Wire Electrical Discharge Grinding Research Articles

Development of Micro Electrical Discharge Machine and Micro-hole Machining Using Multiple Micro Electrodes

Recent advances in microtechnology have highlighted the need for fabricating microscopic parts with complex three-dimensional structures. This, in turn, has increased the demand for innovative tools. Micro electrical discharge machining (MEDM) is one such technique that has proven to be effective in producing parts that are difficult to fabricate using traditional manufacturing methods, such as micro shafts and micro holes. Therefore, this study focuses on the development of a specialized MEDM system that incorporates an optimized wire electrical discharge grinding (WEDG) module. Additionally, the study successfully fabricates microelectrodes for use as cutting tools using the MEDM/WEDG system. These micro-electrodes are then utilized in the precise fabrication of various types of multiple micro electrodes through the use of reverse electrical discharge machining (REDM). These multiple micro electrodes are subsequently employed in precise hole machining operations using MEDM. The application of REDM signifies a significant technological advancement in the precision fabrication of microstructures. Furthermore, it is expected to greatly enhance the versatility and efficiency of microtechnology manufacturing processes. Overall, REDM represents a new approach to manufacturing that is capable of producing more complex and high-precision microstructures.

Editors' Choice—Improving Quality of EDMed Micro-Holes on Titanium via In Situ Electrochemical Post-processing: A Transient Simulation and Experimental Study

Electrical discharge micromachining (EDM) poses challenges to the fatigue-life performance of machined surfaces due to thermal damage, including recast layers, heat-affected zones, residual stress, micro-cracks, and pores. Existing literature proposes various ex situ post-processing techniques to mitigate these effects, albeit requiring separate facilities, leading to increased time and costs. This research involves an in situ sequential electrochemical post-processing (ECPP) technique to enhance the quality of EDMed micro-holes on titanium. The study develops an understanding of the evolution of overcutting during ECPP, conducting unique experiments that involve adjusting the initial radial interelectrode gap (utilizing in situ wire-electrical discharge grinding) and applied voltage. Additionally, an experimentally validated transient finite element method (FEM) model is developed, incorporating the passive film formation phenomenon for improved accuracy. Compared to EDM alone, the sequential EDM-ECPP approach produced micro-holes with superior surface integrity and form accuracy, completely eliminating thermal damage. Notably, surface roughness (Sa) was reduced by 80% after the ECPP. Increasing the voltage from 8 to 16 V or decreasing the gap from 60 to 20 μm rendered a larger overcut. This research’s novelty lies in using a two-phase dielectric (water-air), effectively addressing dielectric and electrolyte cross-contamination issues, rendering it suitable for commercial applications.

Research on Geometric Constraint Strategies for Controlling the Diameter of Micro-Shafts Manufactured via Wire Electric Discharge Grinding.

Micro-tools comprising difficult-to-machine materials have seen widespread application in micro-manufacturing to satisfy the demands of micro-part processing and micro-device development. Taking micro-shafts as an example, the related developmental technology, based on wire electric discharge grinding (WEDG) as the core method, is one of the key technologies used to prepare high-precision micro-shafts. To enable efficient and high-precision machining of micro-shafts with target diameters, instead of performing multiple repeated on-machine measurements and reprocessing, a geometric constraint strategy is proposed based on the previously introduced twin-mirroring-wire tangential feed electrical discharge grinding (TMTF-WEDG). This strategy encompasses the tool setting method, tangential feed distance compensation, and an equation that establishes the relationship between tangential distance and diameter variation. These components are derived from a key points analysis of the geometric constraints. The micro-shafts with diameters of 50 µm and consistencies of ±1.5 µm are repeatedly processed. A series of micro-shafts with diameters ranging from 30 µm to 120 µm achieve geometric constraints with a diameter accuracy of ±2 µm, accompanied by the complete continuous automation of the entire process. Accordingly, it can be concluded that the geometric constraint strategy is flexible and stable and can be controlled with high precision in the TMTF-WEDG process.

Experimental Investigation of the Effects of Machining Parameters on the Performance of Form-Cutting Tools Manufactured by Wire Electrical Discharge Machining (WEDM) and Grinding Processes.

In this research, a comparison between two methods of grinding and WEDM and the chip formation of each form tool was studied through a set of designs of experiments. A multi-functional form tool with different cutting-edge shapes was designed to compare different production methods, and a grinding machine and a five-axis wire-cutting machine were made. The form tools by the wire cutting method were made with three different machining states, rough, semi-finish, and finish. The results of the experimental test showed that the chip formation of the finished surface of the wire cut tool was close to the ground tools. Additionally, the tool life in wear generation was assessed, revealing that the tool generated through the wire-cutting method with three passes exhibited superior performance compared to alternative approaches. Furthermore, employing the wire-cutting technique with high surface finishing yielded optimal outcomes for producing form-cutting tools featuring complex profiles.

Experimental study on polishing of fluid magnetic abrasives for the wire electrical discharge grinding surface of micro-shafts

Experimental study on polishing of fluid magnetic abrasives for the wire electrical discharge grinding surface of micro-shafts

Influence of the punch with concave cutting-edge on the blanking force in micro punching process

Micro blanking machining is a promising manufacture technology to realize mass production of micro parts efficiently. In the process of blanking, the blanking force is significant to the punch, die, and sheet workpiece. In order to investigate the influence of cutting-edge shape of the punch on the micro blanking process, a self-developed micro combined EDM and blanking machine tool is applied in this paper. A punch with concave cutting-edge is capable to be fabricated online through a series of processing based on micro EDM: 3D milling, wire electrical discharge grinding and reverse EDM copy machining techniques. Then the punch and die are accurately matched online due to the preparation of them in the same coordinate system. Micro blanking parts and punching parts with the complex cross-sectional shape is obtained by using the online fabricated punch with flat cutting-edge and concave cutting-edge respectively in the workpiece of stainless steel SUS304 foil. The characteristic of blanking force varying with time indicates that the blanking force is significantly reduced in the case of concave cutting-edge, meanwhile, both blanking parts and punching parts have the high quality.

A study on machining performance of wire electric discharge grinding (WEDG) process during machining of tungsten alloy micro-tools

In this experimental study, tungsten alloy micro-tools of high aspect ratio are machined through wire electric discharge grinding (WEDG) method using the step machining technique on a hybrid micro-electro-discharge machine to achieve high productivity and finish. Tungsten alloy micro-tools are widely used in the fabrication of miniature products. The precise and economical machining of the tungsten material with an optimum level of accuracy and surface properties is a challenge because of its exceptional characteristics like hot hardness, high strength, low wear, and corrosion rate. The material removal rate (MRR) and surface roughness (Ra) responses are studied during machining of micro-tools, selecting the variability of applied voltage, circuit capacitance, and spindle speed during machining for a constant-aspect-ratio micro-tool. Both voltage and capacitance are found to be influencing parameters for MRR and surface roughness. Higher voltage and capacitance values tend to increase MRR and roughness values on the machined micro-tool. Further, the parametric conditions are also identified for higher MRRs and lower surface roughness (Ra) values after employing the hybrid Taguchi design of experimentation methodology. Surface topography of the machined surface studied by energy-dispersive spectroscopy (EDS) reveals the presence of pyrolytic carbon and oxygen elements. Field emission scanning electron microscopy (FESEM) images show a little waviness across the machined surface. A mathematical model is developed to evaluate the correlation among governing parameters for machining response and validated by confirmation experiments. The machining procedure can be further developed to fabricate more predominant fluted micro-tools for difficult-to-machine tungsten material.

Machining of cylindrical parts by wire electrical discharge grinding using thin plate guide

In order to meet the processing requirements of precise cylindrical parts on hard and difficult-to-machine materials, this paper introduces wire electrical discharge grinding (WEDG) using thin plate wire guide for cylindrical parts machining. The spindle system and the wire transport system to realize this processing method was added to a low speed wire electrical discharge machining (LS-WEDM) machine tool. In order to realize the online measurement of the machining accuracy of the cylindrical parts, an online measurement system of two-degree-of-freedom based on laser displacement sensor was built. The reasons for the incomplete removal of the machined surface were analyzed. Through the application of a new tool setting strategy and reasonable selection of processing parameters, the phenomenon of incomplete processing can be avoided. The experimental research on the effects of part rotational speed, wire feed rate, wire running speed and wire tension on roundness, surface roughness Sa, and surface morphology were carried out. Finally, example of the cylindrical parts is given to verify the machining accuracy.

Experimental Investigation on CO2 Laser-Assisted Micro-Grinding Characteristics of Al2O3

Fabricating micro-scale features in ceramic materials, such as alumina (Al2O3), is challenging because of their high hardness and brittleness. Laser-assisted machining, in which a laser beam is a heat source for pre-softening the local area on a workpiece, is an effective hybrid method for machining ceramics. The study identified the effects of carbon dioxide (CO2) laser-assisted micro-grinding (LAMG) with a wire electrical discharge grinding polycrystalline diamond tool on Al2O3. Comprehensive investigations have been conducted on the effects of laser beam machining itself and the effect of machining parameters, such as laser beam power, axial depth of cut, and feed rate. The average grinding force was found to decrease by 46% in the thrust direction and 44% in the feed direction, and surface roughness decreased by 17% with LAMG. Moreover, machining at a higher feed rate was possible without tool fracture. The results indicate that the CO2 laser heating of Al2O3 has significant advantages over conventional methods regarding machinability and channel geometry. Finally, an improved LAMG process to prevent edge cracks by revising the machining conditions is proposed.

Fabrication of micro rods by twin-mirroring-wire tangential feed micro electrical discharge grinding

In micro electrical discharge machining (micro-EDM), the precision fabrication of cylindrical micro rods is difficult to achieve with a high processing efficiency. In order to overcome this challenge, this paper proposes a new processing method, which is denoted as twin-mirroring-wire tangential feed micro electrical discharge grinding (TMTF-WEDG). The machining principle, characteristics, and realization of the new method are firstly introduced. Then, the advantages of TMTF-WEDG in terms of machining efficiency and accuracy are demonstrated. The experimental results have shown that the machining efficiency can be increased to more than 70% in comparison with conventional tangential-feed wire electrical discharge grinding. It has also been proved that a minimum removal of material corresponding to a reduction of less than 1 μm in the diameter of a micro rod can be obtained by TMTF-WEDG. This considerably helps in improving the accuracy and repeatability of the machining process. A deviation of less than 1 μm on the diameter of a micro rod has been obtained in a length range of 800 μm. The process repeatability in machining five micro rods has been established to be below 2 μm. The proposed method is therefore of great significance for improving the machining efficiency and ensuring a high precision in the shaping process of cylindrical micro rods.

Shaping Soft Robotic Microactuators by Wire Electrical Discharge Grinding.

Inflatable soft microactuators typically consist of an elastic material with an internal void that can be inflated to generate a deformation. A crucial feature of these actuators is the shape of ther inflatable void as it determines the bending motion. Due to fabrication limitations, low complex void geometries are the de facto standard, severely restricting attainable motions. This paper introduces wire electrical discharge grinding (WEDG) for shaping the inflatable void, increasing their complexity. This approach enables the creation of new deformation patterns and functionalities. The WEDG process is used to create various moulds to cast rubber microactuators. These microactuators are fabricated through a bonding-free micromoulding process, which is highly sensitive to the accuracy of the mould. The mould cavity (outside of the actuator) is defined by micromilling, whereas the mould insert (inner cavity of the actuator) is defined by WEDG. The deformation patterns are evaluated with a multi-segment linear bending model. The produced microactuators are also characterised and compared with respect to the morphology of the inner cavity. All microactuators have a cylindrical shape with a length of 8 mm and a diameter of 0.8 mm. Actuation tests at a maximum pressure of 50 kPa indicate that complex deformation patterns such as curling, differential bending or multi-points bending can be achieved.

Fabrication of micro rotary structures by wire electrochemical grinding

Micro rotary structures have attracted increasing attention in many industrial applications. However, the fabrication of complex micro rotary structures with high strength, high hardness, and low rigidity, poses a significant challenge to traditional machining methods. To solve this difficult problem, this study proposes a novel method of fabricating complex micro rotary structures by using wire electrochemical grinding (WECG), which is an anodic dissolution process and has no machining force. WECG, a type of ECM, has some major advantages over wire electrical discharge grinding (WEDG): no electrode wear, absence of residual stress, good surface quality, low machining cost, and high machining efficiency. Firstly, this study investigated the influences of the process parameters on the dimensional accuracy of the micro grooves produced, then optimized these process parameters. A qualitative simulation of WECG was conducted to reveal the reason for the trumpet-like micro grooves fabricated by WECG. Finally, based on the optimal process parameters, several different kinds of rotary structures were successfully produced by WECG. The experimental results demonstrate that WECG is a promising method for fabricating complex rotary structures of difficult-to-cut materials at low cost and with high efficiency.

Fabrication of tapered micro rods using twin static wire electrical discharge grinding process

Wire electrical discharge grinding (WEDG) is an attractive alternative to traditional grinding technologies for machining tapered micro rods. However, controlling the shape and diameter of the micro rods can be challenging using conventional WEDG. A new approach of WEDG using two static brass wires (TS-WEDG) is proposed in this paper for reducing the complexity in fabricating tapered micro rods. Following this approach, tapered micro rods can be fabricated by feeding a rotating micro rod along the centreline between two inclined wires. A prototype device for TS-WEDG processing has been developed. This device allows to adjust the position of one wire, thus changing the relative angle and distance between the two wires. This way the size and taper of the micro rods can be controlled. The feasibility of the proposed TS-WEDG approach has been experimentally verified. The results have shown that TS-WEDG is a promising method for efficiently fabricating micro rods having either a positive or a negative taper.

Experimental investigations on micro machining of high speed steel using WEDG

This paper reports the effects of machining parameters on material removal rate, surface roughness and circularity in cylindrical wire electric discharge grinding (WEDG) of high speed steel. A rotary axis spindle is set up in the wire electric discharge machine in a submerged dielectric environment so as to machine cylindrical parts. The speed of the rotary axis spindle is maintained constant at 200 rpm. Experiments have been carried out under different process conditions like pulse current, open circuit voltage, pulse off time, servo voltage and number of passes. To obtain the best surface quality, the most significant parameters were identified. From the optimised wire electric discharge grind process micro pins were manufactured.

Experimental investigations on micro machining of high speed steel using WEDG

This paper reports the effects of machining parameters on material removal rate, surface roughness and circularity in cylindrical wire electric discharge grinding (WEDG) of high speed steel. A rotary axis spindle is set up in the wire electric discharge machine in a submerged dielectric environment so as to machine cylindrical parts. The speed of the rotary axis spindle is maintained constant at 200 rpm. Experiments have been carried out under different process conditions like pulse current, open circuit voltage, pulse off time, servo voltage and number of passes. To obtain the best surface quality, the most significant parameters were identified. From the optimised wire electric discharge grind process micro pins were manufactured.

Manufacturing of Micro Electrode through Wire Electric Discharge Grinding [WEDG] and Optimize the Machining Parameters

Manufacturing of Micro Electrode through Wire Electric Discharge Grinding [WEDG] and Optimize the Machining Parameters

Development of Numerical Model and Comparison with the Analytical Model for Predicting the Wire Effects in Wire Electric Discharge Grinding

Abstract This paper discusses the development of a numerical model and its comparison with the analytical model to predict the wire deflection in WEDG. The movement of wire between upper and lower guides creates vibration during the machining process which can create micro deflection of the wire. The Finite Element Analysis model [FEA] for the wire deflection is analyzed and compared with the analytical model. The deflection of the wire due to the input current may affect the machining of micro parts, which will be used for further research in micro machining and also will help us to choose the parameters such as current, spark gap, wire feed, and the speed of the workpiece during micro machining with WEDG. The FEA results for various forces were compared with the analytical results and found that the developed numerical model results are in good agreement.

Fabrication of micro holes in CFRP laminates using EDM

Carbon fiber reinforced plastics (CFRPs) are being used in various applications due to their light weight and good mechanical properties. However, the machinability of CFRPs is not good owing to machining induced damage. Moreover, the machining of micro features in CFRP products is a challenging task. The present research endeavour is an attempt to experimentally investigate a novel micro-size through hole electric discharge drilling (EDD) process for CFRPs. Through holes of diameter 110 μm were drilled using tungsten carbide electrodes (fabricated with wire electric discharge grinding). Experiments have been conducted by selecting input variables as voltage, capacitance and tool speed. A comparison of aspect ratio has been performed among the previous experimental studies and the current investigation. An aspect ratio of 10.9 (highest till date) has been achieved during drilling a micro hole of 110 μm diameter and 1.2 mm depth. Analysis of variance has been performed using Taguchi design of experiments and optimized set of parameters has been reported for maximum material removal rate and minimum tool were rate. The article also discuss the problems faced and their solutions, during drilling of micro through holes in carbon fiber reinforced polymer matrix composites.

Investigation on manufacturing of microtools made of tungsten carbide using wire electric discharge grinding (WEDG)

Wire electric discharge grinding has been developed to generate cylindrical profiles on hard-to-machine microparts. The outcome of the part is influenced by the process conditions and the rotational speed of the spindle. This paper investigates the effects of machining parameters on material removal rate (MRR), surface roughness and circularity during wire electrical discharge grinding process of tungsten carbide workpiece. Experiments have been carried out by varying process conditions such as peak current, open circuit voltage, pulse off time, servo voltage and number of passes. Pulse current has the highest significance to obtain maximum MRR. To obtain the best surface quality, pulse current, number of passes and pulse off time are identified as the most significant parameters. Using the technique of order preference by similarity to ideal solution, the optimal conditions estimated are pulse current (38 A), open circuit voltage (60 V) and pulse off time (24 µs) for finish machining.

Investigation of Machining Parameters for Hss in Wire Electrical Discharge Grinding

Investigation of Machining Parameters for Hss in Wire Electrical Discharge Grinding