Design of ECM tool electrode with controlled conductive area ratio for holes with complex internal features

The design method of electrochemical machining (ECM) tool electrode with controlled conductive area for the machining of holes with given complex internal features was presented in this paper. Such holes were difficult to machine with traditional mechanical machining methods. In authors’ previous work, it has been proved that electrochemical machining (ECM) using tool electrode with controlled conductive area ratio was effective to machine many kinds of complex holes. However, it is considered that the inverse problem, i.e., designing of suitable tool electrode for given internal feature is of great importance for practical application. Therefore, in this work, the proposed ECM process was modeled to investigate the electric potential and current distribution in the electrolyte and on the electrodes’ surface, and the evolution of inner hole profile. Then, the relationship between conductive area ratio and the machining depth was investigated by a set of fundamental simulation experiments. Simulation result showed that suitable tool electrode with specific helical conductive area can be designed for the machining of hole with given internal feature. A prototype tool electrode with non-uniform conductive area ratio from its tip to the root was fabricated and used in the verification experiment. The machining result showed that a free-formed hole was successfully shaped and the inner hole profile is in well accordance with the given internal feature.     

Proposal of ECM method for holes with complex internal features by controlling conductive area ratio along tool electrode

Holes with complex internal features are difficult to machine with traditional mechanical machining methods. In this paper, a novel electrochemical machining (ECM) method using a tool electrode with controlled conductive area ratio to shape the complex inner surface of the hole was presented. The machining process was modeled to investigate the electric potential and current density distribution on the electrodes’ surface and in the electrolyte, and the evolution of the shape of inner surface of the hole. Simulation results showed that the proposed ECM method has the potential to create holes with various complex internal features. A prototype tool electrode with gradually decreased conductive area from its tip to the root was fabricated and used in the verification experiment. The machining result showed that a reverse-tapered hole was successfully shaped and the inner hole profile is in well accordance with the simulation result.     

Electrochemical machining of the spiral internal turbulator

Electrochemical machining (ECM) is promising to machine the complex surface due to the advantages of no tool wear, stress free, and good machining accuracy. In this study, a machining method of the spiral internal ribs by ECM is presented. Firstly, the ECM experimental system is developed, which consists of electrolyte supply module, power supply unit, and workpiece-holding device. Then, a shaped cathode was used to process the spiral-turbulated hole on the built system. The shaped cathode was prepared by means of ultraviolet-curing mask method considering the expected spiral turbulator’s shape. Furthermore, parameters affecting the machining accuracy in shape duplication and machining efficiency are analyzed and discussed, especially the voltage and electrolyte concentration which have the main effect on the processed results.     

磨粒辅助EDM与ECM复合加工技术

微机电系统(Micro electromechanical systems,MEMS)的快速发展与产品微型化的发展趋势对微细结构表面(包括微孔、微槽和微棱柱/锥等)的加工质量提出了更高的要求,为了提高微细结构表面的加工质量,提出一种磨粒辅助放电加工(Electrodischarge machining,EDM)与电化学加工(Electro chemical machining,ECM)复合加工新方法,通过建立微加工模型分析了该方法的加工机理,搭建了微加工试验平台,并进行了工艺参数优化研究,采用直径500μm和75μm的钨电极在SUS 304不锈钢上分别进行了微盲孔和微通孔加工试验研究,结果表明,在所用的EDM、EDM与ECM复合加工和磨粒辅助EDM与ECM复合加工三种方法中,磨粒辅助EDM与ECM复合加工方法获得的表面粗糙度(Ra15 nm)最高,因此该方法是微细结构表面高效和高质量加工的最佳方法之一。     

不同流场构型对微细螺旋孔电解加工的影响

为了研究微细螺旋孔电解加工中不同流场构型对加工效果的影响,首先介绍了一种微细螺旋孔电解加工（ECM）用工具电极的制作工艺方法;然后,通过改变电极绝缘层厚度构造不同的螺旋孔电解加工流场构型,并对其进行了数值分析;最后,通过电解加工实验对分析结果进行了验证。研究结果表明,在其它条件不变的情况下,涂层厚度越厚,加工效果越好。     

A simplified mathematical model development for the design of free-form cathode surface in electrochemical machining

High-performance machining of free-form surfaces is highly critical in automotive, aerospace, and die–mold manufacturing industries. Therefore, electrochemical machining (ECM) process has been used in such cases in that sense. The most important challenges of using ECM process are the lack of accuracy and difficulty in designing proper machining tool (cathode) surfaces. In this article, a simplified mathematical model is presented to obtain a cathode surface for ECM of free-form surfaces which have high curvatures. In this theoretical approach, the finite-element method (FEM) is used to solve the 3-D Laplace equation and to determine the potential distribution between the anode (workpiece) and cathode (tool) surfaces. A compact and simple program was developed to obtain a proper cathode surface that only requires some nodal coordinates on the anode surface and boundary conditions. In this work, a trial cathode surface is constructed for a given gap distance. For the determined ECM parameters, cathode shape that satisfies the boundary conditions is obtained for the 45^th layer. The results are compared with the literature and ANSYS Workbench for verification. The developed theoretical approach benefits simpler and faster FEM solutions, accurate cathode surface, and consequently correct form of machined surface.     

基于电场分析的钛合金电解加工圆孔成形研究

以钛合金电解加工圆孔为对象,充分考虑加工中电场与移动网格相互关系建立了圆孔加工理论模型,采用数值计算方法得到了电解加工圆孔电位分布、电流密度分布、成形过程和材料变化,探讨了不同加工参数（脉冲平均电压、电导率和进给速度）对电解加工圆孔成形的影响,并开展了电解加工圆孔实验,得到了圆孔形貌,在相同加工参数下,理论计算和实验得到的圆孔深度分别1.07mm和1.157 14mm,两者能够较好地吻合,可为电解加工圆孔提供理论依据。     

Development of multi-objective optimization models for electrochemical machining process

Owing to the complexity of electrochemical machining (ECM), it is very difficult to determine optimal cutting parameters for improving cutting performance. Hence, optimization of operating parameters is an important step in machining, particularly for unconventional machining procedures like ECM. A suitable selection of machining parameters for the ECM process relies heavily on the operator’s technologies and experience because of their numerous and diverse range. Machining parameters provided by the machine tool builder cannot meet the operator’s requirements. Since for an arbitrary desired machining time for a particular job, they do not provide the optimal conditions. To solve this task, multiple regression model and ANN model are developed as efficient approaches to determine the optimal machining parameters in ECM. In this paper, current, voltage, flow rate and gap are considered as machining parameters and metal removal rate and surface roughness are the objectives. Then by applying grey relational analysis, we calculate the grey grade for representing multi-objective model. Multiple regression model and ANN model have been developed to map the relationship between process parameters and objectives in terms of grade. The experimental data are divided into training and testing data. The predicted grade is found and then the percentage deviation between the experimental grade and predicted grade is calculated for each model. The average percentage deviations for the training data of the linear regression model, logarithmic transformation model, excluding interaction terms and ANN model, are 12.7, 25.6 and 3.03, respectively. The average percentage deviations for the testing data of the three models are 9.83, 26.8 and 2.67. While examining the average percentage deviations of three models, ANN is having less percentage deviation. So ANN is considered as the best prediction model. Based on the testing results of the artificial neural network, the operating parameters are optimized. Finally, ANOVA is used to identify the significance of multiple regression model and ANN model.     

高精度镗刀微调机构

在镗床上加工或修理高精度内孔时,普遍存在刀具调整难、效率低、加工精度难以保证的问题。提出了一种高精度镗刀微调机构,该机构利用大传动比轮系传动,通过微调镗刀的径向移动量,其孔径加工精度可达1μm以下。     

高速高精度扩孔的NC刀具轨迹设计

文章提出了螺旋扎孔加工方法,根据有元预制孔、是否为通孔等情况,设计了NC刀具的加工轨迹,提高了孔的精度与效率。     

基于模糊神经网络的深孔加工刀具磨损率预测

刀具的过快磨损不仅增大加工成本,也影响工件的最终加工质量,因此预测和减少刀具磨损率具有重要意义。由于BP神经网络本身容易陷入局部极小值、收敛速度慢等缺陷,且深孔加工过程及其复杂,无法建立加工中刀具磨损率与加工参数之间的准确数学模型,故采用模糊神经网络建立BTA刀具磨损率在线钻削模型。仿真和实验结果表明,该模型能有效预测BTA刀具磨损率,对提高刀具寿命和加工深孔的质量具有一定的意义。     

高精度硬质合金套类零件的加工方法

介绍硬质合金套类零件电解和电解磨削加工的基本原理,综合运用了以下多种新工艺:螺旋电极电解扩孔、螺旋 电极电解磨孔、中极法电解磨削外圆及端面。     

A study on micro machining of e-glass–fibre–epoxy composite by ECSM process

The paper presents the result of an experimental investigation on the micro machining of electrically non-conductive e-glass–fibre–epoxy composite during electrochemical spark machining using specially designed square cross section with centrally micro hole brass tool and different diameter round-shaped micro tools made of IS-3748 steel. A micro electrochemical spark machining (ECSM) setup has been designed, fabricated and used for conducting the experiments. According to the Taguchi method-based design, the specific numbers of experiments have been carried out to investigate the influence of the fabricated ECSM parameters on the material removal rate and overcut on generated hole radius. Test results show that the material removal rate is maximum when machining was performed at higher setting value of D.C. supply voltage (e.g. 70?V), moderate setting value of electrolytic concentration (e.g. 80?g/l) and 180-mm gap between electrodes. Taking significant machining parameters into consideration and using multiple linear regression, mathematical modes for material removal rate and overcut on hole radius are established to investigate the influence of cutting parameters during micro-ECSM. The influence of machining parameters on machined hole and special shape contour quality are also analysed through different scanning electron micrographs. Confirmation test results established the fact that the developed mathematical models are appropriate for effectively representing the machining performance criteria.     

电解加工的间隙监测与控制

加工间隙的监测与控制是电解加工的一个重要研究内容。本文提出了循环迭代间隙控制方案,根据前次循环中加工状况,对进给速度、进给量进行相应调整。在自行研制的立式电解加工机床上,采用虚拟仪器技术构建了电解加工控制系统。研究了有电解液存在情况下进行对刀(湿对刀)的问题。试验结果表明,在电解液中可以实现精确对刀;循环迭代间隙控制可以快速调整工具进给速度,使之近似等于工件去除速度,从而精确地维持恒定的小间隙。     

An investigation of bell mouthing in precision hole machining with self-piloting tools

The bell mouth is the tapered hole entrance and it is unavoidable disadvantage of the machining with self-piloting tools. A comprehensive theoretical and experimental study of bell mounting in precision hole machining with self-piloting tools is carried out. The prime concern of the theoretical part is the mechanism of the bell mouth formation. The main factors affecting bell mouth have been revealed by analyzing mechanics of tool entrancing into the workpiece. Three working methods with self-piloting tools are considered and the recommendations made relevant to the tool and machine tool design. Experimental part of the study involved Boring and Trepanning Association self-piloting drilling on special designed deep-hole drilling machine. The main objective of this part was to obtain the quantitative relationships between the bell mouth parameters and the cutting regime. The technique of the statistical design of experiments along with a special procedure for the data acquisition and analysis provided to cover the whole range of the process parameters and to get the mathematical model accounted the parameters interaction.     

改进精密镗床加工精度的方法应用

针对高精度孔在镗削加工中出现的孔表面质量不稳定和孔的圆柱度波动大的实际问题,通过对镗杆和机床丝杠的改进,使镗床的加工精度及其所加工内孔的重要指标精度均有了显著提高.     

How microtool dimension influences electrochemical micromachining

Recent innovations in the area of electrochemical micromachining (μECM) have created a unique opportunity for fabricating microproducts in the micron scale. A significant constraint in attaining improved machining effectiveness in μECM applications is that of achieving the correct microtool geometry for a specified workpiece profile. This study focuses on the influences of microtool dimension on machining characteristics of electrochemical microdrilling on nickel plate. During microtool fabrication, tungsten microshafts are electrochemically etched to make desired cylindrical microtools of different lengths and diameters to investigate the effects of tool dimension on electrochemical micromachining. The shape and size of the fabricated microholes, material removal rate, machining time, and taper angle formed in the fabricated microholes are considered as response factors. After machining, the shape and size of microdrilled holes are measured and compared to tool geometry. From the experiment, it is found that the material removal rate, machining time, and the size of fabricated microhole are significantly influenced by the microtool dimension.     

BLOCK EDG: ISSUES AND APPLICABILITY IN MULTIPLE PASS µED-MILLING

Fabrication of micro-features by a Micro ED-milling (μED-milling) process requires machining of tool electrode and applying them in multi-pass trajectory. A real concern occurs when the tool has to be prepared before each pass and put into trajectory without disturbing the settings. This issue is attested to here by combining the process setup ofμED-milling, and Block Electric Discharge Grinding (Block EDG) without hindering the functionality of individual processes. But the Block EDG process itself suffers with a primary setback such as inability to predict the change in tool diameter during machining. The ability of Block EDG process is improved in this work by formulating regression model and tool quality loss characteristics evaluation. An empirical model for tool diameter as a function of energy and machining time is developed and validated to predict the diameter online at any point of machining. A data chart is prepared to show the typicalμ-tool defects during the fabrication process and possible remedies. Finally, the article concludes with employing the fabricated tools inμED-milling process to produce complex shapes through multiple pass machining technique.     

Recent developments and research challenges in electrochemical micromachining (µECM)

Electrochemical machining (ECM) and especially electrochemical micromachining (μECM) became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro-applications such as microfluidics systems and stress free drilled holes in automotive and aerospace manufacturing with complex shapes. Electrochemical machining is a non-conventional machining process based on the phenomenon of electrolysis. This process requires maintaining a small gap (size of a few μm)—the inter-electrode gap—between the anode (workpiece) and the cathode (tool electrode) in order to achieve acceptable machining results (i.e. accuracy, high aspect ratio with appropriate material removal rate and efficiency). This paper presents different problematic areas of electrochemical micromachining (often referred to as electrochemical micromachining or μECM). The aim of this paper is to address the problems met by the μECM technology developers and to present the current state-of-the-art solutions.     

基于ProE三维造型技术求解空间斜面或空间斜孔的加工问题

加工空间斜孔历来是机械加工中的难题之一。对组合机床设计中常见的空间斜面或空间斜孔的加工问题进行了分析,利用ProE三维造型技术,通过空间剖切方法,求解被加工零件的空间斜面或空间斜孔的角度关系,任何一种空间斜面或者空间斜孔的方向矢量,总可以通过最多3次旋转,使其对准加工主轴,使用该方法机床夹具的设计将能够简化。以摩托车发动机壳体的加工实例来说明该方法使用过程,结果表明所设计的夹具,完全满足精度要求,本实例具有普遍的推广性和实用性。