Wire Tool Electrode Research Articles

Surface Quality of Carbide Metal After Electrical Discharge Machining

Recently, the requirements for machining shape-complex products made of hard-to-machine materials, including carbide, have been increasing significantly. However, their machining is rather problematic. Additionally, a high-quality standard of the machined surface is generally required, not only in terms of roughness but also in terms of the geometric accuracy of the machined surface. All this while maintaining a high level of economy in the machining process. However, meeting these demanding requirements in real technical practice is not always an easy task. Moreover, in combination with modern machining processes, only a limited number of production technologies can meet this requirement. Therefore, due to the high demands placed on today's modern production and the required high standard of the machined surface, progressive EDM technology is increasingly finding its application. And it is through this progressive technology that it is possible to achieve relatively good success in carbide machining. The aim of this paper was therefore to describe in detail the results of an experimental investigation aimed at identifying the quality of the machined surface achieved in terms of the roughness parameters of the machined surface in the electrical discharge machining of selected types of carbides using a wire tool electrode.

Efficiency of the Machining Process of Circular Shapes by Electrical Discharge Technology

Due to its high machining precision, EDM technology is nowadays very important in the production of high-precision parts for various industries. The high precision of the machined surface in combination with the ability to machine circular surfaces brings, in addition to several advantages, some negatives. The most significant negative of this machining technology is the relatively low productivity as well as the overall production efficiency. The latter is affected by many accompanying phenomena. The main accompanying phenomenon that contributes to the decline in the overall economic efficiency of EDM is the microgeometry errors that occur due to the non-homogeneity of the EDM process. Another accompanying negative phenomenon is the geometric accuracy errors of the machined surface, as a consequence of systematic destruction of the wire tool electrode, faulty interpolation in its guidance, and, last but not least, its vibration. These aspects consequently lead to the requirement for multiple applications of additional finishing cuts, which significantly reduces the overall economic efficiency of the machining process. Therefore, the experimental research aimed to search for options that can effectively help to achieve higher productivity but especially the overall economic efficiency of the machining process.

GEOMETRIC PRECISION OF THE CYLINDERS SURFACES MACHINED WITH WEDM TECHNOLOGY

One of the progressive production technologies through which it is possible to machine complicated shapes in materials characterized by high hardness is electrical discharge machining with a wire electrode. However, as with other progressive technologies, in the case of electrical discharge machining technology, demanding customer requirements for the geometric accuracy of the machined surface are not always met. These errors occur for various reasons. These are, for example, the vibrations of the wire tool electrode, its destruction during the machining process, the setting of technological and process parameters, but also errors in the design of the machine and the software control of the tool path. These and other errors have a primary role in the emergence of geometric inaccuracy of the machined surface after electrical discharge machining with a wire tool electrode. A special problem in the case of electrical discharge technology is the machining of internal and external cylindrical surfaces. As a result of the mentioned causes, deviations occur during their machining, which subsequently cause problems for the manufactured products during their assembly as well as the operation itself. Therefore, the objective of the experimental research was to identify the extent of these geometric deviations on the inner and outer cylindrical surfaces during electrical discharge machining with a wire tool electrode.

Identification of geometric errors of circular profiles at WEDM caused by the wire tool electrode vibrations and their reduction with support of acoustic emission method

High geometric precision of the machined surface after Wire Electrical Discharge Machining (WEDM) is in present one of the key quality parameters placed on machine parts manufactured for a wide range of industries. Despite the fact that WEDM belongs to the most precise finishing technologies, the deviations from the required geometric shape occur in the production of parts with rotary surfaces. These geometric deviations subsequently manifest in practice not only in the assembly of individual parts of the final product, but also in the operation. Another not the less important criterion considered at WEDM is the productivity of the WEDM process itself. WEDM productivity, in turn, is associated with the low overall productivity due to the need to apply multiple finishing cuts to achieve the desired quality of the machined surface in terms of geometric accuracy. Based on the already performed research, it is clear that the deviations of the geometric accuracy of the machined surface after WEDM are mainly caused by the vibrations of the wire tool electrode. Therefore, by eliminating these vibrations, it would be possible to achieve a substantial increase of the quality of the eroded surface, and thus reduce the number of finishing cuts. Ideally, the required quality level of the machined surface would be achieved right at the first cut. This would significantly increase productivity, enabling the WEDM technology to compete with other technologies in terms of productivity. In order to eliminate these undesirable vibrations of the wire tool electrode and to increase the quality of the machined surface after WEDM in terms of its geometric accuracy, the technical solution was proposed that applies the method of acoustic emission or laser beam vibration sensing in order to dynamically adjust the current values of technological parameters by the control system of the electroerosion machine. This way the given solution will increase the production accuracy of the circular holes, save the production time, increase the productivity, and ultimately bring the overall increase of the WEDM process economic efficiency.

Dynamic Control of Discharge Energy During WEDM for the Purpose of Eliminating Vibrations of the Wire Tool Electrode

Abstract Production in all industry fields is currently affected by new scientific and technical knowledge and the requirements for its rapid deployment. In many cases, the most modern and highly sophisticated technical systems are applied. Simultaneously, fully automated production systems are rather successfully used and progressive production technologies are implemented. In most cases, there is an integral part of a management system that operates the challenging technological processes. These processes would not be executable without the system’s precise control, which provides a suitable precondition for ensuring the high quality of manufactured products. However, the customer’s demanding requirements are not always met. These involve increased requests for the quality of the final product due to the reduction of the tolerance band and application of high-strength materials. This paper aims to describe one of the solutions by which it is possible to achieve a higher quality of the machined surface after wire electrical discharge machining (WEDM). The solution proposes that through dynamic management, the WEDM process eliminates the vibrations of the wire tool electrode and thereby achieves a substantial increase in the quality of the eroded area in terms of its geometric accuracy. With the support of an extensive database of information with precise exchange of information, the proposed system will allow to control the electro discharge process with regard to the optimal way of operation of the electro discharge machine on the basis of individually selected conditions.

Sub-Microstructure of Surface and Subsurface Layers after Electrical Discharge Machining Structural Materials in Water

The material removal mechanism, submicrostructure of surface and subsurface layers, nanotransformations occurred in surface and subsurface layers during electrical discharge machining two structural materials such as anti-corrosion X10CrNiTi18-10 (12kH18N10T) steel of austenite class and 2024 (D16) duralumin in a deionized water medium were researched. The machining was conducted using a brass tool of 0.25 mm in diameter. The measured discharge gap is 45–60 µm for X10CrNiTi18-10 (12kH18N10T) steel and 105–120 µm for 2024 (D16) duralumin. Surface roughness parameters are arithmetic mean deviation (Ra) of 4.61 µm, 10-point height (Rz) of 28.73 µm, maximum peak-to-valley height (Rtm) of 29.50 µm, mean spacing between peaks (Sm) of 18.0 µm for steel; Ra of 5.41 µm, Rz of 35.29 µm, Rtm of 43.17 µm, Sm of 30.0 µm for duralumin. The recast layer with adsorbed components of the wire tool electrode and carbides was observed up to the depth of 4–6 µm for steel and 2.5–4 µm for duralumin. The Levenberg–Marquardt algorithm was used to mathematically interpolate the dependence of the interelectrode gap on the electrical resistance of the material. The observed microstructures provide grounding on the nature of electrical wear and nanomodification of the obtained surfaces.

Adjustment of Wire Vibrations in Order to Improve Geometric Accuracy and Surface Roughness at WEDM

Although WEDM is one of the most precise finishing technologies, deviations from the required geometric shapes and surface roughness occur in the production of parts with rotary surfaces. Even though these shortcomings have only a minimal impact on planar cuts, the production of circular profiles is a different problem. One of the factors causing this poor quality is the vibration of the wire electrode. With appropriate vibration adjustment, it would be possible to achieve significant improvements of the eroded area quality, both in terms of geometric accuracy and in terms of surface roughness. This would significantly increase quality, enabling WEDM technology to compete with other technologies in terms of economic efficiency. Therefore, the proposed solution aims to provide a partial adjustment to the wire tool electrode vibrations, based on their sensing by the means of acoustic emissions or a laser beam, with subsequent dynamic adjustment of the actual technological parameter values. This way, the given solution will increase the production accuracy of circular holes, increase productivity, and ultimately provide an overall increase in the economic efficiency of the WEDM process. The article also presents the scheme of a control algorithm for monitoring and subsequent adjustments of the vibrations of the wire tool electrode during the electroerosion process in order to minimize geometric deviations of circularity, cylindricity and roughness of the machined surface.

Research of micro EDM/ECM method in same electrolyte with running wire tool electrode

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C1, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.

Precision electrochemical machining of tungsten micro-rods using wire electrochemical turning method

The novel wire electrochemical turning (WECT) method has been proposed to machine tungsten with neutral electrolyte and bipolar pulse current in the authors’ previous research. The influence of tool wear caused by the bipolar pulse current, which is needed to remove the oxide layer generated on tungsten surface when using a neutral electrolyte, was eliminated by the WECT method because the wire tool electrode was kept being wound during the machining process. In this paper, the influences of the most important process parameters, such as the kind of electrolyte, wire material, wire diameter, rotation speed of the workpiece rod, and frequency of the pulse voltage, were studied to understand the fundamental aspects of the WECT method and improve the machining efficiency of tungsten micro-rods. The experimental results showed that the NaCl electrolyte and the NaNO3 electrolyte had higher machining efficiency and better machining accuracy, respectively. The machining accuracy was improved with the SUS304 stainless steel wire used as tool electrode than the brass wire tool electrode. It was also found that the machining efficiency and accuracy were improved with decreasing the wire diameter and increasing the rotation speed of workpiece because the influence of stray current flowing through the side and end surface of machined micro-rod was reduced. The machinable length of micro-rod peaked at an optimum feed speed of the workpiece, and the optimum speed increased with increasing the frequency of pulse voltage. As a result, a minimum rod diameter of 11 μm was fabricated with a high aspect ratio of 36. Compared with the previous method using a platinum film as tool electrode, the aspect ratio was increased significantly because the influence of tool wear was eliminated.

Investigation of Surface Roughness for Inconel 625 using Wire Electric Discharge Machining

Due to the increase in the demand of materials with good surface finish and complex shapes, conventional machining processes became out of date. This directed to the increasing demand of non-conventional machining processes. This research work is focuses on the optimization of Surface Roughness (SR) using Wire Electrical Discharge Machining (WEDM) method on Inconel 625 super alloy material. The diffused wire tool electrode (plain and cryo-treated) is used for experimental work. Taguchi’s L18 (21*35) orthogonal array’s has been used to design for experimental run. The machining parameters selected for optimization are tool electrode, current (Ip), pulse on time (Ton), pulse off time (Toff), wire feed (Wf) and wire tension (Wt). Rectangular slits has been fabricated, which are useful for many industrial application like increase the heat transfer rate of fluids, micro-channels, micro-fins etc. Design of Experiment (DoE) optimization technique is used to find the most significant factor.

Development of EDT Equipment Using Wire Tool Electrode

Whirling electrical discharge texturing (WEDT) was developed to process microstructures on the inner surface of cylindrical parts made of high hardness materials. However, the minimum processable diameter of the cylindrical parts was φ 5 mm and the equipment could not feed the new tool electrodes. Therefore, the authors devised a novel method of WEDT using a straight wire tool electrode for a cylindrical surfaces with a small diameter. It was confirmed that microstructures could be created on the inner surface of a cylinder of φ 1.1 mm diameter, and that the texture-area ratio could be controlled by the workpiece feed speed. Moreover, new EDT equipment with a feeding system for a wire tool electrode and a bending system for the tip of a wire tool electrode was developed. As a result, the equipment that can process microstructures on the inner surface of a cylinder with a small diameter and feed a wire tool electrode during texturing was successfully developed.

Study of wire tool-electrode behavior during electrical discharge machining by vibroacoustic monitoring

In the current study, the full research of wire electrode behavior during electrical discharge machining is presented. The analysis of the work preparation processes gave a possibility to clarify the main parameters (factors) influencing on the final characterization of the obtained object. For the experiments, the system MACHINE-TOOL-WORKPIECE was established. The system was equipped by vibro-acoustic accelerometers to register the signals during processing. Processing of two work pieces from stainless steel 12Kh18N10T (analogue AISI 321) and aluminum alloy D16 gave the characterization of the material behavior. Further, the analysis of SEM pictures gave the important data about the character of wire tool wear during processing. The two main natures of the wire tool wear were recognized. The scheme of the wire tool wear for rough and finish cuttings was developed to demonstrate the results of the research.

Development of EDT Equipment Using Wire Tool Electrode

Development of EDT Equipment Using Wire Tool Electrode

Modeling and numerical simulation of electrochemical micromachining

The electrochemical machining using the numerically controlled motion of wire tool-electrode is studied theoretically. The Laplace equation for the electrical field potential and the equation of workpiece surface evolution are used as the mathematical model of the process. The developed scheme of computer modeling of machining involves the computation of distribution of current density over the workpiece surface using the boundary element method; the determination of new position of workpiece surface taking into account possible topological changes and the motion of tool-electrode along the prescribed trajectory. Various schemes of electrochemical micromachining using the tool electrodes with various cross-section shapes and various types of motions are analyzed.

Optimization of the Wire Electrical Discharge Machining Process Using Grey Relational Analysis and Taguchi Method

The wire electrical discharge machining is a machining method able to allow detaching parts from plates type workpieces as a consequence of electrical discharges developed between workpiece and wire tool electrode found in a motion along its axis; there is also a work motion along the contour to be obtained. There are many factors able to exert influence on the sizes of parameters of technological interest. On the other hand, there are various methods that can be used in order to establish the optimal combination of the input factors, so that obtaining of machining best results is possible. When there are many process output factors, a problem of multiobjective optimization could be formulated. The Grey relational analysis method and the Taguchi method could be applied in order to optimize the wire electrical discharge machining process, when various criteria having distinct significances are considered. An experimental research was designed and developed in order to optimize the wire electrical discharge cutting of parts made of an alloyed steel, by considering six input factors: test piece thickness, pulse on time, pulse off time, wire axial tensile, current intensity and travelling wire electrode speed. As output parameters, one took into consideration surface roughness, wire tool electrode massic wear, cutting speed along the contour to be obtained. 16 experiments were developed in accordance with the requirements specific to a Taguchi table L16. The results of experiments were processed by means of Grey relational analysis method and Taguchi method.

Surface Roughness at Wire Electrical Discharge Machining

Wire electrical discharge machining is a machining method by which parts having various contours could be detached from plate workpieces. The method uses the electrical discharges developed between the workpiece and the wire tool electrode found in an axial motion, when in the work zone a dielectric fluid is recirculated. In order to highlight the influence exerted by some input process factors on the surface roughness parameter Ra in case of a workpiece made of an alloyed steel, a factorial experiment with six independent variables at two variation levels was designed and materialized. As input factors, one used the workpiece thickness, pulse on time, pulse off-time, wire axial tensile force, current intensity average amplitude defined by setting button position and travelling wire electrode speed. By mathematical processing of the experimental results, empirical models were established. Om the base of a power type empirical model, graphical representations aiming to highlight the influence of some input factors on the surface roughness parameter Ra were achieved. The power type empirical model facilitated establishing of order of factors able to exert influence on the surface roughness parameter Ra at wire electrical discharge machining.

Modeling of Wire Electrochemical Micromachining

Wire electrochemical micromachining (WECMM) is a promising method for the fabrication of various metal parts. In recent years, WECMM has attracted increasing interest, especially for treatment of complex-shaped microworkpieces. By now, the regularities of electrochemical shaping for the complex-shaped workpieces have not been adequately investigated, because the majority of the works, which are devoted to WECMM, are experimental.In this work WECMM is studied theoretically. The Laplace equation for the electric potential and the equation of workpiece surface evolution are used as the mathematical model of the process. A scheme of computer simulation involves the numerical solution of the Laplace equation by the boundary element method; the determination of a new position of workpiece surface with regard for possible topological changes; and the motion of wire tool-electrode along a prescribed trajectory. Various schemes of shaping for the tool-electrodes with various cross-section shapes and various types of motions are analyzed. As a result of simulation, the dependences of the front and side interelectrode gaps on the machining parameters are obtained. They can be used for determining the path of wire tool-electrode in order to obtain the prescribed shape and sizes of workpiece surface.

Device for Wire Electrical Discharge Machining

The problem approached in this paper refers to designing a device for wire electrical discharge machining (EDM) which can be used on a ram electrical discharge machine. Usually, wire electrical discharge machine is applied only on specialized electrical discharge machines. The device proposed in the paper will ensure widening the technological possibilities of the given ram EDM equipment. A principle schema of the device was established, after analyzing the main requirements specific to the device service. One took into consideration a possibility to rotate and fix the subassembly for guiding the wire electrode so that the active zone of the wire tool electrode has a horizontal, vertical or even inclined position. Another requirement was to ensure a way for achieving machining processes in cavities existing in workpieces of higher dimensions. Functioning of the designed device and strain resistance of some components were tested by using CATIA V5 software. Some optimization possibilities for this constructive solution of the device were identified.

Improving the WEDM Process Acting on the Tool Electrode

Abstract The wire electrical discharge machining is based on the developing electrical discharges between a travelling wire tool electrode and a plate workpiece, in order to detach parts characterized by machined ruler surfaces. The practical experience and the study of the specialty literature highlighted the possibilities to improve the material removal rate by acting on the wire tool electrode. Two versions of devices able to periodically change the wire traveling motion speed are discussed and proposed; the devices could be included in the circuit of guiding the wire electrode on the wire electrical discharge machine.

Study of the dynamics of the process of electric discharge sawing by wire tool electrode

The article presents the results of experimental and theoretical studies of the dynamics of the process of electric discharge sawing by wire tool electrode aimed at solving problems of control.