用正交试验分析电参数对小孔圆柱度的影响

为实现电火花加工小孔圆柱度误差的合理控制,通过工艺试验研究了放电参数与小孔圆柱度间的规律。提出了多截面直角坐标测量方法,用线切割对已加工小孔的工件进行轴向和径向切割,以产生反映小孔特征的母线基准和圆基准;然后,用万能工具显微镜对这两个基准上的特征点进行测量,最终实现小孔圆柱度的定量评定。在此基础上,采用正交试验研究了放电参数(开路电压、电流,脉宽,脉间,抬刀周期)对小孔圆柱度的影响。结果表明,脉宽对圆柱度的影响最为显著,开路电压次之,其余3个参数的影响较弱;实验获得了以圆柱度误差最小为评价目标的一组放电参数:开路电压110V,电流0.6A,脉宽150μs,脉间120μs,抬刀周期1+2s。验证实验得到了平均半径为0.30184mm的小孔,其圆柱度误差为0.021mm,说明用该方法控制电火花加工小孔的圆柱度是有效的。     

正交磁场对电火花单脉冲放电间隙的影响

通过普通电火花单脉冲放电（EDM）与磁场辅助电火花单脉冲放电（MF-EDM）放电间隙对比试验,分析得出不同磁感应强度、开路电压、放电电容及电极外伸端长度对磁场辅助电火花加工放电间隙的影响规律。试验发现：随着磁感应强度的增大,放电间隙增大;开路电压和放电电容对放电间隙的影响较小;随着电极外伸长度的增大,放电间隙变小。最后对试验数据进行部分析因分析,得出磁场辅助电火花加工中影响放电间隙的主要因素为磁感应强度、电极外伸长度及其交互耦合作用。     

电火花微小孔加工工艺参数的优化研究

由于目前对电火花放电机理认识的有限性而使参数优化成为电火花加工中的难点之一,特别是多项工艺指标要求下的参数优化问题更是缺乏理论指导和具体应用方法。因此,在用正交试验法研究了电火花微小孔加工中放电参数和非放电参数对加工速度、电极损耗和孔径间隙等各单项工艺指标的影响规律的基础上,采用灰色相关性理论,重点解决了多项工艺指标下的参数优化这一难点问题,简化了优化过程,得出了优化的参数组合方案。     

SLS烧结参数对原型精度影响的正交试验分析

通过对轴对称圆柱孔等典型几何形状的烧结成型,研究了SLS中激光功率、加热温度以及切片厚度这三个烧结参数对圆柱孔形位公差以及直径和圆柱度的误差的影响。采用正交试验方法,在两种不同的切片方式下,分析了各种误差产生的主要原因,以及获得较高原型精度的工艺参数值。     

基于正交试验的电火花加工工艺效果试验分析

通过正交试验分析,探讨电火花成形加工中影响加工效果的主要因素,阐述了脉冲峰值电流、脉冲宽度及脉冲间 隔等对加工速度、加工表面粗糙度及工具电极损耗的影响关系,对解决电火花加工实践中工艺参数优化问题具有一定的 理论和实践意义。     

应用正交试验优化铣削参数及降低能耗研究

铣削加工是一个复杂的能量消耗的过程,可以通过选取合理的铣削参数,降低铣削加工过程中设备的能量消耗。本研究将铣削加工过程的能耗简化为铣削加工功率和时间的线性关系,经过铣削试验,获得在不同铣削参数下的铣削设备功率消耗及铣削加工时间;应用正交试验设计的方法,将选取的铣削参数做进一步的优化,从试验中可以看出不同的铣削参数对铣削设备输出功率的影响;同时,对不同铣削参数下的加工时间进行了对比分析。试验表明,在选取的铣削参数中,每齿进给量对铣削设备加工时的输出功率和加工时间影响最大,其次是切削速度,影响最小的是背吃刀量。从而对铣削参数进行优化选取,在保证加工效率及质量的前提下,将铣削设备能耗降至最低。     

用正交试验法整定PID控制器参数

提出了用正交试验法整定ＰＩＤ控制器参数的程序化方法,从理论上证明了该程序是收敛的,结合在水轮机调速器频率闭环ＰＩＤ参数整 应用结果,表明该方法简单可行,性能指标灵活,只需进行较少试验,就可选出有利的参数组合,并且能在各因素中找出影响指标的主要因素。特别适用于复杂工业系统的ＰＩＤ控制器等多参数控制器参数的工程整定。     

运用正交试验法优化切削参数

产品质量是企业的生命,为了设计出能满足用户要求的产品和改善现有产品的质量,往往都要做大量的试验研究工作,认识探求客观事物的内部规律。下面,本人就运用正交试验法合理选择切削用量、提高产品加工质量作一些探讨。 1.正交试验法有关概念的引入 正交试验法是利用数理统计学观点,应用正交性原理,从大量的试验中挑选适量的具有代表性、典型性的试验点,根据“正交表”来合理安排试验的一种科学方法。     

Scale effects and a method for similarity evaluation in micro electrical discharge machining

Electrical discharge machining(EDM) is a promising non-traditional micro machining technology that offers a vast array of applications in the manufacturing industry. However, scale effects occur when machining at the micro-scale, which can make it difficult to predict and optimize the machining performances of micro EDM. A new concept of “scale effects” in micro EDM is proposed, the scale effects can reveal the difference in machining performances between micro EDM and conventional macro EDM. Similarity theory is presented to evaluate the scale effects in micro EDM. Single factor experiments are conducted and the experimental results are analyzed by discussing the similarity difference and similarity precision. The results show that the output results of scale effects in micro EDM do not change linearly with discharge parameters. The values of similarity precision of machining time significantly increase when scaling-down the capacitance or open-circuit voltage. It is indicated that the lower the scale of the discharge parameter, the greater the deviation of non-geometrical similarity degree over geometrical similarity degree, which means that the micro EDM system with lower discharge energy experiences more scale effects. The largest similarity difference is 5.34 while the largest similarity precision can be as high as 114.03. It is suggested that the similarity precision is more effective in reflecting the scale effects and their fluctuation than similarity difference. Consequently, similarity theory is suitable for evaluating the scale effects in micro EDM. This proposed research offers engineering values for optimizing the machining parameters and improving the machining performances of micro EDM.     

大深径比微小深孔超声电火花加工工艺研究

针对难加工材料的大深径比微小深孔加工这一工艺难题,设计并制造了基于工件振动的超声电火花复合加工装置。该装置包括一个已优化的压电振子和一台普通电火花机床。为提高加工效率,对压电振子进行了优化分析,使压电振子具有合适的纵振模态、固有频率和较大的振幅,压电振子中陶瓷片具有合理地安装位置。选择模具钢作为加工材料进行大深径比微小深孔的加工实验,比较研究了超声电火花复合加工装置和普通电火花机床加工大深径比微小深孔的加工效率。实验表明,超声电火花复合加工装置的加工效率更高。研究了超声激励电压、脉冲电流、脉冲宽度以及脉冲间隙等参数对大深径比微小深孔加工效率的影响,得出各参数较优的设置值。根据实验结果可以看出,超声电火花复合加工装置可以有效地加工出直径为0.5mm、深径比为60的微小深孔,适用于难加工材料的大深径比微小深孔加工。     

Influence of electrical discharge machining parameters on cutting parameters of carbon fiber-reinforced plastic

Today the use of high-strength carbon fiber-reinforced plastics (CFRP) composite as a material for many engineering applications is showing an increasing demand in the industry. These composites are replacing the traditional use of steel because they offer many advantages such as very light weight, high strength, and high stiffness associated with good corrosion-resistant properties. Unfortunately, there is little technological knowledge on the electrical discharge machining (EDM) process of high-strength composite materials, especially about the CFRP. In this work, a study has made into the possibility of using EDM process as a means of machining CFRP composite. Various cutting conditions such as peak current, pulse-on time, pulse-off time and open-circuit voltage were selected to perform electrical discharge machining. The effect of electrode rotation was also studied. Optimum cutting conditions and machine settings for EDM were chosen for machining CFRP composites.     

Experimental research on effects of process parameters on servo scanning 3D micro electrical discharge machining

Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials.In 3D SSMEDM process,the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap,instead of the traditional methods that depend on experiential models or intermittent compensation.However,the effects of process parameters on 3D SSMEDM have not been reported up until now.In this study,the emphasis is laid on the effects of pulse duration,peak current,machining polarity,track style,track overlap,and scanning velocity on the 3D SSMEDM performances of machining efficiency,processing status,and surface accuracy.A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon.The experimental results were obtained as follows.Peak current plays a main role in machining efficiency and surface accuracy.Pulse duration affects obviously the stability of discharge state.The material removal rate of cathode processing is about 3/5 of that of anode processing.Compared with direction-parallel path,contour-parallel path is better in counteracting the lateral wear of tool electrode end.Scanning velocity should be selected moderately to avoid electric arc and short.Track overlap should be slightly less than the radius of tool electrode.In addition,a typical 3D micro structure of eye shape was machined based on the optimized process parameters.These results are beneficial to improve machining stability,accuracy,and efficiency in 3D SSMEDM.     

Optimisation of the electrical discharge machining process using a GA-based neural network

In this paper, the optimisation of the EDM process parameters from the rough cutting stage to the finish cutting stage has been reported. A trained neural network was used to establish the relationship between the process parameters and machining performance. Genetic algorithms with properly defined objective functions were then adapted to the neural network to determine the optimal process parameters. Examples with specifications intentionally assigned the same values as those recorded in the database or selected arbitrarily have been fed into the developed GA-based neural network in order to verify the optimisation ability throughout the machining process. Accordingly, the optimised results indicate that the GA-based neural network can be successfully used to generate optimal process parameters from the rough cutting stage to the finish cutting stage.     

Modelling of surface finish,electrode wear and material removal rate in electrical discharge machining of hard-to-machine alloys

Hard-to-machine alloys are commonly used for industrial applications in the aeronautical, nuclear and automotive sectors, where the materials must have excellent resistance to corrosion and oxidation, high temperature resistance and high mechanical strength. In this present study the influence of different parameters of the electrical discharge machining process on surface roughness, electrode wear and material removal rate have been studied. Regression techniques are employed to model arithmetic mean deviation Ra (μm), peak count Pc (1/cm), material removal rate MRR (mm³/min) and electrode wear EW (%). All these parameters have been studied in terms of current intensity supplied by the generator of the electrical discharge machine I (A), pulse time t_i (μs), duty cycle η and open-circuit voltage U (V). This modelling allows us to obtain mathematical data and models to predict that the most influential factor in MRR and Ra is the current intensity and in the case of EW and Pc is the pulse time.     

Three-dimensional shaping by dot-matrix electrical discharge machining

This paper deals with a new prototyping method called dot-matrix electrical discharge machining (EDM) with scanning motion. The machining process by the dot-matrix method is similar to printing motion with a dot-impact printer. This method can be applied not only to EDM but also electrochemical machining and forming. A prototype of the machining unit for the dot-matrix method has six feeding devices for thin wire electrodes. The electrodes of 300 μm in diameter are arranged with the pitches of 760 μm. To obtain a smooth surface, a planetary motion in the x-y-plane is added to the feeding of the machining unit in the z-direction, the same area is machined repeatedly, or the machining unit is moved with fine feed. By compensating for the wear of the electrode during the scanning EDM, various shapes with the accuracy of micrometers order can be obtained without a formed tool electrode.     

A review on the use of dielectric fluids and their effects in electrical discharge machining characteristics

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. In electrical discharge machining (EDM), a process utilizing the removal phenomenon of electrical discharge in dielectric, the working fluid plays an important role affecting the material removal rate and the properties of the machined surface. Choosing the right dielectric fluid is critical for successful operations. This paper presents a literature survey on the use of dielectric fluids and also their effects in electrical discharge machining characteristics.     

Electrical discharge machining of submicron holes using ultrasmall-diameter electrodes

We have carried out the electrical discharge machining (EDM) of submicron holes using ultrasmall-diameter electrodes. Two types of electrode were used: tungsten electrodes fabricated by the combination of wire electrodischarge grinding and electrochemical machining, and silicon electrodes originally designed as probes for scanning probe microscopes. The diameters of the former and latter were 1 μm or less, and less than 0.15 μm, respectively. Holes were drilled using a relaxation-type pulse generator at an open-circuit voltage of less than or equal to 20 V with the machine's stray capacitance as the only capacitance. Using tungsten electrodes, holes of less than 1 μm in diameter and more than 1 μm in depth were successfully drilled. A 1.3-μm-wide slot was also fabricated by drilling many holes with a small pitch. It was possible to drill holes of approximately 0.5 μm diameter using silicon electrodes because the electrode diameter was less than those of the tungsten electrodes. These holes have the smallest reported diameter for holes drilled by EDM, indicating the possibility of submicron- and nanoscale machining by EDM.