混粉电火花镜面加工技术的研究及进展

混粉电火花镜面加工技术能够显著改善加工表面粗糙度,提高表面质量,使电火花加工作为精密模具制造的最终工序成为可能。从混粉电火花镜面加工技术的机理性研究和工艺性研究两方面,详细论述了有关研究内容和研究进展,可为今后的深入研究提供参考。     

密封圈模具的电火花成形铣削

在研究分析电火花成形铣削的工艺方法、工艺特点及适用范围的基础上,提出将其与混粉工艺相结合,应用于密封圈模具的制造,可提高加工效率,获得镜面效果的高精度型腔,使电火花加工成为模具型腔的最终精加工。     

混粉电火花加工在模具制造中的应用

通过对混粉电火花加工工艺与传统模具制造工艺的比较，从混粉电火花加工工艺的机理、表面特性、影响因素等各方面来阐述，混粉电火花加工是生产高精度、高寿命、效率的模具的最有效的工艺之一。     

大面积混粉电火花镜面加工技术的实验研究

对大面积条件下的混粉电火花镜面加工技术进行研究表明 ,加工时间、放电参数及电极表面状态都对加工表面粗糙度有一定的影响 ,通过采用合理的工艺参数 ,大面积下的混粉电火花加工表面粗糙度可达Ra0 .15μm ,所加工的三维型腔表面光亮、均匀 ,呈镜面反光效果     

镜面电火花加工技术的研究与应用

目前镜面电火花加工技术在精密型腔模具制造中逐步得以推广。文章就企业中镜面电火花加工应用的关键环节,结合实践分析了影响镜面加工性能的因素。通过控制各个工艺环节,可有效实现高质量、高效率的镜面电火花加工。对模具制造企业吸收与消化当前先进的电火花加工工艺具有实际的应用价值。     

新型精密模具表面镜面加工技术

介绍了混粉电火花与大面积脉冲电子束模具镜面加工(EBM)技术的概况,对两种技术在加工材料、加工效率、加工成本及表面质量等进行分析对比,指出两种加工技术的应用特点.为精密模具表面镜面加工提供了技术指导.     

模具光整加工技术新进展

从工艺——机械抛光、特种抛光、复合抛光，自动化——数控机床、机器人、知识库、测量，“一次过加工技术”——高频窄脉冲和展成电解加工、混粉电火花镜面加工、高速铣加工三方面对现有的模具抛光技术进行了较为详细的介绍，分析了各自的特点、适用场合及某些技术关键。     

混气电火花镜面加工的研究

概述了火花经镜面加工发展情况,提出了混气电火花镜面加工工艺,分析了混气电火花镜面加工的原理,设计了混气装置,并进行了实验,实验结果表明混气电火花加工能够有效地改善加工表面粗糙度和提高生产率。     

影响混粉电火花镜面加工效果的因素及对策

影响混粉电火花镜面加工效果的主要因素有粉末的特性、电极材料及其表面粗糙度、工件材科、电脉冲参数等。文中对这些因素影响加工效果的机理进行了说明．并针对这些因素提出在实际生产中应采取的相应工艺技术规准和要求。     

国外电火花成型加工技术

当前,世界电加工技术正向高精密、低粗糙度(镜面加工)、高速度、电极低损耗、高自动化及性能更完善等方向发展。1995年9月在北京召开了第四届国际机床展览会,参展的国外电火花成型机床,在其功能、可靠性、加工工艺指标等许多方面都有新的进步。本文根据有关资料及参观所得介绍如下:1.高速镜面加工一般镜面电火花加工的表面粗糙度R_a小于0.3μm。参展的国外主要公司都展示了镜面加工技术,目前镜面加工已达较大的面积,如Sodick公司展示了面积为200mm×200mm、R_(max)为3μm的加工样件。镜面加工主要是在放电液中加入导电粉末,三菱电机公司加硅粉,Sodick公司加含铬的钨粉,加入量约为几克至几十克每升。在镜面加工时,先在无粉的油中进行粗加工,粗加工完成后再转换到混粉油中进行镜面加工,混粉加工不用过滤,但须振动搅拌。在油中加入导电粉能实现镜面加工的原因为:(1)使放电点分散,避免了放电集中现象,防止了电弧和烧伤加工表面;(2)放电间隙增大,排屑容易,加工稳定;(3)间隙分布电容减小,放电能量小,有利于镜面加工。加入粉末后加工速度一般可提高2～5倍。在大面积加工R_a小于0.63μm时,加工速度提高6     

Surface characterization and material migration during surface modification of die steels with silicon, graphite and tungsten powder in EDM process

The present study reports the results of an experimental work carried out to evaluate the improvement in machined surface properties of die steels machined using powder mixed electric discharge machining (PMEDM) process. Two surface responses, surface finish and microhardness were analyzed for changes when machined with Si, W and graphite powders mixed in dielectric fluid. The machined surfaces were subsequently analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to study the element migration from powder, dielectric and the tool. The powder mixed with dielectric and its concentration, current and pulse on time were identified as the significant factors affecting surface finish. Brass electrode and tungsten powder resulted in good surface finish. Amongst the dielectrics used, kerosene provided a better cooling effect whereas EDM oil resulted in better surface finish. The microhardness of the machined surface was also affected by powder and its concentration, current, pulse on time and electrode material. W-Cu electrode and W powder resulted in a higher microhardness. The SEM and EDS analysis showed significant migration of material from the suspended powder, electrode and dielectric to the machined surface.     

Investigating surface properties of OHNS die steel after electrical discharge machining with manganese powder mixed in the dielectric

Although electrical discharge machining is essentially a material removal process, efforts have been made in the recent past to use it as a surface treatment method. An additive powder in the dielectric medium affects the sparking action and helps in improving the surface properties. It may melt at the high temperature of the plasma channel and alloy with the machined surface under appropriate machining conditions. Breakdown of the hydrocarbon dielectric contributes carbon to the plasma channel. In this paper, changes in surface properties of oil-hardening non-shrinkable die steel after machining with manganese powder suspended in kerosene dielectric medium have been investigated. Results show improvement in microhardness by 73%, and no microcracks on the machined surface. X-ray diffraction analysis of the machined surfaces reveals the transfer of manganese and carbon from the plasma channel in the form of manganese carbide. Quantitative analysis of chemical composition by optical emission spectrometer confirms significant increase in the percentages of manganese and carbon.     

粉末冶金零件加工研究进展

介绍了国内外粉末冶金烧结件加工的研究现状,对工艺参数优化、刀具磨损、已加工表面质量进行了详细分析,阐述了改善粉末冶金烧结件可加工性的措施:表面浸渗、添加易切削剂。分析了粉末冶金生坯加工时工艺参数对已加工表面质量的影响、生坯强度的提高以及生坯加工后的烧结件的力学性能。     

Assessment of PM-EDM cycle factors influence on machining responses and surface properties of biomaterials: A comprehensive review

Powder mixed-electro discharge machining (PM-EDM) is recently evolving machining technique which can simultaneously remove and modify the machined surface through thermo-electrical process. It is a modified form of EDM in which the conductive powder elements are added in the dielectric liquid to enhance machined surface characteristics and machining responses. The commonly used biomaterials such as 316L stainless steel, Ti-based alloy, Ni–Ti, Mg alloy, and Co–Mo–Cr alloy have excellent mechanical characteristics while the biofunction of these materials are not in satisfactory level. Due to higher hardness, brittleness, and heat resistant natures of the biomaterials, it is very challenging to machine them with conventional machining. Both the system efficiency and modified surface properties depend on the associated electrical and non-electrical factors of PM-EDM cycle. This review focuses on the influence of process factors such as current, pulse duration, tool-polarity, duty cycle, potential voltage, types of liquid, and added powder concentration on performance outputs including material removal and tool wear rate, coating thickness, coarseness, microhardness, coating adhesion bonding, biocompatibility, and resistant to corrosion. This study also discusses influence of various powders on machining and modified surface characteristics of biomaterials. The future research scopes and challenges of PM-EDM process are included in this study thoroughly.     

混粉大面积电火花加工机理的分析

根据电火花加工原理和特点,分析了传统大面积电火花加工很难获得良好粗糙度的原因,同时探讨了混粉电火花加工改善大面积加工表面粗糙度的原因,并用实践验证了混粉电火花加工能改善加工表面粗糙度     

往复运动速度规划算法对曲线磨削的影响研究

往复加工常见于磨削和刨削等金属切削中,加工过程的平稳性直接影响到产品的加工质量、能源效率乃至机床的寿命。首先探究往复（冲程）运动速度规划对运动过程平稳性的影响,在分析了常见速度规划运动学性能的基础上,针对磨削冲程运动的特点,提出通过改变急动度空间分布来降低柔性冲击对加工表面质量的影响,并设计了两种基于急动度连续的速度规划算法。在此基础上,研究了速度规划算法和磨削力平稳性、加工表面粗糙度和加工能耗间的关系,提出了通过改变加速度空间分布来降低加工能耗的方法。试验结果表明,往复运动速度规划和磨削力平稳性、加工表面粗糙度以及加工能耗均相关,通过改变急动度和加速度空间分布提高了磨削力平稳性和加工表面质量,降低了加工能耗。所提出的Ⅱ型速度规划综合表现优于其他规划,与梯形速度规划相比,切削力波动、加工表面粗糙度和电机驱动能耗均有较为显著的下降。     

Application of TOPSIS to Taguchi method for multi-characteristic optimization of electrical discharge machining with titanium powder mixed into dielectric fluid

Mixing powder into dielectric fluid in electrical discharge machining (PMEDM) is a very interesting technological solution in current research. This method has the highest efficiency in simultaneously improving the productivity and quality of a machined surface. In this study, material removal rate (MRR), surface roughness (SR), and the micro-hardness of a machined surface (HV) in electrical discharge machining of die steels in dielectric fluid with mixed powder were optimized simultaneously using the Taguchi–TOPSIS method. The process parameters used in the study included workpiece materials (SKD61, SKD11, SKT4), electrode materials (copper, graphite), electrode polarity, pulse-on time, pulse-off time, current, and titanium powder concentration. Some interaction pairs among the process parameters were also used to evaluate the effect on the optimal results. The results showed that MRR and HV increased and SR decreased when Ti powder was mixed into the dielectric fluid in EDM. Factors such as powder concentration, electrode material, electrode polarity, and pulse-off time were found to be significant in the optimal indicator (C*) and the S/N ratio of C*. Powder concentration was also found to be the most significant factor; its contribution to C* was 50.90%, and S/N ratio of C* was 51.46%. The interactions of the powder concentration and certain process parameters for C* were found to be largest. The optimum quality characteristics were MRR?=?38.79 mm³/min, SR?=?2.71 μm, and HV?=?771 HV. The optimal parameters were verified by experiment, and its accuracy was good (max error ≈13.38%). The finished machined surface under optimum conditions was also analyzed. The machined surface quality under optimum conditions was good. In addition, the results of the study showed the TOPSIS limitations of TOPSIS in a multi-criteria optimization problem.     

50%SiC/Cu复合材料电火花加工研究

采用粉末冶金工艺制备了50%SiC/Cu复合材料.研究了电参数对线切割加工SiC颗粒增强Cu基复合材料的加工速度和表面质量的影响规律.用扫描电子显微镜分析了复合材料加工表面的形貌特征.结果表明,选用较大的峰值电流和较短的脉冲宽度,可对50%SiCp/Al复合材料进行较理想的线切割加工     

Effect of cutting speed on surface integrity and chip morphology in high-speed machining of PM nickel-based superalloy FGH95

High-speed machining is being recognized as one of the key manufacturing technologies for getting higher productivity and better surface integrity. FGH95 powder metallurgy superalloy is a kind of nickel-based superalloy which is produced by near-net-shape technology. With increasing demands for high precision and high performance of FGH95 components in aerospace industry, it is essential to recognize that the machined surface integrity may determine machined part service performance and reliability. Then, little is known about the machined surface integrity of this superalloy. Thus, the surface integrity in high-speed machining of FGH95 is investigated in this paper. Experiments are conducted on a CNC milling center with coated carbide tools under dry cutting conditions. The surface integrity is evaluated in terms of surface roughness, microhardness, and white layer. The influence of cutting speed on chip morphology is also investigated. Experiment results show that surface integrity and chip morphology of FGH95 are very sensitive to the cutting speed. When cutting speeds are below 2,400?m/min, the values of surface roughness have little variation, while when cutting speeds are in the range of 2,800–3,600?m/min, the values of surface roughness are higher than that of other cutting speeds. Severe work hardening is observed resulting from high-speed machining of FGH95 superalloy. The higher the cutting speed, the higher the surface hardness. When cutting speeds are in the range of 2,800–3,600?m/min, the white layer thickness is slightly higher than that of other cutting speeds. In high-speed machining of FGH95, the chip is segmented and has a typical sawtooth shape. The degree of serrated chip increases with the cutting speed. When the cutting speeds exceed 2,400?m/min, serrated chips change into fragment chips.     

Topography and microstructure of the cutting surface machined with abrasive waterjet

Abrasive waterjet (AWJ) technology has been widely used for cutting materials in precision machining. The present paper reports the surface topography and microstructure of the cutting surfaces machined by AWJ. Four different kinds of ductile metallic materials were used for preparation of specimens. With the AWJ processing technique, smooth surfaces were easily obtained with a lower surface roughness about 2 to 3 μm. By comparing the microhardness of the specimens with the control surface sample obtained by wire electrodischarge machining, it is found that there is no heat-affected zone on the cutting surfaces machined by AWJ. By observing the surface morphology and microstructure, the features of friction and wear marks are revealed. The results show that a smooth cutting surface is more easily obtained on hard materials, while erosions on soft material surfaces are more serious. All scratches have a clear consistent direction, under the action of mechanical abrasive wear.