The effect of electrolyte current density on the electrochemical machining S-03 material

Selecting an appropriate electrolyte is very important for high-efficiency electrochemical machining novel S-03 special stainless steel aerospace component. A series of experiments were conducted with NaCl, NaNO₃, and their admixture solutions. This research focused on the relationship between current efficiency and current density. The current density effects on surface roughness, machining velocity, and grain boundary corrosion were analyzed. The results showed that: the current efficiency in NaCl electrolyte was 100 % with different concentrations. Under the conditions of 24 V voltage, 30 °C electrolyte, and 0.8 MPa electrolyte pressure, the 10 % NaCl electrolyte can obtain 3.6 mm/min cathode feed speed; the surface roughness is Ra 0.08 μm; and the material removal rate is 411.4 mm³/min. Comparing forward flow to forward flow with added backpressure, we found that: the surface roughness value decreased sharply at 3.6 mm/min in NaCl electrolyte.     

An experimental investigation on machining parameters of AISI D2 steel using WEDM

The performance of the wire electrodischarge machining (WEDM) machining process largely depends upon the selection of the appropriate machining variables. Optimization is one of the techniques used in manufacturing sectors to arrive for the best manufacturing conditions, which are essential for industries toward manufacturing of quality products at lowest cost. As there are many process variables involved in the WEDM machining process, it is difficult to choose a proper combination of these process variables in order to maximize material removal rate and to minimize tool wear and surface roughness. The objective of the this work is to investigate the effects of process variables like pulse on time, pulse off time, peak current, servo voltage, and wire feed on material removal rate (MRR), surface roughness (SR), gap voltage, gap current, and cutting rate in the WEDM machining process. The experiment has been done using Taguchi’s orthogonal array L27 (3⁵). Each experiment was conducted under different conditions of input parameters and statistically evaluated the experimental data by analysis of variance (ANOVA) using MINITAB and Design Expert tools. The present work also aims to develop mathematical models for correlating the inter-relationships of various WEDM machining parameters and performance parameters of machining on AISI D2 steel material using response surface methodology (RSM).The significant machining parameters and the optimal combination levels of machining parameters associated with performance parameters were also drawn. The observed optimal process parameter settings based on composite desirability (61.4 %) are pulse on time 112.66 μs, pulse off time 45 μs, spark gap voltage 46.95 V, wire feed 2 mm/min, peak current of 99.99 A for achieving maximum MRR, gap current, gap voltage, cutting rate, and minimum SR; finally, the results were experimentally verified.     

Optimization of machining parameters in the abrasive waterjet turning of alumina ceramic based on the response surface methodology

A study on the radial-mode abrasive waterjet turning (AWJT) of 96 % alumina ceramic is presented and discussed. An experimental investigation is carried out to explore the influence of process parameters (including water pressure, jet feed speed, abrasive mass flow rate, surface speed, and nozzle tilted angle) on the material removal rate (MRR) when turning 96 % alumina ceramic. The experiments are conducted on the basis of response surface methodology (RSM) and sequential approach using face-centered central composite design. The quadratic model of RSM associated with the sequential approximation optimization (SAO) method is used to find optimum values of process parameters in terms of surface roughness and MRR. The results show that the MRR is influenced principally by the water pressure P and the next is abrasive mass flow rate m _a . The optimization results show that the MRR can be improved without increasing the surface roughness when machining 96 % alumina ceramic in the radial-mode abrasive waterjet turning process.     

Investigations on precision finishing of space curve meshing wheel by electrochemical brushing process

In this study, a novel finishing process named electrochemical brushing (ECB) is proposed, which integrates the merits of electrochemical polishing (ECP) and mechanical finishing (MF). It executes finishing for the space curve meshing wheel (SCMW), which was manufactured by the selective laser melting (SLM) rapid prototyping process. First, finishing experiments of ECP and ECB were carried out with optimal parameters, including an applied voltage of 10 V, a cathode and workpiece gap of 1 mm, and an ingredient electrolyte of NaNO₃ (10 %)?+?Al₂O₃ (0.1 %)?+?H₂O. Advantages of the ECB process were shown by analyzing the machining mechanism and comparing the experimental results. Furthermore, the cathode tools and finishing experimental rigs were designed to process SCMW samples. Finally, kinematics experiments were carried out, and the relation between the transmission ratio and the surface roughness of meshing tines is discussed. After ECB, as the surface roughness of meshing tines was reduced from 34 to 0.5 μm, the average transmission ratio of SCMW samples was improved from 3.922 to 3.993 and approached the theoretical value of 4, and its standard deviation was improved from 0.0317 to 0.0077. Therefore, the ECB process could be a feasible process to finish the SCMW to be able to perform precision meshing transmission.     

Experiment and simulation study on concentrated magnetic field-assisted ECM S-03 special stainless steel complex cavity

A novel concentrated magnetic field-assisted electrochemical machining (ECM) technology is proposed in this paper to machine contemporaneously seven workplaces’ complex cavity with high efficiency and good precision. An ECM clamping apparatus with concentrated magnetic field, periodic magnetic field, and no magnetic field was designed. The magnetic field simulation was carried out. Comparing the results of the concentrated magnetic field to the periodic magnetic field, the magnetic field intensity of the former is increased by 9.8 % than the latter. The ECM cathode with the same gap was designed and manufactured. Under the conditions of 12 % NaNO₃, 14-V voltage, 0.8-MPa electrolyte pressure, temperature 32 °C, cathode feed rate 0.9 mm/min, initial machining gap 0.1 mm, and the S-03 special stainless steel workpiece material, the experiments with concentrated magnetic field, periodic magnetic field, and no magnetic field were carried out. The results show that the gap magnetic field strength was increased by 16.7 % in the concentrated magnetic field than in the periodic magnetic field. Through a sectioning test, the precision in the concentrated magnetic field is increased by 33.3 % compared with no magnetic circuit and increased by 14.8 % compared with the periodic magnetic field. The concentrated magnetic field-assisted ECM technology cannot only reduce the cathode design cycle and cost but also increase the process accuracy.     

Investigation into fabrication of microslot arrays by electrochemical micromachining

Maskless electrochemical micromachining (EMM) is a prominent and unique surface texturing method to fabricate the arrays of microslots. This article investigates the generation of microslot arrays using maskless EMM method. The developed prototype maskless EMM setup consists of EMM cell, power supply connections, electrode holding devices and constricted vertical cross flow electrolyte system for the fabrication of microslot arrays economically. One textured cathode tool with SU-8 2150 mask is used to produce 22 microslot arrays. Influences of EMM process parameters including voltage, electrolyte concentration, inter electrode gap, flow rate and machining time on the machining performance that is, width overcut, depth and surface roughness (R_a) of microslot arrays are investigated. For lower width overcut, controlled depth, and lower surface roughness, machining with lower voltage, lower electrolyte concentration, lower inter electrode gap, higher flow rate and lower machining time are recommended. From the analysis, it is observed that the best machining conditions including inter electrode gap of 50?μm, applied voltage of 6 V, electrolyte concentration of 20?g L^?1, flow rate of 5.35 m³ hr^?1 and machining time of 1?min fabricate regular microslot array with mean width overcut of 24.321?μm, mean machining depth of 10.7?μm and mean surface roughness of 0.0101?μm.     

Investigations on the effects of Nano-fluid in ECM of die steel

Formation of spikes in the electrochemically machined workpiece prevents to achieve the better performance of ElectroChemical Machining (ECM). Hence, this research work attempts to investigate the effects of Nano-fluid i.e. Nano Copper particles suspended NaCl electrolyte on the ECM of High carbon high chromium (HCHCr) die steel with a hardness of 63HRc. The influencing parameters are voltage, tool feed rate and electrolyte discharge rate with mixing levels. Seventy-two experiments have been conducted using Nano-fluid and plain NaCl electrolyte based on design of the experiment. The Nano Copper particles in the electrolyte break the gas layer at the inter electrode gap resulting in better MRR and surface roughness due to improved current density across the gap. A maximum MRR of 458.869 mm³/min and a minimum surface roughness of 1.39 μm Ra are obtained using Nano-fluid. The developed ANOVA models prove the significances of influencing factors in obtaining the better performance of ECM.     

Effect of machining parameters on surface roughness and tool wear for 7075 Al alloy SiC composite

In the present study, an attempt has been made to investigate the influence of cutting speed, depth of cut, and feed rate on surface roughness during machining of 7075 Al alloy and 10 wt.% SiC particulate metal-matrix composites. The experiments were conducted on a CNC Turning Machine using tungsten carbide and polycrystalline diamond (PCD) inserts. Surface roughness of 7075Al alloy with 10 wt.% SiC composite during machining by tungsten carbide tool was found to be lower in the feed range of 0.1 to 0.3 mm/rev and depth of cut (DOC) range of 0.5 to 1.5 mm as compared to surface roughness at other process parameters considered. Above cutting speed of 220 m/min surface roughness of SiC composite during machining by PCD tool was less as compared to surface roughness at other values of cutting speed considered. Wear of tungsten carbide and PCD inserts was analyzed using a metallurgical microscope and scanning electron microscope. Flanks wear of carbide tool increased by a factor of 2.4 with the increase of cutting speed from 180 to 240 m/min at a feed of 0.1 mm/rev and a DOC of 0.5 mm. On the other hand, flanks wear of PCD insert increased by only a factor of 1.3 with the increase of cutting speed from 180 to 240 m/min at feed of 0.1 mm/rev and DOC 0.5 mm.     

Optimizing machining parameters of silicon carbide ceramics with ED milling and mechanical grinding combined process

A novel combined process of machining silicon carbide (SiC) ceramics with electrical discharge milling and mechanical grinding is presented. The process is able to effectively machine a large surface area on SiC ceramics with a good surface quality. The effect of tool polarity on the process performance has been investigated. The effects of peak current, peak voltage, pulse on-time and pulse off-time on the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR) have been investigated with Taguchi experimental design. The mathematical models for the MRR, EWR, and SR have been established with the stepwise regression method. The experiment results show that the MRR, EWR, and SR can reach 46.2543 mm³/min, 20.7176%, and 0.0340 µm, respectively, with each optimal combination level of machining parameters.     

Taguchi analysis of drilling quality associated with core drill in drilling of composite material

The thrust force and surface roughness of core drill with drill parameters (grit size of diamond, thickness, feed rate and spindle speed) in drilling carbon fiber reinforced plastic (CFRP) laminate was experimentally investigated in this study. A L₂₇ (3¹³) orthogonal array and signal-to-noise (S/N) were employed to analyze the effect of drill parameters. Using Taguchi method for design of a robust experiment, the interactions among factors are also investigated. The experimental results indicate that thickness and feed rate are recognized to make the most significant contribution to the overall performance. For thrust force, the drilling conditions were A₁B₁C₁D₂, (i.e., grit size of diamond=#60, thickness=1.0 mm, feed rate=0.012 mm/rev, and spindle speed=950 rpm). For surface roughness, the drilling conditions were A₁B₁C₁D₃, (i.e., grit size of diamond=#60, thickness=1.0 mm, feed rate=0.012 mm/rev, and spindle speed=1150 rpm). The correlation was obtained by multi-variable nonlinear regression and compared with the experimental results. The confirmation tests demonstrated a feasible and an effective method for the evaluation of drilling-induced thrust force and surface roughness (errors within 10%) in drilling of composite material.     

Application of adaptive neuro-fuzzy inference system and cuckoo optimization algorithm for analyzing electro chemical machining process

Electrochemical machining process (ECM) is increasing its importance due to some of the specific advantages which can be exploited during machining operation. The process offers several special privileges such as higher machining rate, better accuracy and control, and wider range of materials that can be machined. Contribution of too many predominate parameters in the process, makes its prediction and selection of optimal values really complex, especially while the process is programmized for machining of hard materials. In the present work in order to investigate effects of electrolyte concentration, electrolyte flow rate, applied voltage and feed rate on material removal rate (MRR) and surface roughness (SR) the adaptive neuro-fuzzy inference systems (ANFIS) have been used for creation predictive models based on experimental observations. Then the ANFIS 3D surfaces have been plotted for analyzing effects of process parameters on MRR and SR. Finally, the cuckoo optimization algorithm (COA) was used for selection solutions in which the process reaches maximum material removal rate and minimum surface roughness simultaneously. Results indicated that the ANFIS technique has superiority in modeling of MRR and SR with high prediction accuracy. Also, results obtained while applying of COA have been compared with those derived from confirmatory experiments which validate the applicability and suitability of the proposed techniques in enhancing the performance of ECM process.     

Soft computing models based prediction of cutting speed and surface roughness in wire electro-discharge machining of tungsten carbide cobalt composite

This paper reports on an experimental investigation of small deep hole drilling of Inconel 718 using the EDM process. The parameters such as peak current, pulse on-time, duty factor and electrode speed were chosen to study the machining characteristics. An electrolytic copper tube of 3 mm diameter was selected as a tool electrode. The experiments were planned using central composite design (CCD) procedure. The output responses measured were material removal rate (MRR) and depth averaged surface roughness (DASR). Mathematical models were derived for the above responses using response surface methodology (RSM). The results revealed that MRR is more influenced by peak current, duty factor and electrode rotation, whereas DASR is strongly influenced by peak current and pulse on-time. Finally, the parameters were optimized for maximum MRR with the desired surface roughness value using desirability function approach.     

Grinding-aided electrochemical discharge machining of particulate reinforced metal matrix composites

A grinding-aided electrochemical discharge machining (G-ECDM) process has been developed to improve the performance of the conventional ECDM process in machining particulate reinforced metal matrix composites (MMCs). The G-ECDM process functions under a combined action of electrochemical dissolution, spark erosion, and direct mechanical grinding. The tool electrode has a coating containing a hard reinforcement phase of diamond particles. The MMC employed in this study was Al₂O₃ particulate reinforced aluminum 6061 alloy. The material removal mechanism of this hybrid process has been analyzed. The results showed that the grinding action can effectively remove re-cast material deposited on the machining surface. The surface roughness (R _a) measured for the G-ECDM specimen was ten times smaller than that of the specimen machined without grinding aid (i.e., ECDM alone). Moreover, the material removal rate (MRR) of G-ECDM was about three times higher than that of ECDM under the experimental conditions of this study. The voltage waveform and crater distribution were also analyzed, and the experimental results showed that the G-ECDM process operates in a stable condition. The relative importance of the various processing parameters on MRR was established using orthogonal analysis. The results showed that MRR is influenced by the machining parameters in the order of duty cycle?>?current?>?electrolyte concentration. This study showed that the G-ECDM process is superior to the ECDM process for machining particulate reinforced MMCs, where a higher machining efficiency and a better surface quality can be obtained.     

A study of die helical thread cavity surface finish made by Cu-W electrodes with planetary EDM

An experimental research study intended for the application of a planetary electrical discharge machining (EDM) process with copper-tungsten (Cu-W) electrodes in the surface micro-finishing of die helical thread cavities made with AISI H13 tool steel full-hardened at 53 HRC is presented. To establish the EDM parameters’ effect on various surface finishing aspects and metallurgical transformations, three tool electrode Cu-W compositions are selected, and operating parameters such as the open-circuit voltage (U ₀), the discharge voltage (u _e), the peak discharge current (î _e), the pulse-on duration (t _i), the duty factor (τ) and the dielectric flushing pressure (p _in), are correlated. The researched machining characteristics are the material removal rate (MRR—V _w), the relative tool wear ratio (TWR—?), the workpiece surface roughness (SR—Ra), the average white layer thickness (WLT—e _wl) and the heat-affected zone (HAZ—Z _ha). An empirical relation between the surface roughness (SR—Ra) and the energy per discharge (W _e) has been determined. It is analysed that copper-tungsten electrodes with negative polarity are appropriate for planetary EDM die steel surface micro-finishing, allowing the attaining of good geometry accuracy and sharp details. For die steel precision EDM, the relative wear ratio optimum condition and minor surface roughness takes place at a gap voltage of 280 V, discharge current of 0.5–1.0 A, pulse-on duration of 0.8 μs, duty factor of 50%, dielectric flushing pressure of 40 kPa and copper tungsten (Cu20W80) as the tool electrode material with negative polarity. The copper-tungsten electrode’s low material removal rate and low tool-wear ratio allows the machining of EDM cavity surfaces with an accurate geometry and a “mirror-like” surface micro-finishing. A planetary EDM application to manufacture helical thread cavities in steel dies for polymer injection is presented. Conclusions are appointed for the planetary EDM of helical thread cavities with Cu-W electrodes validating the accomplishment as a novel technique for manufacturing processes.     

A dual response surface-desirability approach to process modeling and optimization of Al2O3 powder-mixed electrical discharge machining (PMEDM) parameters

This paper presents an effort to model and optimize the process parameters involved in powder-mixed electrical discharge machining (PMEDM). Aluminum oxide (Al₂O₃) fine abrasive powders with particle concentration and size of 2.5–2.8 g/L and 45–50 μm, respectively, were added into the kerosene dielectric liquid of a die-sinking electrical discharge machine. The experiments were carried out in planing mode on a specially designed experimental set up developed in laboratory. The CK45 heat-treated die steel and commercial copper was used as work piece and tool electrode materials, respectively. Response surface methodology, employing a face-centered central composite design scheme, has been used to plan and analyze the experiments. Based on the preliminary and screening tests as well as the working characteristics of selected EDM machine, discharge current (I), pulse-on time (T _on), and source voltage (V) were designated as the independent input variables to assess the process performance in terms of material removal rate (MRR) and surface roughness (Ra). Suitable mathematical models for the response outputs were obtained using the analysis of variance technique, in which significant terms (main effects, two factor interactions, and pure quadratic terms) were chosen according to their p values less than 0.05 (95 % of confidence interval). Having established the suitable regression equations, a search optimization procedure, based on the use of desirability functions, optimizes the process performance in each machining regime of finishing (Ra?≤?3 μm), semifinishing (3 μm?≤?Ra?≤?4.5 μm), and roughing (Ra?≥?4.5 μm). The results are sets of optimum points which make the MRR as high as possible and keep the Ra and all machining parameters in their specified ranges simultaneously. Finally, the modeling and obtained optimization results were also discussed and verified experimentally. It was shown that the error between experimental and anticipated values at the optimal combination settings of input variables are all less than 11 %, confirming the feasibility and effectiveness of the adopted approach.     

Modelling and analysis of hybrid electrochemical turning-magnetic abrasive finishing of 6061 Al/Al2O3 composite

This paper integrates the electrochemical turning (ECT) process and magnetic abrasive finishing (MAF) to produce a combined process that improves the material removal rate (MRR) and reduces surface roughness (SR). The present study emphasizes the features of the development of comprehensive mathematical models based on response surface methodology (RSM) for correlating the interactive and higher-order influences of major machining parameters, i.e. magnetic flux density, applied voltage, tool feed rate and workpiece rotational speed on MRR and SR of 6061 Al/Al₂O₃ (10% wt) composite. The paper also highlights the various test results that also confirm the validity and correctness of the established mathematical models for in-depth analysis of the effects of hybrid ECT- MAF process parameters on metal removal rate and surface roughness. Further, optimal combination of these parameters has been evaluated and it can be used in order to maximize MRR and minimize SR. The results demonstrate that assisting ECT with MAF leads to an increase machining efficiency and resultant surface quality significantly, as compared to that achieved with the traditional ECT of some 147.6% and 33%, respectively.     

Modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al2O3+TiC mixed ceramic

Electric discharge machining (EDM) has achieved remarkable success in the manufacture of conductive ceramic materials for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al₂O₃+TiC mixed ceramic which are developed using the response surface methodology (RSM) to explain the influences of four machining parameters (the discharge current, pulse on time, duty factor and open discharge voltage) on the performance characteristics of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). This study highlights the development of mathematical models for investigating the influences of machining parameters on performance characteristics and the proposed mathematical models in this study have proven to fit and predict values of performance characteristics close to those readings recorded experimentally with a 95% confidence interval. Results show that the main two significant factors on the value of the material removal rate (MRR) are the discharge current and the duty factor. The discharge current and the pulse on time also have statistical significance on both the value of the electrode wear ratio (EWR) and the surface roughness (SR).     

Free abrasive wire saw machining of ceramics

Currently, many kinds of ceramics are used in advanced industrial fields due to their superior mechanical properties, such as thermal, wear, corrosion resistance, and lightweight features. Wire saw machining ceramic (Al₂O₃) was investigated by ultrasonic vibration in this study. Taguchi approach is a powerful design tool for high-quality systems. Material removal rate, wafer surface roughness, steel wire wear, kerf width, and flatness during machining ceramic were selected as quality character factors to optimize the machining parameters (swinging angle, concentration, mixed grain and direction of ultrasonic vibration) to get the larger-the-better (material removal rate) and the smaller-the-better (wafer surface roughness, steel wire wear, kerf width and flatness) machining characteristics by Taguchi method. The results indicated that wire swinging produces a higher material removal rate and good wafer surface roughness. Ultrasonic vibration improved material removal rate, without affecting the flatness under different machining conditions. Experimental results show that the optimal wire saw machining parameters based on grey relational analysis can be determined effectively and material removal rate increases from 2.972 to 3.324 mm²/min, wafer surface roughness decreases from 0.37 to 0.34 μm, steel wire wear decreases from 0.78 to 0.77 μm, kerf width decreases from 0.352 to 0.350 mm, and flatness decreases from 7.51 to 7.22 μm are observed.     

Machinability investigation in hard turning of AISI D3 cold work steel with ceramic tool using response surface methodology

The hard turning process has been attracting interest in different industrial sectors for finishing operations of hard materials. In this paper, the effects of cutting speed, feed rate, and depth of cut on surface roughness, cutting force, specific cutting force, and power in the hard turning were experimentally investigated. An experimental investigation was carried out using ceramic cutting tools, composed approximately with (70 %) of Al₂O₃ and (30 %) of TiC, in surface finish operations on cold work tool steel AISI D3 heat-treated to a hardness of 60 HRC. Based on 3³ full factorial designs, a total of 27 tests were carried out. The range of each parameter is set at three different levels, namely, low, medium, and high. Analysis of variance is used to check the validity of the model. Experimental observations show that higher cutting forces are required for machining harder work material. This cutting force gets affected mostly by feed rate followed by depth of cut. Feed rate is the most influencing factor on surface roughness. Feed rate followed by depth of cut become the most influencing factors on power; especially in case of harder workpiece. Optimum cutting conditions are determined using response surface methodology (RSM) and the desirability function approach. It was found that, the use of lower depth of cut value, higher cutting speed, and by limiting the feed rate to 0.12 and 0.13 mm/rev, while hard turning of AISI D3 hardened steel, respectively, ensures minimum cutting forces and better surface roughness. Higher values of depth of cut are necessary to minimize the specific cutting force.     

Multiple-response optimization for micro-endmilling process using response surface methodology

In the present trend, new fabrication methods for producing miniaturized components are gaining popularity due to the recent advancements in micro-electro mechanical systems. Micro-machining differs from the traditional machining with the small size tool, resolution of x?Cy and z stages. This paper focuses RSM for the multiple response optimization in micro-endmilling operation to achieve maximum metal removal rate (MRR) and minimum surface roughness. In this work, second-order quadratic models were developed for MRR and surface roughness, considering the spindle speed, feed rate and depth of cut as the cutting parameters, using central composite design. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. These optimized machining parameters are validated experimentally, and it is observed that the response values are in good agreement with the predicted values.