Non-conventional Machining Process Research Articles

Experimental investigation on electric discharge-assisted surface modification of Ti6Al4V with comparative analysis between different polarities in ecofriendly dielectric deionised water

ABSTRACT Electric discharge machining (EDM) is the most widely used non-conventional machining process for machining difficult-to-cut materials in complex geometries and intricate cavities with less cost. The main problem associated with EDMed part is its increased surface roughness (SR). This article made an attempt on surface modification of Ti6Al4V by reducing SR with different polarities of EDM in deionised water, an eco-friendly dielectric. Experiments were performed on both straight and reverse polarities in full factorial with varying two factors (voltage and current) in two levels. The substrate processed with the reverse polarity possesses minimum (1.26 µm) SR of about 2.15 times than that of the straight polarity (2.64 µm) at the parametric conditions of 60 V, 10 A and 100 µs. Enhanced microhardness (300–450 HV1) and specific wear rate (2.4 × 10−4 mm3/Nm) were observed with the straight polarity due to the microstructural changes along with higher SR and defects. Contact angle analysis reveals that both straight and reverse polarity processed parts are hydrophilic in nature. Reverse polarity can be used as an effective tool for surface modification with less SR and defects and with slight increase in microhardness (300–400 HV1) and specific wear rate (2.6 × 10−4 mm3/Nm). The presence of enriched titanium oxide (rutile) observed on the reverse polarity surface increases its applicability, especially in biomedical industries.

A Concise Review on Materials for Injection Moulds and Their Conventional and Non-Conventional Machining Processes

Injection moulds are crucial to produce plastic and lightweight metal components. One primary associated challenge is that these may suffer from different types of failures, such as wear and/or cracking, due to the extreme temperatures (T), thermal cycles, and pressures involved in the production process. According to the intended geometry and respective needs, mould manufacturing can be performed with conventional or non-conventional processes. This work focuses on three foremost alloys: AMPCO® (CuBe alloy), INVAR-36® (Fe-Ni alloys, Fe-Ni36), and heat-treated (HT) steels. An insight into the manufacturing processes’ limitations of these kinds of materials will be made, and solutions for more effective machining will be presented by reviewing other published works from the last decade. The main objective is to provide a concise and comprehensive review of the most recent investigations of these alloys’ manufacturing processes and present the machinability challenges from other authors, discovering the prospects for future work and contributing to the endeavours of the injection mould industry. This review highlighted the imperative for more extensive research and development in targeted domains.

An Extensive Review of Various Optimization Techniques for Electric Discharge Machining

In this paper, an investigation of wire and electric discharge machining has been provided. Wider possibilities for the creation of composites and sophisticated materials were made possible by advances in machining science. As research in this area continues, more materials with complicated meteorological structures and strong mechanical resistance capabilities are emerging. Because of the exceptional strength, toughness, and hardness of these materials, advanced machining techniques are replacing traditional machining techniques in this industry. One unique type of advanced machining technique used in this research is electrical discharge machining. It has also been discussed how these machining methods might develop in the future. This paper serves as both a research tool and a step in that direction. The best settings for the processes outlined above will aid in boosting diverse sectors' output. The research on non-conventional machining processes with diverse optimisation strategies is presented in this review. The optimisation techniques taken into account for the current work were Taguchi's, artificial neural networks, particle swarm optimisation, response surface approach, grey connection analysis, and genetic algorithm.

Micro-electrical discharge machining of nitinol alloy using coated electrode and multi-energy field

ABSTRACT Nitinol alloys are widely utilized across various fields owing to their exceptional elasticity and shape memory characteristics. Their low thermal conductivity, high strength, and high toughness pose significant challenges to conventional machining technologies. To address these challenges, several non-conventional machining processes such as electrical discharge machining have been developed. This study introduces an innovative approach that combines the use of insulated coated electrodes with multi-energy field-assisted electrical discharge machining to improve the application of electrical discharge machining in machining deep microporous. We investigated the effects of the insulated electrode and multi-energy field on surface morphology, taper accuracy, diameter cutting, and the thickness of the recast layer in detail. The findings suggest that the insulated coated electrode combined with multi-energy field-assisted electrical discharge machining achieves better taper accuracy and lower diameter cutting, resulting in a smoother surface and a more uniform, thinner recast layer compared to traditional electrical discharge machining.

Experimental study and modeling of laser micro texturing of Nitinol

The unique material properties of Nitinol have led to its extensive use in the biomedical field and microdevices. However, the machining of Nitinol remains a challenge due to its exceptional mechanical properties. This led to the use of a non-conventional machining process, of which laser machining proved to be most suitable and promising due to its versatility. To understand the process, the sample was irradiated by a laser beam over a straight line. An analytical model attempts to understand the process and predict the minimum process parameters necessary to conduct the machining process. The results are compared experimentally, wherein the influence of laser power and scan speed over the surface morphology, hardness, and groove dimensions are studied in detail. The optimum process signature was 90 W of laser fluence with a 100 mm/s scanning speed.

Parametric assessment of electrical discharge drilling on plasma sprayed functionally graded Al/Al2O3 coating on Al6061-T6 faceplates

Electrical discharge drilling is a non-conventional machining process that is effective and economical for cutting difficult-to-cut conductive materials. In this work, the parametric assessment of functionally graded Al/Al2O3 coating sprayed by plasma on Al6061-T6 faceplates is investigated. Initially, four different graded layers of Al/Al2O3 (50:50, 40:60, 30:70, and 20:80) were processed through plasma spray and deposited coating morphology, splat formation, and cross-sectional structure were confirmed through a scanning electron microscope. The parametric assessment has been investigated based on the effect of electrical discharge drilling parameters peak current (Pc), pulse-on time (Pon), and gap voltage (Vg) on the material removal rate (MRR), tool wear rate (TWR), machining time (MT), surface roughness (SR), taper angle (TA), and overcut (OC). The selected process parameters were Pc from 8 to 14 A, Pon from 60 to 90 μs, and Vg from 20 to 80 V respectively. The parametric assessment was performed based on the objectives of maximizing the MRR and minimizing the TWR, MT, SR, TA, and OC. The effect of process parameters on various output responses was summarized. From the experimentation, MRR is significantly affected by Vg, and maximum MRR is found at the high levels of Pc and Pon. Reduced TWR was observed at the 2nd level of Pc (0.058 mm3 min−1) and 4th level of Vg (0.076 mm3 min−1) and this same factor has more influence on MT. High level of Pc and Pon exhibits maximum TWR with erosion. The results show that Pon time relatively gives low SR (2.36 μm) and minimum OC (0.0015 mm) was achieved at a high level of Vg. Few un-drilled holes with cracks were witnessed due to high TWR. Many drilled holes exhibit < 2° of TA which indicates good dimensional accuracy.

Residual stress, fatigue behavior, and mechanical properties of equal-channel angular pressed commercial pure titanium

Residual stresses, fatigue behavior, and mechanical properties of equal channel angular pressing (ECAP) commercial pure titanium (CP–Ti) are investigated in this study. Residual stresses can significantly affect the performance and reliability of CP-Ti components under cyclic loading conditions. The study focuses on understanding the relationship between ECAP processing, residual stresses, and fatigue behavior in CP-Ti. The ECAP process was employed to produce CP-Ti grade 2 samples, and their fatigue behavior was characterized. The results revealed a significant increment in residual stresses, fatigue strength, microhardness, and tensile strength by ECAP processing on the CP-Ti. The measured fatigue limit of the processed CP-Ti was found to be higher than that of coarse-grained CP-Ti and approaches the fatigue limit of the Ti–6Al–4V alloy. Residual stresses resulting from non-conventional machining processes and surface treatments are known to affect the fatigue life of titanium alloys. Compressive residual stresses have been shown to inhibit the growth rate of fatigue cracks and improve fatigue life. Understanding the effect of residual stresses on the fatigue behavior and mechanical properties of ECAP-processed CP-Ti is crucial to optimizing the design and ensuring the long-term durability of CP-Ti components in engineering applications.

A Statistical and Optimization Study on the Influence of Different Abrasive Types on Kerf Quality and Productivity during Abrasive Waterjet (AWJ) Milling of Ti-4Al-6V.

Non-conventional machining processes offer significant advantages over conventional ones, especially in terms of the productivity, cost, and surface integrity of the produced parts due to their higher flexibility. Abrasive waterjet machining, in particular, constitutes an ecologically friendly process with a negligible thermal impact on a workpiece, and it has considerable capabilities for obtaining the desired outcome by regulating some of its numerous parameters. Among these parameters, the abrasive type is particularly important due to its hardness, mesh size, and shape, which lead to considerable deviations on the obtained depth, kerf characteristics, and productivity. Thus, in this work, a comprehensive comparison is conducted on the use of garnet and silicon carbide particles for the slot milling of the Ti-6Al-4V alloy under different conditions. The capabilities of both abrasive materials are evaluated by statistical analysis regarding the depth of penetration, kerf width, kerf taper angle, and material removal rate (MRR), which are obtained under the same process conditions. Finally, a multi-objective optimization based on grey relational analysis (GRA) is performed for several different practical cases. It was found that, although silicon carbide is more efficient in optimizing individual process outputs, the use of a garnet abrasive can lead to considerably better trade-offs between two or more objectives of the machining process.

Optimal conventional and nonconventional machining processes via particle swarm optimization and flower pollination algorithm

Optimal conventional and nonconventional machining processes via particle swarm optimization and flower pollination algorithm

Laser Beam Machining: A Review on Research Trend

Abstract: Laser Beam Machining (LBM) is an advanced non-conventional machining process that employs a highly focused laser beam to remove material from a work-piece. This thermal-based process utilizes the intense energy of the laser beam to induce localized melting, vaporization, or ablation of the material, resulting in precise and controlled material removal. The process involves key components such as a laser source, optics for beam focusing, and a work-piece mounted in the machining setup. Laser beam machining offers various advantages, including high precision, non-contact nature, minimal heat-affected zone, and the capability to work with a diverse range of materials. The two primary applications of LBM are laser cutting and laser drilling. Laser cutting involves using the laser beam to cut through materials along a specified path, while laser drilling creates holes or openings in the work-piece with great accuracy. The versatility and efficiency of laser beam machining make it suitable for numerous industries, including aerospace, automotive, electronics, medical, and jewellery manufacturing. As a result of its unique capabilities and benefits, LBM continues to play a crucial role in modern manufacturing, enabling the production of intricate and complex components with high precision and quality

Influence of wire-electric discharge machining process parameters on surface integrity of Ni-rich Ni-Ti-Hf alloys

Ni-Ti-Hf Shape memory alloys (SMAs) have shown promising results in high-temperature applications in aviation, space and energy exploration, actuators, etc. In the past decade, extensive work has been carried out to understand the behavior of High-Temperature SMAs (HTSMAs). NiTi-based SMAs are grouped as hard-to-machine materials, and machining these materials through traditional methods leads to high tool wear, dimensional inaccuracy, degradation of Shape Memory properties, etc. Therefore, Non-Conventional machining processes are a better choice for machining these alloys. It is evident from previous studies that Wire Electric Discharge Machining (WEDM) yields better results compared to other processes. The current study investigates the effect of WEDM input variables such as servo gap voltage (SV), spark-ON duration (TON), wire electrode feed rate (WF), and spark-OFF duration (TOFF) on the machining of Ni-Ti-Hf HTMSAs. The surface integrity of the machined samples was analyzed by investigating characteristics like machined surface morphology, machined surface quality, subsurface microhardness, and recast layer thickness. TON emerged as the most critical parameter for surface roughness and Material Removal Rate. Various defects like micro-cracks, micro-pores, craters, and globules were found on the machined surfaces, and approximately 30% harder surface was found near the machined region. The average thickness of the recast layer observed for Hf-15 and Hf-20 samples was around 12 μm and 50 μm for samples with lower and higher discharge energies, respectively.

Kerf Geometry and Surface Roughness Optimization in CO2 Laser Processing of FFF Plates Utilizing Neural Networks and Genetic Algorithms Approaches

This work deals with the experimental investigation and multi-objective optimization of mean kerf angle (A) and mean surface roughness (Ra) in laser cutting (LC) fused filament fabrication (FFF) 3D-printed (3DP), 4 mm-thick polylactic acid (PLA) plates by considering laser feed (F) and power (P) as the independent control parameters. A CO2 laser apparatus was employed to conduct machining experiments on 27 rectangular workpieces. An experimental design approach was adopted to establish the runs according to full-combinatorial design with three repetitions, resulting in 27 independent experiments. A customized response surface experiment was formulated to proceed with regression equations to predict the responses and examine the solution domain continuously. After examining the impact of F and P on mean A and mean Ra, two reliable prediction models were generated to model the process. Furthermore, since LC is a highly intricate, non-conventional machining process and its control variables affect the responses in a nonlinear manner, A and Ra were also predicted using an artificial neural network (NN), while its resulting performance was compared to the predictive regression models. Finally, the regression models served as objective functions for optimizing the responses with an intelligent algorithm adopted from the literature.

IMPROVEMENT OF SURFACE QUALITY OF Ti-6Al-4V ALLOY BY POWDER MIXED ELECTRICAL DISCHARGE MACHINING USING COPPER POWDER

Electrical Discharge Machining (EDM) is one of the most popular non-conventional machining processes that are being used in many high precision manufacturing industries. To increase the EDM performance, a hybrid technique, namely, powder mixed electrical discharge machining (EDM) (PMEDM) is generally used for getting more precise requirements. In this study, an experimental investigation is carried out in order to explore the machining performance of the PMEDM process on Ti-6Al-4V alloy using copper (Cu) powder in the EDM oil dielectric. Taguchi’s L18 orthogonal array design has been utilized for design of experiments and the analysis of variance (ANOVA) has been performed with the help of Minitab-19 software. The optimal parametric setting of Cu powder mixed EDM has been found utilizing the Taguchi - Grey Relational Analysis (GRA) integrated approach and also validation of optimal parametric setting is done through experimentation. It is a novel approach for machining Ti-6Al-4V alloy by this PMEDM technique in which the surface quality has been improved significantly with the addition of suitable amount of Cu powder into the dielectric medium.

Development of AHP-embedded Deng’s hybrid MCDM model in micro-EDM using carbon-coated electrode

Abstract The use of thin film-coated micro-tool electrode introduced a new technical solution to bring the best technical–economic efficiency in the field of non-conventional machining processes. Multi-objective optimization of process parameters in micro-electrical discharge machining (EDM) is very limited with the help of thin film-coated micro-tool, which brought benefits for the industry. In this research work, the technological parameters such as voltage (V), spindle rotation, and capacitance (C) in micro-EDM using carbon-coated electrode were optimized, and Z-coordinate depth of cut and tool wear rate were selected as response variables. Taguchi is combined with Deng’s method to solve this multi-objective decision problem. The results showed that Taguchi–Deng’s method is the right solution for multi-target decision in micro-EDM using the coated electrode. C is the strongest influence on optimal efficiency, and it is the smallest with V. The machining quality under optimal conditions is improved.

Effect of Process Parameters on Material Removal Rate and Surface Characteristics in WEDM Machining of Titanium Grade 7 Alloy

Wire Electrical Discharge Machining (WEDM) is a modern machining technique. WEDM is electro-thermal non-conventional machining processes follow to cut very hard materials. WEDM is non-traditional material cutting operation employed to machine complex geometries and shapes. The present paper attempts to study surface and sub-surface variations during WEDM of titanium grade 7 alloy with Brass wire coated with Zn. This paper presents experimental studies with varying three key process parameters viz. pulse ON time (TON), pulse OFF time (TOFF), peak current (IP). The investigation is focused on assessment of material removal rate, surface roughness as well as recast layer. Scanning electron Microscope (SEM) examinations are carried out on surface textures and are discussed in the article. The obtained results indicated that the stretched pulse time discharges more energy causes rough surface finish. The MRR is also strongly influenced by TON.

Investigations on the Surface Integrity of Ti6Al4V under Modified Dielectric(s)-Based Electric Discharge Machining Using Cryogenically Treated Electrodes

The surface integrity of machined components is considered to be an important part of the quality matrix for high-performance applications in the aviation industry. Therefore, close attention is given to the components made up of hard-to-cut materials such as Ti6Al4V, which face processability challenges. In this regard, among the non-conventional machining processes, electric discharge machining is widely preferred for cutting Ti6Al4V. In this study, the potentiality of cryogenic-treated tool electrodes (graphite and aluminum) with unmodified (kerosene) and modified (kerosene with Span 20, Span 60, and Span 80) dielectrics are comprehensively investigated. A three-phased experimentation framework is deployed based on the following process parameters, i.e., surfactant type, surfactant concentration, electrode material, and pulse ON:OFF time. Thorough statistical analyses are performed based on the full factorial design of experiments, and the results are characterized by process physics. It is found that the cutting mechanism is highly dependent on the surfactants, especially their hydrophilic–lipophilic balance in the dielectric. The desirability-based process optimization results show that the unmodified process (with kerosene) produced relatively higher roughness values of 7.5 µm and 5.8 µm for aluminum and graphite electrodes, respectively. However, the modified process (with surfactant) resulted in a lower degree of roughness on the workpiece. The graphite electrode using S-60 with a resulting Ra of 1.73 µm outperformed the aluminum electrode using S-20, yielding an Ra of 3.4 µm. The S-60 surfactant resulted in minimum roughness on the workpiece with the fewest surface defects at the 25 g/L concentration, 50:25 µSec pulse ON:OFF time, and with the cryogenically treated graphite electrode.

Evaluation of the Machinability of Ti-6Al-4V Titanium Alloy by AWJM Using a Multipass Strategy

Non-conventional machining processes offer various advantages, including the capability of processing hard-to-cut materials with a reasonable cost and sufficient productivity. However, depending on the application, different machining strategies need to be employed, in order to increase the flexibility of the process and produce parts with a better quality. In this study, experimental work was conducted and the use of a multipass strategy during slot milling of titanium alloy with abrasive water jet milling (AWJM) was explored, by comparing the effect of different numbers of passes under different process conditions, such as the jet pressure and traverse feed rate. The performance was evaluated by means of the kerf characteristics, and the productivity through material removal rate (MRR) values. The results indicated that the use of a multipass strategy had a considerable impact on the kerf taper angle, apart from the depth of penetration; and although it leads to reduced MRR and cutting efficiency, choosing appropriate values of process parameters, such as a higher jet pressure and moderate traverse feed, in combination with a moderate amount of passes, can be beneficial for AWJM from different points of view.

Modelling of micro-electrochemical machining parameters used for machining of holes on copper plate

The electrochemical machining is a non-conventional machining process based on the electrolysis principle. It is used to machine various features on conducting engineering materials with the required accuracy and precision. So an attempt has been made to machine micro-holes on a 300 μm thick copper plate as an anode and a hollow stainless steel tool electrode of 250 μm diameter as the cathode. The machining operation is performed on the in-house developed micro-ECM experimental setup with controlled machining parameters voltage, concentration, and duty factor varied in three levels. A full factorial experimental plan is used to study the output responses material removal rate (MRR), radial overcut (ROC), circularity, and taper angle (TA). Later an adaptive neuro-fuzzy inference system (ANFIS) model has been developed and shown the effectiveness of the developed model in the paper. The Sugeno fuzzy model has been used in ANFIS to generate the fuzzy rules required for the model. Out of 27 experiments, 22 machining data are used for training the model, and the remaining 5 machining data are used for testing the developed model. The average error observed between the ANFIS predicted values and experimental values of MRR is 12.56%, circularity is 43.09%, ROC is 13%, and TA is 27.53%, respectively.

Investigation of the material removal rate on haste alloy C-276 using electrical discharge machining

The non-conventional machining processes have better in specific performance i.e., surface finishing, material removal and many more compare to conventional machining processes. Among the all-unconventional machining methods electric discharge machining is widely used in industries for the production of complex shape. Therefore, these machining considerations should be optimized to achieve the desire quality of workpiece at minimum machining cost. The main objective of work is to investigation of the consequence of Electric Discharge Machining (EDM) parameters (current, voltage and, pulse on time) on metal removal rate. The level values for current voltage are selected 10, 20 and 30 V. The level values for current are 2, 6 and 10 Amp. The pulse on time level values is 5, 10 and 15 micro-sec. The material removal rate has been identified for the designed of experiments. The maximum metal removal rate was 53.70 mg/min observed for the higher level (10 Amp.) of peak current, lower level of voltage (10 V) and higher level (15 micro-sec.) of pulse on time designed level.

Design of Real-Time Extremum-Seeking Controller-Based Modelling for Optimizing MRR in Low Power EDM

Electric discharge machining (EDM) is one of the non-conventional machining processes that supports machining for high-strength and wear-resistant materials. It is a challenging task to select the process parameters in real-time to maximize the material removal rate since real-time process trials are expensive and the EDM process is stochastic. For the ease of finding process parameters, a modelling of the EDM process is proposed. Due to the non-linear relationship between the material removal rate (MRR) and discharge time, a model-free adaptive extremum-seeking controller (ESC) is proposed in the feedback path of the EDM process for finding an optimal value of the discharge time at which the maximum material removal rate can be achieved. The results of the model show a performance that is closer to the actual process by choosing steel workpieces and copper electrodes. The proposed model offers a lower error rate when compared with actual experimental process data. When compared to manual searching for an optimal point, extreme seeking online searching performed better as per the experimental results. It was observed that the experimental validation also proved that the ESC can produce a large MRR by tracking the extremum control. The present study has been limited to only the MRR, but it is also possible to implement such algorithms for more than one response parameter optimization in future studies. In such cases the performance measures of the process could be further enhanced, which could be used for a real-time complex die- and mold-making process using EDM.