics of W/O emulsion are investigated by comparing with that of kerosene. In the experiments, machining parameters such as the dielectric type, peak current, and pulse duration are changed to explore their effects on machining performance, including the material removal rate (MRR), relative electrode wear rate (REWR), and surface roughness. Experimental results revealed that W/O emulsion could be used as the dielectric fluid of sinking EDM and adopting long pulse duration and large peak current could lead to obtaining higher MRR than kerosene. Compared with kerosene, W/O emulsion is observed to cause lower carbon adhered to the electrode surface. Therefore, its REWR is higher. Statistics of the discharge waveform show that more stable discharge processes can be obtained by using W/O emulsion compared with kerosene. Furthermore, W/O emulsion is more economical and more environmentally friendly than kerosene, and it could be an alternative to kerosene in sinking EDM application.     

An experimental investigation of tool wear in electric discharge machining

In this study, the variations of geometrical tool wear characteristics – namely, edge and front wear – and machining performance outputs – namely, workpiece removal rate, tool wear rate, relative wear and workpiece surface roughness – were investigated with varying machining parameters. Experiments were conducted using steel workpieces and round copper tools with a kerosene dielectric under different dielectric flushing conditions (injection, suction and static), discharge currents and pulse durations. The experiments have shown that machining parameters and dielectric flushing conditions had a large effect on geometric tool wear characteristics and machining performance outputs. Additionally, published research on tool wear is presented in detail in this study.     

Comparative study of different dielectrics for micro-EDM performance during microhole machining of Ti-6Al-4V alloy

In microelectrodischarge machining (micro-EDM), dielectric plays an important role during machining operation. The machining characteristics are greatly influenced by the nature of dielectric used during micro-EDM machining. Present paper addresses the issues of micro-EDM utilizing different types of dielectrics such as kerosene, deionized water, boron carbide (B₄C) powder suspended kerosene, and deionized water to explore the influence of these dielectrics on the performance criteria such as material removal rate (MRR), tool wear rate (TWR), overcut, diameteral variance at entry and exit hole and surface integrity during machining of titanium alloy (Ti-6Al-4V). The experimental results revealed that MRR and TWR are higher using deionized water than kerosene. Also, when suspended particles, i.e., boron carbide-mixed dielectrics are used, MRR is found to increase with deionized water, but TWR decreases with kerosene dielectric. Further analysis is carried out with the help of scanning electron microscope (SEM) micrographs, and it is found that the thickness of white layer is less on machined surface when deionized water is used as compared to kerosene. Also, a comparative study of machining time has been carried out for the four types of dielectrics at different machining parametric settings. Furthermore, the investigation on the machined surface integrity and wear on microtool tip have also been done in each type of the dielectrics with the help of SEM micrographs and optical photographs. Hence micro-EDM machining on Ti-6Al-4V work material with B₄C-mixed dielectrics is performed in the investigation and reported the performance criteria of the process. It can be concluded from the research investigation that there is a great influence of mixing of boron carbide additive in deionized water dielectrics for enhancing machining performance characteristics in micro-EDM during microhole generation on Ti-6Al-4V alloy.     

The Effect of Cutting Parameters on Workpiece Surface Roughness in Wire EDM

In this study, the variation of workpiece surface roughness with varying pulse duration, open circuit voltage, wire speed and dielectric fluid pressure was experimentally investigated in Wire Electrical Discharge Machining (WEDM). Brass wire with 0.25 mm diameter and SAE 4140 steel with 10 mm thickness were used as tool and workpiece materials in the experiments, respectively. It is found experimentally that the increasing pulse duration, open circuit voltage and wire speed, increase the surface roughness whereas the increasing dielectric fluid pressure decreases the surface roughness. The variation of workpiece surface roughness with machining parameters is modelled by using a power function. The level of importance of the machining parameters on the workpiece surface roughness is determined by using analysis of variance (ANOVA).