Experimental investigation of burr reduction during EDM end-milling hybrid process

Burrs are always generated during the end-milling process of ductile materials and have become a common challenge because a large plastic flow of the material is generated during cutting. In this research, a combination method of the end-milling and electrical discharged machining (EDM) process is proposed to suppress the generated burrs during machining; this process is called the EDM end-milling process. EDM end-milling was performed for side milling of AISI 1045 alloy steel (HRC = 28). The height of the generated burrs was measured and compared between ordinary end milling and EDM end-milling, and the experimental results indicate that the generated burrs are suppressed effectively by EDM end-milling owing to the effect of reduced plastic flow. The experimental results also indicate that the height of the generated burrs decreases when the capacitance values are increased during EDM end-milling. Furthermore, the results show that the height of the generated burrs remains unchanged by EDM end-milling when the axial depth of cut is increased.

     

硬质合金电火花加工性能的试验研究

通过试验研究硬质合金的电火花加工中脉冲宽度、峰值电流等电参数对加工速度、电极损耗、加工表面粗糙度的影响规律,得出结论:脉冲宽度和峰值电流必须在一个合适的范围内才能得到较好的加工效果。     

Experimental analysis of boring process on automotive engine cylinders

In this article, mechanics of boring process on cast iron automotive engine cylinders is explored experimentally. In order to shorten the boring cycle time and to improve quality of the cylinder holes, effects of various cutting conditions as spindle speed, feedrate, inserts, and coatings are investigated. Real-time cutting forces are measured with dynamometer during the process. Surface roughness on the engine cylinders, flank, and crater tool wears are measured and compared in various cutting conditions. It is concluded that by selecting proper cutting conditions, cutting forces can be controlled below a threshold value, cycle time can be shortened, tool life and part quality can be increased; therefore, the cost of automotive engine boring process can be reduced significantly.     

Experimental investigation and prediction of optimum process parameters of micro-wire-cut EDM of 2205 DSS

Micro-wire-cut electrode discharge machining (EDM) is an emerging manufacturing process in the field of micro-manufacturing to fabricate the complex profiles of micro-components. It is a complex process involving various process parameters such as pulse on time, pulse off time, wire speed, wire tension and current. In addition to micro-fabrication, this process can also be extended in the field of tool design and developments such as dies, moulds, precision manufacturing, contour cutting, etc., where complex shapes need to be generated with high-grade dimensional accuracy and surface finish. In this research work, an attempt is made to investigate the effect of process parameters on the output variables such as material removal rate (MRR), surface finish and the cutting width (kerf) of wire-cut EDM for duplex stainless steel (DSS). Scanning electron microscopy (SEM) has been used to capture the images of the kerf width, and the measurements are taken with the help of the welding expert system and software. An optimization technique (Taguchi method) has been employed to identify the optimum parameters of the micro-wire-cut EDM process for cutting 2205 grade duplex stainless steel. The effect of each control parameter on the performance measure is studied individually using the plots of signal to noise ratio.     

Fabrication of micro-end mill tool by EDM and its performance evaluation

Abstract

Micro-milling is a fast, cheap and controlled process compared to other micro-fabrication processes such as lithography, laser/electron/ion beam machining, etc. However, scarcity of cutting tools of very small dimensions often results in limited application of micro-milling. In the present study, electro discharge machining (EDM) is used for fabrication of micro-end mill tool. To ensure high dimensional accuracy of the tool, a parametric study is conducted by replicating the a tungsten carbide block to a tungsten carbide (WC) block. The relationships between the drilled cavities on the block and the features on the micro-tool are established. The influence of machining parameters (voltage, capacitance and spindle speed) on the response variables (entrance diameter, hole depth, material removal rate (MRR) and surface roughness) is reported. Capacitance is found more dominant as compared to other selected process parameters. Using optimized parameters from the parametric study, a WC micro-end mill tool of 100?µm diameter is fabricated. Channel of around 110 µm width, 40?µm depth and surface roughness of 70?nm is successfully fabricated on aluminum. The performance of the fabricated tool is compared with a commercial end mill tool by milling micro channels on stainless steel.     

Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology

In this study, thermal modeling and finite element simulation of electrical discharge machining (EDM) has been done, taking into account several important aspects such as temperature-dependent material properties, shape and size of the heated zone (Gaussian heat distribution), energy distribution factor, plasma flushing efficiency, and phase change to predict thermal behavior and material removal mechanism in EDM process. Temperature distribution on the cathode has been calculated using ANSYS finite element code, and the effect of EDM parameters on heat distribution along the radius and depth of the workpiece has been obtained. Temperature profiles have been used to calculate theoretical material removal rate (MRR) from the cathode. Theoretically calculated MRRs are compared with the experimental results, making it possible to precisely determine the portion of energy that enters the cathode for AISI H13 tool steel. Also in this paper, the effect of EDM parameters on MRR has been investigated by using the technique of design of experiments and response surface methodology. Finally, a quadratic polynomial regression model has been proposed for MRR, and the accuracy of this model has been checked by means of analysis of residuals.     

电火花小孔加工速度的工艺试验研究

简述电火花小孔加工试验原理及系统构成,并分析了工件材料的热物理系数、平均功率及脉冲宽度等参数对电火花小孔加工速度的影响,为实际应用提供了重要参考。     

Identification of dynamic properties of boring bar vibrations in a continuous boring operation

Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler–Bernoulli beam model.     

Experimental investigation on various tool path strategies influencing surface quality and form accuracy of CNC milled complex freeform surface

Four tool path strategies such as equal-interval tool paths, parallel tool paths, parallel–tangency tool paths, and freeform tool paths are proposed in computer numerical control milling of a complex freeform surface. The objective is to understand how 3D tool paths influence their machining efficiency, surface quality, and form accuracy. In this study, their scallop heights were less than or equal to 15 μm. First, their scallop heights distributions and 3D tool path distances were theoretically analyzed; then, four tool path strategies were investigated with reference to machining efficiency, surface texture height, surface roughness, and form errors. It is shown that scallop heights distribution can be used to display the surface texture state and predict tool path distance. Experimental results indicate that the surface texture height, the surface roughness, and the form errors were nearly identical on the machined flat location and surface for various tool path strategies, whereas their surface quality and form accuracy are easily destroyed on the abrupt ones except for the parallel tool paths. Although the freeform tool paths produce the shortest tool path distance through 3-axes driving mode, the parallel tool paths offer the best surface quality and form accuracy through 2-axes driving mode. This is because the 3-axes driving and its vector changes on abrupt location easily lead to large machine vibration and movement errors. It is confirmed that the parallel tool path strategy with 2-axes driving mode can improve the surface quality and form accuracy in actual milling of a complex freeform surface.     

Influence of magnetorheological elastomer on tool vibration and cutting performance during boring of hardened AISI4340 steel

During boring process, tool vibration is a major concern due to its overhanging length, which results in high cutting force, poor surface finish, and increase in tool wear. To suppress tool vibration and improve cutting performance, a novel technique in rheological fluid was designed and developed. In this work, a magnetorheological elastomer (MRE) was developed, and parameters, such as piston location, current intensity, and coil winding direction, were considered. Cutting experiments were conducted to obtain a set of parameters that can efficiently control vibration during boring of hardened AISI 4340 steel. Taguchi method was used to optimize the cutting condition, and findings show that the cutting tool embedded with the MRE reduced tool vibration and effectively increased cutting performance.

     

一种新型深孔镗刀研制

深孔镗削是深孔加工的重要部分,对其展开研究具有重要意义.以无氧铜难加工材料深孔镗刀研制试验为主要研究对象.分析深孔镗削运动形式、深孔镗削受力、深孔镗刀设计基本理论;设计并加工无氧铜材料的深孔镗刀,并进行相关刀具切削加工试验.分析加工试验中出现问题,提出解决问题的方法,通过试验来证明该方法的可行性,指导并应用于深孔加工的生产实际中.为以后实现相应材料和形状的零件的加工提高宝贵的经验,对深孔镗刀进一步研究具有很高的经济和研究价值.     

Optimization of EDM process for multiple performance characteristics using Taguchi method and Grey relational analysis

Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal processes. The Taguchi method has been utilized to determine the optimal EDM conditions in several industrial fields. The method, however, was designed to optimize only a single performance characteristic. To remove that limitation, the Grey relational analysis theory has been used to resolve the complicated interrelationships among the multiple performance characteristics. In the present study, we attempted to find the optimal machining conditions under which the micro-hole can be formed to a minimum diameter and a maximum aspect ratio. The Taguchi method was used to determine the relations between machining parameters and process characteristics. It was found that electrode wear and the entrance and exit clearances had a significant effect on the diameter of the micro-hole when the diameter of the electrode was identical. Grey relational analysis was used to determine the optimal machining parameters, among which the input voltage and the capacitance were found to be the most significant. The obtained optimal machining conditions were an input voltage of 60V, a capacitance of 680pF, a resistance of 500Ω, the feed rate of 1.5μm/s and a spindle speed of 1500rpm. Under these conditions, a micro-hole of 40μm average diameter and 10 aspect ratio could be machined.     

T68卧式镗床镗轴轴向窜动的故障分析与改造

T68卧式镗床镗轴轴向窜动产生于镗轴运转时的传动链各配合件的配合间隙。该配合间隙随着传动磨合时间的增加而增大,当超过设计制造允许值时将导致镗轴轴向窜动故障,使镗轴在铣削工件平面时平面度超差。具有明显故障特征的配合件有轴承与丝杠、滑座螺母与丝杠、滑座螺母内外组合体、传动啮合齿轮等。通过改造镗轴滑座螺母与丝杠不能自锁的锁紧机构装置,控制滑座位移,即在滑座导轨压板上加装压板,用螺钉紧固,将滑座与尾部箱体连成一体,故障排除,彻底解决了镗轴铣削工件平面平面度超差的问题。     

Experimental investigation of tool vibration and surface roughness in the precision end-milling process using the singular spectrum analysis

The vibrations on the cutting tool have a momentous influence for the surface quality of workpiece with respect to surface profile and roughness during the precision end-milling process. Singular spectrum analysis (SSA) is a new non-parametric technique of time series analysis and forecasting. The significant features of the cutting tool vibration signals from the sensors are extracted and transformed from the SSA-processed vibration signals. In the present study, SSA is applied to extract and transform the raw signals of the vibrations on the cutting tool for investigating the relationship between tool vibration and surface roughness in the precision end-milling process of hardened steel SCM440. In this experimental investigation, the spindle speed, feed rate, and cutting depth were chosen as the numerical factor; the cutting feed direction and holder type were regarded as the categorical factor. An experimental plan consisting of five-factor (three numerical plus two categorical) d-optimal design based on the response surface methodology was employed to carry out the experimental study. A micro-cutting test was conducted to visualize the effect of vibration of tooltip on the performance of surface roughness. With the experimental values up to 95% confidence interval, it is fairly well for the experimental results to present the mathematical models of the tool vibration and surface roughness. Results show that the effects of feed rate and cutting depth provide the reinforcement on the overall vibration to cause the unstable cutting process and exhibit the result of the worst machined surface. The amplitude of vibration signals along the cutting feed direction is generally larger than that along other direction. The spindle speed and tool holder type affect the stability of cutting tooltip during the cutting process.     

Development of an intelligent process model for EDM

This paper reports the development of an intelligent model for the electric discharge machining (EDM) process using finite-element method (FEM) and artificial neural network (ANN). A two-dimensional axisymmetric thermal (FEM) model of single-spark EDM process has been developed based on more realistic assumptions such as Gaussian distribution of heat flux, time- and energy-dependent spark radius, etc. to predict the shape of crater cavity, material removal rate, and tool wear rate. The model is validated using the reported analytical and experimental results. A neural-network-based process model is proposed to establish relation between input process conditions (discharge power, spark on time, and duty factor) and the process responses (crater geometry, material removal rate, and tool wear rate) for various work—tool work materials. The ANN model was trained, tested, and tuned using the data generated from the numerical (FEM) simulations. The ANN model was found to accurately predict EDM process responses for chosen process conditions. It can be used for the selection of optimum process conditions for EDM process.     

金刚石工具头超声波复合加工的实验研究

研究了金刚石工具头超声波复合加工方法的可行性及加工参数与材料去除率的关系。在研究超声加工，超声复合加工和金刚石工具的基础上，借助SEM分析其典型塑性材料和脆性材料的加工形貌，初步讨论了该方法去除材料的机理。     

Study of the EDM performance to produce a stable process and surface modification

In this work, the effect of pulse current and pulse duration in die-sinking electrical discharge machining (EDM) on the machining characteristics of Ti-6Al-4V alloy is studied. The EDM characteristics, including the electrode wear ratio (EWR), the material removal rate (MRR), and the surface roughness (SR), are used to measure the effect of machining. An increase in the intensity of the pulse current from 2.5 to 5 A produces a slow increase in EWR, MRR, and SR. An increase in the intensity of the pulse current from 5 to 7 A produces a rapid increase in EWR, MRR, and SR. Control charts are basic and powerful tools for controlling statistical processes and are widely used to monitor manufacturing processes and ensure good EDM quality. EWR, MRR, and SR are normal distributions, and the regression curves for the data are straight lines. All of the data points vary randomly around the centerline, which follows the Shewhart criteria and shows that the EDM process and product performance are under control and stable over time. After EDM, the surface exhibits an irregular fused structure, with pinholes, micro voids, globule debris, and many damaged surfaces. Oxygen plasma etching and surface modification after EDM reduce these surface defects, so finer and flatter surfaces can be achieved. Moreover, fatigue life can be enhanced.     

Experimental and numerical true strain assessment on sheet forming for different tool design

The forming tests are being developed with the purpose of enabling forming companies to better understand the sheets formability. The identification of the regions where tension-tension, tension-compression, and/or plane strain occurred during the forming process can aid the process planning through the tools geometry optimization. This work consisted of evaluating, experimental and numerically, the major true strain obtained with different punch designs, which were used in addition to the traditional Nakazima test tool. The main objective was to study the true strain profile as an alternative method to analyze the tool design influence on stretching forming of high stampability steels (DC 06). The friction coefficient was investigated, and an evaluation was also made of the chosen program's response quality (validation). The results are given as a major true strain distribution profile at points distributed linearly from the region close to the die radius to the punch pole. The result expectation is to help the process planning and the material evaluation based on the correct tool design specification in order to obtain the desired true strain distribution in the formed part.