Search

Shape memory alloys (SMAs) are potential materials in various areas such as engineering and medicine, and their applications are being studied for practical use. SMAs show competence in their main material properties in response to their working environment or external stimuli. Machining of NiTiCu10 SMAs is difficult using traditional machining because of their wide-ranging mechanical properties like high toughness, strength, and sensitivity to phase transformation temperature. Nonconventional machining methods such as electro-discharge machining (EDM) are suitable for effective machining SMAs. The work material NiTiCu10 SMA has been used in this study, and processed using the vacuum induction melting (VIM) technique. The addition of copper leads to increase in the martensitic transformation temperatures. This paper focuses on the electro-discharge drilling (EDD) of NiTiCu10 SMA using copper tool electrode. Experimental analysis of performance criteria has been evaluated by conducting experiments following one factor at a time (OFAT) approach. Machining features such as material removal rate (MRR), tool electrode wear rate (TEWR), and surface roughness (SR) have been studied by considering pulse current ( I p ), gap voltage ( V g ), pulse on time ( T on ), pulse off time ( T off ), and rotational speed of tool electrode (N). Experimental results have shown that machining at the highest I p of 12 A yields the highest MRR with the value of 4.077 mm3/min, whereas mcahining at T on of 15 μ s yields the lowest TEWR with the value of 0.031 mm3/min. The lowest SR is 2.8 μ m achieved at the lowest T on of 15 μ s. Surface morphology is significant in quality evaluation in the manufacturing, and building industries because it directly determines the mechanical performance of parts, and the service life of products. Morphological investigation via scanning electron microscope (SEM) has confirmed the formation of craters, debris, microcracks, and resolidified layers. The benefit of this study has been that we have been able to select the range of significant control factors, and predict their levels, for decisive experimentation. [ABSTRACT FROM AUTHOR]

Machining characteristics were applied to topology optimization for machine tool structure design improvement in this study, and the goals of lightweight and high rigidity of the structure were achieved. Firstly, an ultrasonic-assisted grinding experiment was carried out on zirconia to investigate the surface roughness, surface morphology, grinding vibration, and forces. Then, the topology optimization analysis was conducted for structure design improvement, in which the magnitude of the grinding vibration was utilized as the reference for selecting the topology subsystems and the grinding force was used as the boundary conditions of the static analysis in the topology optimization. Hence, columns, bases, and saddles were redesigned for structure stiffness improvement, and the variations in the effective stress, natural frequency, weight, and stiffness of the whole machine tool were compared accordingly. The results showed that the deduced topological shape (model) can make the natural frequency and stiffness of the whole machine tool tend to be stable and convergent with a weight retention rate more than 75% as the design constraint. The subsystem structures with larger effective stress distributions were designated for stiffness improvement in the design. At the same time, the topological shape (model) was also employed in the design for weight reduction, focusing on minimizing redundant materials within the structure. In contrast to the consistency of the modal shapes before and after topological analysis, the sequential number of the modal mode of the machine tool model after topological analysis was advanced by two modes relative to those of the original situation, which means the original machine tool may be out of its inherently resonant frequency range. Also, the natural frequencies corresponding to each mode had an increasing tendency, and the maximum increase was 110.28%. Furthermore, the stiffness of the machine tool also increased significantly, with a maximum of 355.97%, leading to minor changes of the machine tool's weight. These results confirm that the topology optimization based on machining characteristics proposed in this study for structure redesign improvement and stiffness enhancement is effective and feasible. [ABSTRACT FROM AUTHOR]

In this paper, a magnetic field-assisted WEDM-ECM complex process (MF-assisted WEDM-ECM) is proposed to solve the problems of traditional low-speed wire electrical discharge machining (WEDM-LS) of NiTi SMA, including low machining efficiency, high workpiece surface roughness, and large recast layer thickness. Electrolytic machining is used to remove the recast layer, and magnetic field-assisted method is used to reduce the surface roughness and improve the machining efficiency. Firstly, based on the double-layer model the removal thickness of recast layer is deduced, and the removal thickness of recast layer under different machining parameters is analyzed. In addition, based on the influence of magnetic field on discharge channel, the single spark crater analytical model is modified. Based on this model, combined with the electrochemical corrosion rate and the wire electrode vibration response equation, a continuous discharge corrosion mathematical model is established to predict the surface topography of the workpiece, and the simulation analysis is carried out. Finally, comparison of the experimental results of traditional WEDM-LS, MF-assisted WEDM-LS, ultrasonic vibration (USV)-MF complex-assisted WEDM-LS, and MF-assisted WEDM-ECM in machining NiTi SMA reveals that MF-assisted WEDM-ECM has the best machining performance. Compared with traditional WEDM-LS, the material removal rate (MRR) of MF-assisted WEDM-ECM was increased by 26.2%, the surface roughness value was reduced by 19.2%, and the thickness of recast layer was reduced by 44.25%. The average errors of the experimental and predicted values of workpiece surface roughness, recast layer removal thickness, and kerf width are 8.3%, 6.41%, and 3.58%, respectively, which verified the accuracy of the theoretical model proposed in this paper. [ABSTRACT FROM AUTHOR]

In die-sinking electrical discharge machining (EDM), it is challenging to implement internal flushing, mainly because it is easy to produce residual material columns on the workpiece cavity's bottom surface, affecting the processing quality and efficiency. In order to solve this problem, the internal flushing slotted electrode EDM technology was proposed. The slotted electrode was designed, and its preparation method was described. The influence of pulse width, pulse interval, and flushing pressure on the performance of the internal flushing slotted electrode EDM was studied using single-factor experiments. The experimental results indicate that, with the increase in pulse width, the material removal rate (MRR) increases first and then decreases, while the electrode wear rate (EWR) and the relative electrode wear rate (REWR) decrease gradually; with the increase in pulse interval, the MRR decreases, while the EWR and the REWR increase gradually; with the increase in flushing pressure, the MRR increases first and then decreases, while the EWR and the REWR increase gradually. When the slotted electrode is used for continuous internal flushing EDM, the appropriate pulse width, flushing pressure, and smaller pulse interval can improve the MRR and reduce the EWR and the REWR. [ABSTRACT FROM AUTHOR]

Aloevera loomed mat and porous Punica Granatum peel (pomegranate) biochar particles are utilised in this study to create high-toughness epoxy bio-composites for low-cost, light-weighted applications. The purpose of this study was to see how a silane-treated aloevera fibre with silane-coated biochar particles added at various concentrations influences the high-speed drilling and mechanical characteristics of epoxy composites. The high porous biochar particles were prepared from dried pomegranate peels via a low-temperature pyrolysis process. Subsequently, both the fibre and particles are silane-treated using ethanol based aqueous solution bath. The composites were prepared via cold open mould hand layup setup and post-cured at 120 °C in a hot air oven. Results revealed that the composite containing silane-treated aloevera fibre with loading fractions of 40vol.% and 3vol.% surface modified biochar particles have the maximum tensile strength and modulus, flexural strength and modulus, impact toughness, hardness and adhesion strength of 154 MPa, 5.12 GPa, 244 MPa, 6.71 GPa, 7.1 J, 92 shore-D, and 26.3 MPa, respectively. Similarly, with a particular wear rate of 0.006 mm3/Nm and a coefficient of friction (COF) of 0.34, for the 57/0/40/0/3 composite that exhibits superior tribology behaviour. Moreover, the silane-treated fiber, as well as biochar particles, derived epoxy composites shows high dimensional stability in both smaller and bigger diameter holes. There is no fibre pullout seen on the edges of the drilled portion on the silane-treated composite. These epoxy biocomposites with better mechanical and good machining characteristics could be useful in a variety of engineering applications needing high load bearing capacity and biodegradability, including automobiles, sporting goods, domestic sector, transportation, and aircraft. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Machining characteristics were applied to topology optimization for machine tool structure design improvement in this study, and the goals of lightweight and high rigidity of the structure were achieved. Firstly, an ultrasonic-assisted grinding experiment was carried out on zirconia to investigate the surface roughness, surface morphology, grinding vibration, and forces. Then, the topology optimization analysis was conducted for structure design improvement, in which the magnitude of the grinding vibration was utilized as the reference for selecting the topology subsystems and the grinding force was used as the boundary conditions of the static analysis in the topology optimization. Hence, columns, bases, and saddles were redesigned for structure stiffness improvement, and the variations in the effective stress, natural frequency, weight, and stiffness of the whole machine tool were compared accordingly. The results showed that the deduced topological shape (model) can make the natural frequency and stiffness of the whole machine tool tend to be stable and convergent with a weight retention rate more than 75% as the design constraint. The subsystem structures with larger effective stress distributions were designated for stiffness improvement in the design. At the same time, the topological shape (model) was also employed in the design for weight reduction, focusing on minimizing redundant materials within the structure. In contrast to the consistency of the modal shapes before and after topological analysis, the sequential number of the modal mode of the machine tool model after topological analysis was advanced by two modes relative to those of the original situation, which means the original machine tool may be out of its inherently resonant frequency range. Also, the natural frequencies corresponding to each mode had an increasing tendency, and the maximum increase was 110.28%. Furthermore, the stiffness of the machine tool also increased significantly, with a maximum of 355.97%, leading to minor changes of the machine tool’s weight. These results confirm that the topology optimization based on machining characteristics proposed in this study for structure redesign improvement and stiffness enhancement is effective and feasible.

Micro texture tools (MTTs) with variable distribution density were proposed, and the novel MTTs can adapt to different friction states in the tool chip contact area and maintain good anti-friction and wear resistance. The novel MTTs were composed of two regions with different groove width and distribution density which were prepared on the rake face by femtosecond laser technology. The cutting processes were carried out in turning superalloy GH4202. According to the machining characteristics (rake wear, tool wear volume, workpiece material adhesion volume, and the chip morphology), the role of variable distribution density in turning was analyzed. The experimental results showed that the texture parameters of the texture region near and away from the edge have different effects and mechanisms on the machining characteristics. Compared with a non-textured tool and uniform textured tool, the proper design of texture parameters of variable distribution density texture can make the MTTs have better wear resistance and chip breaking ability when turning superalloy GH4202. [ABSTRACT FROM AUTHOR]

With the development of additive manufacturing (AM) technology, many studies on wire arc additive manufacturing (WAAM) have been conducted due to its low production costs and high fabrication speed. Degree of freedom of the shape is a limitation of conventional machining (CM) that can be overcome by WAAM. Owing to the low level of shape completeness and surface roughness, post-processing through machining is needed. Plasma-assisted machining (PAM) is an effective method that improves the machinability of difficult-to-cut materials by softening the material by preheating using a heat source. In this study, CM and PAM of 304 stainless steel (SS) manufactured using WAAM were explored. Each 304 SS workpiece was manufactured using WAAM in X, Y, and Z directions. The experimental results were evaluated by conducting tensile tests and performing microstructural analysis. The machining conditions for PAM were selected via thermal analysis. Moreover, the post-machining effect was analyzed by measuring the cutting force, surface roughness, hardness, and microstructure. In addition, CM and PAM of 304 SS manufactured by casting were performed to compare the machining characteristics with those of the workpieces manufactured using WAAM.

In die-sinking electrical discharge machining (EDM), it is challenging to implement internal flushing, mainly because it is easy to produce residual material columns on the workpiece cavity’s bottom surface, affecting the processing quality and efficiency. In order to solve this problem, the internal flushing slotted electrode EDM technology was proposed. The slotted electrode was designed, and its preparation method was described. The influence of pulse width, pulse interval, and flushing pressure on the performance of the internal flushing slotted electrode EDM was studied using single-factor experiments. The experimental results indicate that, with the increase in pulse width, the material removal rate (MRR) increases first and then decreases, while the electrode wear rate (EWR) and the relative electrode wear rate (REWR) decrease gradually; with the increase in pulse interval, the MRR decreases, while the EWR and the REWR increase gradually; with the increase in flushing pressure, the MRR increases first and then decreases, while the EWR and the REWR increase gradually. When the slotted electrode is used for continuous internal flushing EDM, the appropriate pulse width, flushing pressure, and smaller pulse interval can improve the MRR and reduce the EWR and the REWR.

Abstract Electrochemical machining (ECM) is a process that is widely employed to machine extremely hard materials. However, because of the fluidity of the liquid electrolytes used in conventional ECM, it is difficult to accurately limit the electrolyte distribution over the machining area to prevent the occurrence of stray-current corrosion. Therefore, in this study, to overcome this shortcoming, a non-conductive solid porous ball is used as an electrolyte absorption material in ECM. The electrolyte is absorbed by the porous structure of the ball, and an electrolyte film is formed on the ball surface generating current paths from the workpiece to the tool electrode while preventing the electrolyte from flowing freely in an undesired manner over the workpiece surface. Because the workpiece is not immersed in the electrolyte, only the area in contact with the electrolyte held in the porous ball is subjected to ECM, whereas the other areas of the workpiece remain unaffected. In this way, the electrolyte distribution is limited to the desired area. In this paper, a newly developed experimental procedure, its machining mechanisms, and applications are explained. In addition, several unsolved problems that occurred in the experiments are reported and discussed. • The machining mechanism, features, and applications of ECM using electrolyte absorbed in solid porous ball are investigated and discussed. • To control the electrolyte distribution, a solid porous material was used as the electrolyte absorption material in ECM processing. • To better understand the machining characteristics of this method, a number of the factors influencing these characteristics are examined experimentally. [ABSTRACT FROM AUTHOR]

One main disadvantage of electrical discharge machining (EDM) is its low machining efficiency, which limits the further application of EDM. Comparing the spark discharge waveform and the arc discharge waveform under the transistor pulse power supply, it can be found that a high-frequency oscillation component is presented in the spark discharge waveform during the discharge, while the high-frequency oscillation component does not exist in the arc discharge waveform. Inspired by this phenomenon, a new pulse power supply with active high-frequency oscillation was developed in this study, which can provide rectangle pulse discharge current with high-frequency oscillation component. Experimental results show that compared with the traditional transistor type pulse power supply that only generates rectangle discharge current, the pulse power supply with active high-frequency oscillation component can improve the machining efficiency effectively and reduce the tool electrode wear without influencing the surface roughness. Further, the influences of the oscillation frequency and the oscillation amplitude of on the machining characteristics were investigated. In addition, under active high- frequency oscillation current, by the high-speed observation of the arc plasma, the measurement of the discharge craters and the statistics analysis of the effective discharge rate, the influence mechanism of active high-frequency oscillation current on the material removal of EDM was discussed. [ABSTRACT FROM AUTHOR]

The LC generator has many advantages in electrical discharge machining (EDM). It can generate high gap open voltage and high discharge current pulse with short duration under very low voltage input conditions. The shape of current pulse generated by the LC generator with higher rising speed shows superiority in machining efficiency compared to the conventional RC generator. This paper aims to investigate the influential parameters of the LC pulse generator and analyze how inductance, capacitance and switching frequency influence the discharge current pulse and gap open voltage pulse. The results of investigation are used to match the real discharge conditions by experiments. On the other hand, roughness of machined workpiece, cylindricity of drilled holes, tool wear ratio and material removal rate are investigated under different discharge parameters generated by the LC pulse generator. [ABSTRACT FROM AUTHOR]

In this paper, the slicing of a conductive SiC ingot is performed by an oil and a water type WEDM. The machining characteristics by the both type WEDM are investigated. The survey items are volumetric removal rate, average machined groove width, machined surface roughness, and machined surface properties. Regarding the results of the investigation with a discharge current of 1A, the volumetric removal rate of the water type WEDM is about 1.1 times faster than that of the oil type WEDM. Comparing the average machined groove widths, it of the water type WEDM is about 30% wider than that of the oil type WEDM. As a result, it was found that the surface roughness of the machined surface of water type WEDM was about 3 times as rough as the surface roughness of the machined surface of oil type WEDM. The machined surface properties of the both type WEDM are completely different. Specifically, the molten recast layer is hardly seen on the machined surface of the oil type WEDM, but it is clear that the machined surface of the water type WEDM is covered with the molten recast layer. This result suggests that the EDM phenomenon differs between the oil and the water type WEDM. From the above results, it was clarified that the oil type WEDM gives better results than the water type WEDM for slicing of a conductive SiC ingot. [ABSTRACT FROM AUTHOR]

Near-dry electrical discharge machining (EDM) is an environmentally friendly method that uses a two-phase atomized medium composed of gas and water as the discharge dielectric. The relevant research literature shows that the material removal rate (MRR) of steel materials processed by near-dry EDM with air medium (Air-NEDM) is higher than that of near-dry EDM with inert gas medium. However, the results of this present show that when argon is used as the gas medium for near-dry EDM (Ar-NEDM) to process titanium alloy, the MRR is more than 80% higher than that of Air-NEDM. Therefore, the material removal mechanism of near-dry EDM in air medium and argon medium is studied by single-pulse discharge experiment. Then, the effects of processing parameters such as current, pulse width, and gas pressure on MRR, relative electric wear rate (REWR), surface roughness (SR), and recast layer thickness (RLT) were studied through a one-factor-at-a-time approach. The results of single-pulse discharge experiment show that the discharge gap of Ar-NEDM is larger than that of Air-NEDM, and the discharge crater is also larger. The experimental results show that compared to Air-EDM, Ar-NEDM cannot only obtain higher MRR, but also can obtain a micro-surface without obvious microcracks and micropores, smaller SR, and thinner RLT, but its REWR is relatively high. [ABSTRACT FROM AUTHOR]

High strain rate can be produced in many manufacturing processes, such as ultra-high-speed machining and ultra-precision machining. This paper reviews the high strain rate generated in different machining processes. Molecular dynamics (MD) and finite element (FE) for studying the mechanism and characteristics in manufacturing processes are analyzed; the ductile–brittle transition (DBT) and brittle-ductile transition (BDT) under high strain rate are also reviewed. And the machining characteristics in ultra-high-speed cutting and ultra-precision cutting are analyzed and compared, including cutting force, cutting heat, machined surface quality, tool wear, and chip formation. It is proposed that the DBT under high strain rate in ultra-high-speed machining is contradictory with the BDT in ultra-precision machining, because the reasons for producing a high strain rate are different. By increasing the cutting speed vc in ultra-precision cutting appropriately, the machinability of softer materials may be increased, and surface and subsurface damage can be reduced. [ABSTRACT FROM AUTHOR]

In wire electrical discharge machining, due to the random distribution of the insulating SiC particles, frequent wire rupture, low machining efficiency and surface quality when the common brass wire electrode (BWE) is used to process high-volume content SiCp/Al composite often appears. To address this issue, this paper proposes a new preparation method of zinc coating and surface microstructure on wire electrodes (ZCSMWE). The preparation process of ZCSMWE includes casting, coating, annealing and plastic processing. The experimental results show that, compared with BWE, ZCSMWE can increase material removal rate (MRR) by 16.67%, reduce surface roughness (Ra) by 21.18% and reduce wire rupture under the same discharge parameters. The analysis of workpiece surface topography shows that ZCSMWE can significantly decrease the recast layer and microcrack on the machined surface. The improvement mechanism of ZCSMWE main includes: The low work function zinc can promote the forming of the discharge channel. The vaporization of low boiling temperature zinc can reduce the temperature of the discharge gap and promote the ejecting of workpiece material. In addition, the surface microstructure on ZCSMWE can make the discharge spark more uniformly distributed and increase the proportion of the effective discharge, which contributes to making the discharge crater on the workpiece and wire electrode shallower and more uniform. The surface microstructure on ZCSMWE can also effectively improve the dielectric circulation, which can promote discharge debris to be expelled out and reduce the temperature in the discharge gap. Then, the wire rupture and microcracks on the workpiece surface can be reduced. [ABSTRACT FROM AUTHOR]

WEDM (Wire electrical discharge machining) is a precision machining method for cutting electrically conductive materials. It is an unconventional machining process that produces precision parts that match the dimensional tolerances of our designs within the range of ±0.0001mm. As the residual stress results in premature failure of parts, the WEDM is preferred for hard to machine materials such as Inconel, Nickel, and other Super alloys. In the present paper, earlier and recent work was reviewed, segregated and evaluated on the effect of wire material, diameter, dielectric fluid, wire wear, pulse on and off times and machining characteristics such as kerf size, machining efficiency, material surface characteristics, etc. This paper also focused on hybrid and ultrasonic-assisted WEDM used for machining of different materials. This paper discussed the major research studies in WEDM.

This paper presents an investigation of the effects of the gas medium on the submersed gas-flushing electrical discharge machining (EDM) of different metal materials. Two metal materials, specifically TC4 titanium alloy and Cr12 steel, are selected as the processing objects, which are immersed in water-based working fluid. The material removal rates (MRRs), relative electrode wear rates, surface morphologies (SMs), and surface recast layers (SRLs) of these two materials during EDM were studied with both air and argon as the gas medium (Air-EDM and Ar-EDM, respectively). The experimental results showed that the MRR of Ar-EDM processing of TC4 is nearly four times that observed using Air-EDM. In contrast, the MRR of Ar-EDM processing of Cr12 is one seventh that found with Air-EDM. At the same time, a relatively thin SRL and an improved SM can be obtained by Ar-EDM with both TC4 and Cr12. During Air-EDM, heat is produced from oxidation reactions, which makes the MRR with Cr12 higher than that with TC4, and the quality of the surface morphology is poor. The results from simulations of single-pulse discharge show that the difference in thermal conductivity between TC4 and Cr12 is responsible for the different material removal rates during Ar-EDM machining. [ABSTRACT FROM AUTHOR]

Carbon fiber–reinforced plastic (CFRP) composites are extensively being applied in manufacturing sectors because of their extraordinary characteristics. However, CFRP composites often require some extra machining processes to improve the dimensional accuracy and component integrity of CFRP composites in manufacturing industries. The ultrasonic machining (USM) process progressively has been examined due to its greater ability in machining difficult to cut, brittle, and hard materials such as CFRP composites and due to its relatively low machining cost. Furthermore, USM shows to be a promising process with better surface quality, lower cutting force, less or no fiber fracture, laminate delamination, and lower tool wear rate. Recently, USM has been extensively investigated by many researchers for the machining of CFRP composites. This paper explores the literature and presents a comprehensive review of the advances in USM of CFRP composites by classifying the studies reported in two perspectives. First, the review summarizes most of the reported studies starting from 2011 to 2020 based on the applied USM process, equipment/system/platform used to carry out experiments, considered process parameters and output variables, and challenges investigated or gap filled. Then, the reported studies are summarized considering the type of USM process variant, CFRP composite, adopted process parameters on machining characteristics, and their respective results and conclusions. The aim is to present the current research status in USM of CFRP composites and thus provide guidance and foundation for future research. [ABSTRACT FROM AUTHOR]

This paper investigates the effects on the electrical discharge machining (EDM) characteristics of SKD 11 cold work tool steel when adding graphite (Gr) and boron carbide (B4C) powder to the dielectric fluid. The introduction of different concentrations of powders into the dielectric fluid modified the results of the machining process. This was then compared with the results from normal machining conditions. This study examined the dimension of the machined hole, material removal rate (MRR), electrode wear rate (EWR), and surface roughness (SR). The results obtained from this study indicate the powder concentrations in the dielectric fluid had an obvious effect on the machining characteristics. The MRR and EWR values increased when both the Gr and B4C powders were increased. However, the surface roughness of the workpiece only increased when the Gr concentration was increased. In contrast, the addition of B4C powder resulted in a significant decrease in the roughness of the workpiece surface. In conclusion, the addition of Gr at a concentration of 2 g/l produced better machining characteristics than those under normal machining conditions. MRR was increased by 22.68%, and the EWR and SR were decreased by 2.85 and 17.18%, respectively. [ABSTRACT FROM AUTHOR]

Inconel 825 is high nickel-chromium-based superalloy which retains its mechanical properties and exhibits good corrosion and oxidation resistance at elevated temperature. Inconel 825 is extensively used for making aircraft engine parts like combustor casing and turbine blades in aero space industry. This research proposed the Response Surface Methodology with GRA to optimize multiple responses during Wire-cut EDM of Inconel 825. At optimum combination of input parameters i.e. A4B1C1D5E4F2, increase in MRR from 36.13 mm2/min to 41.822 mm2/min, decrease in SR from 2.842μm to 2.445μm and decrease in WWR from 0.01832 to 0.01758 was obtained. Experimental results showed that pulse-on time, wire feed, pulse-off time, and peak current significantly affected the MRR, and surface integrity of specimen and electrode with the formation of craters, pockmarks, debris, micro cracks, and recast layer. The optimal parametric combination obtained from the present study will be advantageous for working on high strength; high thermal conductivity and low melting point materials like nickel alloys.

WEDM (Wire electrical discharge machining) is a precision machining method for cutting electrically conductive materials. It is an unconventional machining process that produces precision parts that match the dimensional tolerances of our designs within the range of ±0.0001mm. As the residual stress results in premature failure of parts, the WEDM is preferred for hard to machine materials such as Inconel, Nickel, and other Super alloys. In the present paper, earlier and recent work was reviewed, segregated and evaluated on the effect of wire material, diameter, dielectric fluid, wire wear, pulse on and off times and machining characteristics such as kerf size, machining efficiency, material surface characteristics, etc. This paper also focused on hybrid and ultrasonic-assisted WEDM used for machining of different materials. This paper discussed the major research studies in WEDM. [ABSTRACT FROM AUTHOR]

A rise in demand for silicon carbide in the semiconductor sector is often met with a setback due to the inability to machine them effectively. The high cost of the material further poses a significant challenge to reduce material losses during machining to a minimal level. Electrical discharge machining is an alternate approach that can machine various material regardless of the material's hardness, as long as they are electrically conductive in nature. The rapid hot press sintering technique is a material fabrication approach that relates to superior electrical and thermal characteristics without the addition of any additional fillers. Thus, the present work focuses on the fabrication of silicon carbide using rapid hot press sintering technique and subsequent identification of the influential parameters that best relates to a superior machining scenario in wire electric discharge machining. The effect of various process parameters (open voltage, servo voltage, pulse duration, wire speed, and wire tension) on the overall machining characteristics were carefully analyzed. The intensity of the discharge energy significantly influenced the crater formation on the workpiece surface, which directly affected the overall output characteristics. The variation in the concentration of discharge, open and arcing pulses with servo voltage resulted in varying output characteristics. A minimum kerf width of 165 μm was obtained in the current work with a wire electrode of diameter 150 μm, which considerably advances the step towards minimization of material loss. The detailed analysis of the machined surface suggested the removal of SiC by the combined action of melting, evaporation, and thermal spalling effect. Furthermore, the recast layer was observed to be porous due to severe oxidation and decomposition phenomena. [ABSTRACT FROM AUTHOR]

The design and optimization of standard parts to the machine tool is always being the focus of domestic and foreign countries,which is helping for the machine tool inspection and assessment of the performance. In this study,according to the advantages and disadvantages of standard specimen of the universal five-axis NC machine tools,comparing the structural characteristics and machine features for the testing performance of ISO international standard specimen, NASA979 series specimen,"S"shape of the specimen and other specimens. The most characteristics of modern aviation parts are combined to design the "X"form of new aircraft thin-wall standard specimen. By analyzing the "X"shaped aviation thin-walled specimen with the finite element method,the open,close angles and curvature continuity curves are calculated and discussed. Based on the results of finite element analysis,it’s the first time to put forward the processing complexity coefficient concept,compares the cutting force and thermal load,the cutting force dominates in the residual stress generated,this paper only consider the effect of cutting force,to evaluate the characteristics of the"X"shape aviation thin-wall specimen in the geometric model and mechanical structure design in-depth. It proved that "X"shaped aviation thin-wall specimen is better than the other standard specimens in comprehensively reflecting the multi-axis linkage and dynamic stiffness characteristics of the CNC machine possess,showing more comprehensive and superiority in the aspect of detection. All above conclusions provide the scientific basis and effective approach for integrated precision detection characteristic of five-axis CNC machine based on the "X "shaped new aircraft thin-walled standard specimen.

In wire electrical discharge machining (WEDM), increasing the machining characteristics is always a research hot spot. Now, magnetic-assisted method cannot directly improve the performance of WEDM during machining magnetic material. In addition, due to the defects of convergence precision, convergence speed, global optimization, and subjectivity, the application of individual parameter optimization algorithm is limited. In order to address these problems, this paper proposes magnetic-assisted method and modified non-dominated neighbor immune algorithm to ameliorate the performance of WEDM in trim cutting magnetic material. Firstly, the force analysis of debris and the analysis of discharge current waveform are carried out to clarify what setting condition of the magnetic field generator is proper. It is indicated that the magnetic-assisted method maybe improves the machining characteristics of WEDM when the Lorentz force has the same direction with dielectric flashing force during trim cutting magnetic material. Additionally, a set of trim cutting Taguchi experiment is accomplished to investigate the effect of magnetic-assisted method on material remove rate (MRR), surface roughness (SR), and recast layer thickness (RLT). Thereinto, it can be found that the machining characteristics of WEDM are obviously improved by magnetic-assisted method. More specifically, under magnetic-assisted method, MRR, SR, and RLT are improved by an average of 18.45, 17.86, and 17%, respectively. Then, on the basis of game theory, the modified non-dominated neighbor immune algorithm (NNIA) is proposed to select best process parameters for further increasing the machining characteristics of magnetic-assisted WEDM (MA-WEDM). Eventually, the comparative results of three algorithms and verification experiment demonstrate that this modified NNIA exhibits better optimization performance than NSGA-II and NNIA. Specifically, by modified NNIA, the largest increase of MRR and the greatest decrease of SR and RLT are 22.37, 44.59, and 15.07%, respectively. [ABSTRACT FROM AUTHOR]

One of the problems faced in the finish electrical discharge machining of cemented carbide is the slow machining speed due to frequent abnormal discharges and concentrated discharge. To resolve this problem, in this study, attempts were made to supply oxygen to oil-type non-flammable dielectric liquid used in finish electrical discharge machining. First, the effects of the form of the oxygen when it is supplied to the dielectric liquid were investigated. As a result, it was found that when oxygen is supplied to the machining gap in the microbubble state, machining is not affected at all. When dissolved in the dielectric liquid and supplied, machining speed was seen to improve. Next, machining experiments were conducted, varying the percentage of 35 wt% hydrogen peroxide water mixed with the dielectric liquid to change the amount of oxygen in the dielectric liquid. As a result, the following were clarified. (1) The machining speed was six times faster than normal dielectric liquid when 15 wt% of oxygen was mixed; (2) at this time, the tool electrode wear had decreased to one-fifth that of normal dielectric liquid; (3) the surface roughness obtained was below Ra 1µm regardless of the mixed percentage of hydrogen peroxide water; and (4) better machining characteristics were obtained when the workpiece was set as the positive electrode. [ABSTRACT FROM AUTHOR]

Micro electrical discharge machining (EDM) has been used to drill micro-holes and to generate micro-features for applications in automotive, aerospace and biomedical industries. The tool electrode wear ratio in micro-EDM usually is larger than that in conventional EDM process. It has been reported that the electrode wear ratio is almost zero in gas. However, its narrow discharge gap leads to frequent occurrence of abnormal discharges. In order to enlarge the discharge gap in micro-EDM, Nitrogen plasma jet (NPJ) has been used as the working media for micro-EDM in this study. NPJ is generated by using a needle-cylinder type corona discharge with an AC power supply in pure nitrogen gas. A RC-type pulse generator is used to realize micro electrical discharges in this investigation. It is expected that the electrons and ions in NPJ increase the electrical conductivity in the discharge gap. Thus, a large discharge gap can be obtained. To investigate the machining characteristics of micro-EDM in NPJ, series of experiments in NPJ, nitrogen jet (NJ) and deionized water (DIW) have been carried out. The discharge distance, machining time, electrode wear and surface roughness under different conditions have been recorded. The measured data has been analyzed together with the discharge signals. It was found that the discharge distance in NPJ is larger than that in NJ. The machining process in NPJ is much more stable than in NJ. The observed volumetric difference of electrode wear is very small, probably due to the small total material removal. The machining efficiency in DIW is the highest. However, the surface roughness in DIW is worse than that in NPJ. [ABSTRACT FROM AUTHOR]

It is well known that electrical discharge machining (EDM) is a machining method that does not affect the hardness of the material being processed. The EDM method is widely used for the finish machining of metal molds, for which materials having a high degree of hardness is used. However, the EDM method has a disadvantage in that the machining speed is remarkably slow compared to other machining methods. However, if the discharge energy is increased, the quality of surface finish is decreased. For this reason, it is difficult to machine a finished surface. In order to improve machining characteristics while using the same discharge energy, it is important to homogeneously disperse the discharge, so as to increase the rate of normal discharge, and to discharge the machining dust that accumulates between the electrode and workpiece. However, it is difficult to generate a constantly normal discharge in EDM. What is worse, the more deeply a hole is machined, the more difficult it is to remove the machining dust that accumulates between the electrode and the workpiece. A concentrated discharge tends to occur locally because of the presence of machining dust between the electrode and workpiece. This concentrated discharge has an adverse effect on the surface finish. Also, it creates a big problem, namely a bridging contact is generated between parts. In order to avoid generating such a concentrated discharge or abnormal discharge, it is necessary to disperse the discharge appropriately. In this study, we investigate EDM characteristics by using assisted ultrasonic vibration of the tool electrode as a method of overcoming the problem. The result showed that the machining speed was increased several times by using assisted ultrasonic vibration of the tool electrode. The method proved to remarkably effective in increasing machining speed even if the amplitude of the ultrasonic vibration was 1 μm. Furthermore, the rate of normal discharge increased by applying ultrasonic vibration. In particular, this method yielded a beneficial effect in finishing conditions. This is expected to produce a better effect under conditions of finish machining when there is a small gap between the electrode and workpiece. In particular, occurrences of abnormal discharges, such as a concentrated discharge, decreased since the electrode tool was forcibly separated from the workpiece. Machining wastes are positively removed as a result of the tool electrode working with a “pumping action.” In particular, when applied to deep-hole machining, this method is extremely effective in machining deeper holes. [ABSTRACT FROM AUTHOR]

Ni-Al 2 O 3 functionally graded materials (FGMs) have become important for high temperature applications due to a continuous change in composition. However, the manufacturing of Ni-Al 2 O 3 FGMs with conventional machining methods is a difficult process because of the high hardness and various graded compositions. In this paper, three-layerd Ni-Al 2 O 3 FGMs, pure Ni layer (100% Ni), 70% Ni/30%Al 2 O 3 layer, 30% Ni/70%Al 2 O 3 layer, have been machined by micro electrical discharge machining (EDM). The machining characteristics of Ni-Al 2 O 3 FGMs have been investigated, which include the effect of open-circuit voltage on material removal rate (MRR), electrical discharge status, surface microtopography, and element distribution. The experimental results indicate that with the increasing open-circuit voltage, the MRR of the pure Ni layer and 70% Ni/30%Al 2 O 3 layer increases slowly and the surface quality becomes worse slowly. In contrast, when open-circuit voltage is changed from 110 to 170 V, the MRR of 30% Ni/70%Al 2 O 3 layer increases rapdily. The surface quality of 30% Ni/70%Al 2 O 3 layer becomes better before getting worse with the increase of open-circuit voltage. In addition, the quantity of normal discharges in the pure Ni layer and 70% Ni/30%Al 2 O 3 layer has a little change, and the quantity of normal discharges in the 30% Ni/70%Al 2 O 3 layer increases rapidly with the increase of open-circuit voltage. Finally, a small hole with fast MRR and good surface quality has been machined suceesfually based on the experimental analysis. [ABSTRACT FROM AUTHOR]

This paper investigates the characteristics of micro electrical discharge machining (EDM) in cold plasma jet using transistor pulse generator. In order to improve the processing efficiency and quality in stable process conditions, oxygen-assisted nitrogen plasma jet, nitrogen-oxygen mixed plasma jet and external compressed air assisted nitrogen plasma jet are used in micro-EDM experiments. It was found that the material removal rate and surface roughness increases with the increase of oxygen flow rate in oxygen-assisted nitrogen plasma jet experiment. In addition, it was found that micro-EDM with a compressed air-assisted plasma jet is superior to oxygen-assisted nitrogen plasma jet in surface quality and edge quality. Nitrogen element is not found on the machined surface in micro-EDM based in NPJ or NJ. The content of oxygen element has an increasing trend when compressed air is used as an auxiliary gas. [ABSTRACT FROM AUTHOR]

Dielectric, such as kerosene-based oil, deionized water or air, is an essential part of electrical discharge machining (EDM). It directly influences machining performance of the EDM process. While there is large tool electrode wear during machining in liquid dielectric, micro EDM in gas dielectric exhibits almost no tool electrode wear. However, small discharge energy, low dynamic viscosity and low debris concentration of micro EDM in gas creates narrow discharge gap, causing frequent occurrence of abnormal discharge. In this paper, nitrogen plasma jet (NPJ) is used as a dielectric to increase the discharge gap of micro EDM in gas. The machining characteristics of micro EDM in NPJ are investigated and compared with those in other dielectrics. It was found that the discharge distance, machining efficiency and surface quality are significantly improved in NPJ, compared to those in gas under the same conditions. The coaxial high-velocity air jet is helpful to reduce short circuits. Experimental results reveal that NPJ is a viable dielectric in micro EDM. [ABSTRACT FROM AUTHOR]

Honeycomb sandwich structure has been widely used in the aerospace industry due to its high strength and stiffness to weight ratio. But the poor machinability of honeycomb core is a key factor that limits its application owing to its weak rigidity in in-plane direction of cellular materials. This paper introduced typical machining defects and studied the machining characteristics of honeycomb core. Almost all the cutting burrs and defects were found to locate on the line with entrance angle is equal to 80° and 170°. A cutting force model was proposed to predict the milling force under different spindle speed, feed rate and tool angle. A series of cutting simulation of honeycomb cell wall with tool blade were conducted to determine the cutting force of a single cell wall. The accuracy of proposed model was verified by a group of experiments under different conditions and the average percentage error is below 5% in Y direction and 10% in X direction. [ABSTRACT FROM AUTHOR]

An ultrahigh voltage is frequently required in electrochemical jet machining (EJM) to produce extreme current densities (>900 A/cm2 for this study) to achieve maximum dissolution rates. However, such a high electric field easily induces a cathodic discharge at the nozzle, and the generation mechanism and characteristics remain unexplored. For the first time, this study shows a direct visualisation of the hydrogen evolution and cathodic discharge in EJM using high-speed photography. An in-depth analysis of the discharge behaviour was carried out based on electrical monitoring, temperature measurement, and characterisation of the resulting changes in the electrode surface. It was revealed that the current density threshold determines the discharge ignition. Discharge occurs preferentially at the inner edge of the nozzle end face, which can cause nozzle wear and reduce localisation of anode workpiece dissolution. The discharge intensity can be controlled by varying the applied voltage and pulse frequency. The electrolyte flow velocity and gap distance influence the discharge behaviour. With appropriate process control, cathodic plasma can enhance the EJM performance while minimising its negative impact. Furthermore, cathodic discharge can be significantly suppressed by designing the geometry of the nozzle tip to avoid local electric field concentration. [Display omitted] • Revealing cathodic phenomena when performing ultra-high current density EJM. • Visualisation of hydrogen evolution, droplet formation and cathodic discharge in EJM. • Demonstration of formation and regulation mechanisms of cathodic plasma. • A mechanistic model describing cathodic discharge and its role in EJM is developed. • The impact of cathodic discharge plasma on EJM performance is presented. [ABSTRACT FROM AUTHOR]

In this study, attempts were made to resolve the problem of unstable discharge at the start of electrical discharge machining using the external superimposition method. In general, electrical discharge machining (EDM), the frontal gap distance is controlled by detecting the working voltage. Electrical discharge machining experiments were thus conducted to compare conventional power supplies for electrical discharge machining machines, which superimpose high voltage on the detected working voltage (internal superimposition) with a power supply that superimposes high voltage externally so that no superimposed voltage is added to the detected working voltage (external superimposition). Differences in abnormal discharge rate, discharge frequency, frontal gap distance, and machining characteristics between the two superimposition methods were also investigated. The results showed that external superimposition is better than internal superimposition in that it widens the frontal gap distance immediately after the start of electrical discharge machining, which decreases the abnormal discharge rate to more or less 0 and increases the discharge frequency in a very short time, and that machining characteristics are better with the external superimposition method. Consequently, the effects of the superimposed voltage level on the machining characteristics of electrical discharge machining applying external superimposition were also investigated. It was found that (1) the discharge frequency increases with increasing superimposition voltage, thereby improving the machining rate; (2) the frontal gap distance increases and the surface roughness of the machined surface improves with increasing superimposition voltage; and (3) the tool electrode wear ratio is the smallest when superimposition voltage is around 200 V. [ABSTRACT FROM AUTHOR]

A nickel-based high-temperature alloy widely used in aerospace engines is a typical difficult-to-cut material by conventional machining processes due to its high-temperature mechanical strength and toughness. Blasting erosion arc machining (BEAM), a new type of electrical discharge machining (EDM) method, is capable of removing such materials with a very high material removal rate and a low tool wear ratio. This paper presents experimental investigations in machining characteristics and machined surface integrity of the nickel-based alloy GH4169 (similar to Inconel718) by positive polarity blasting erosion arc machining (positive BEAM). The test results imply a possibility to improve the surface integrity with positive BEAM compared with a regular negative one. In this work, a three-factor, three-level machining performance experiment was carried out to examine the effects of the machining parameters such as discharge peak current, flushing inlet pressure, and pulse duration on the machining performances of material removal rate, tool wear ratio, and surface roughness. The experimental results show that positive BEAM is capable of greatly improving the machined surface integrity. The surface roughness decreased from 274 μm (under negative polarity BEAM) down to 31 μm (under positive polarity BEAM). Additionally, fewer micro-cracks and a thinner heat-affected zone on the workpiece surface can be observed. It also reveals that by optimizing the combination of the negative and the positive BEAM, favorable machining performances of high material removal rate and finer surface roughness are possible. By utilizing the polarity effects, the machining allowance for the subsequent semi-finishing processes such as cutting can be further reduced. [ABSTRACT FROM AUTHOR]

Aluminium ( Al) alloys are extensively used in all areas of manufacturing including automotive and aerospace industries due to its lightweight, excellent machinability, good surface finish at high cutting speed, low cutting forces and outstanding tool life. Although Al alloys have excellent machinability with conventional machining processes, electric discharge machining (EDM) and micro-EDM are often used to machine intricate features in Al alloys for plastic injection moulds and electronic applications. Present study aims to investigate the influence of various operating parameters on the micro-EDM behaviour of an important Al alloy AA 2024, commonly known as 'Duralumin'. The machining behaviour has been investigated by engraving micro grooves on the surface of the AA 2024 using different parameters settings from a resistance-capacitor (RC) type pulse generator. The operating parameters studied were capacitance, resistance, supply voltage, electrode rotational speed and gap control parameters. The micro-EDM machinability of the AA 2024 alloy was evaluated in terms of the material removal rate (MRR), tool wear ratio (TWR), surface roughness (SR) and machining depth of the micro grooves. It has been found that the increase of capacitance and voltage results in increase of discharge energy, causing higher MRR at the expense of higher tool wear and rougher machined surface. On the other hand, too low capacitance and gap voltage result in unstable machining by creating arcing and short-circuiting, which again makes the surface defective in addition to reducing the machining speed. The careful selection of gap control parameters improves the machining stability by reducing the arcing and short-circuiting as well as improves the overall machining performance. For stable micro-EDM with higher machining speed and improved surface finish, the identification of optimum parameters is needed. With this said, the recommended settings of parameters for micro-EDM of AA 2024 were found to be the voltage of 160 V, capacitance of 10,000 pF and resistance of 470 Ω, spindle speed of 720 rpm, gap feed rate of 0.01 mm/s, gap control factor of 50 and gap threshold voltage of 80 %. [ABSTRACT FROM AUTHOR]

Micro EDM technology is widely used in micro hole machining for its small force and high precision. However, the slow machining speed and large tool wear are the two major problems. In this research, a mist nozzle, whose central axis is coaxial with the tool axis, was proposed to evacuate debris from the narrow gap area in micro-EDM for high-aspect-ratio holes and to improve the machining speed and accuracy. In order to verify the effectiveness of the mist nozzle, experiments by supplying mist jet and water jet, and by changing the flow rate of deionized water were carried out. By comparing the machining results of micro hole drilling with mist jet and water jet, the effectiveness of the mist nozzle was confirmed. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is the extensively used nonconventional material removal process for machining engineering ceramics provided they are electrically conductive. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics that can be machined effectively by EDM. This paper investigates the effects of the electrical resistivity and the EDM parameters on the EDM performance of ZnO/AlO ceramic in terms of the machining efficiency and the quality. The experimental results showed that the electrical resistivity and the EDM parameters such as pulse on-time, pulse off-time, and peak current had the great influence on the machining efficiency and the quality during electrical discharge machining of ZnO/AlO ceramic. Moreover, the electrical resistivity of the ZnO/AlO ceramic, which could be effectively machined by EDM, increased with increasing the pulse on-time and peak current and with decreasing the pulse off-time, respectively. Furthermore, the ZnO/AlO ceramic with the electrical resistivity up to 3,410 Ω cm could be effectively machined by EDM with the appropriate machining condition. [ABSTRACT FROM AUTHOR]