Electro-discharge Diamond Grinding Research Articles

ANN-NSGA-II dual approach for modeling and optimization in abrasive mixed electro discharge diamond grinding of Monel K-500

Hybrid machining processes (HMPs) have attracted the attention of investigators from both academia and industry due to their enhanced process performance and capabilities while machining so-called difficult-to-cut materials. In this paper, the dual approach of Artificial Neural Network (ANN) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) was used to model and optimize a new HMP called as Abrasive Mixed Electro Discharge Diamond Grinding (AMEDDG). Due to complex nature of AMEDDG process, the choice of an appropriate coalition of input factors is an effortful job for machinist. The central composite rotatable design was used to plan the experiments and ANN model was established to observe the effect of input machining parameters viz. Wheel speed, powder concentration, pulse current, and pulse-on-time on material removal rate (MRR) and average surface roughness (Ra). The established ANN model was found to be capable of forecasting the output responses within tolerable limits for the chosen set of machining parameters. An ANN-NSGA-II based dual approach was applied for multi-objective optimization of control factors in AMEDDG, and experimental validation directs that optimal data was in tolerable limits.

Application of protective coatings in combined electric diamond grinding

The article discusses the practical use of combined electro-discharge diamond grinding characterized by metal bond grinding wheel operation in a self-sharpening mode with minimal wheel consumption. The upgrading of grinding equipment technological capabilities at processing high-strength materials is possible due to the galvanic deposition of anti-friction and anti-corrosion films on the surfaces of the diamond wheel and the workpiece. These conditions facilitate the cutting process thereby increasing performance and the quality of the processed surfaces of machine parts. The application of this method provides the diamond wheels operation in self-sharpening mode and guarantees the continuity of its geometric shape which in turn ensures that no defective layer is formed on the treated surface and the cutting tools have longer efficient life.

Parametric modeling and optimization for abrasive mixed surface electro discharge diamond grinding of Inconel 718 using response surface methodology

Nickel-based superalloy, Inconel 718, owing to its superior high-temperature strength, excellent fatigue, and corrosion resistance, has been widely used in the aerospace industry. However, there are inherent problems associated with the conventional machining of Inconel 718 superalloy. Therefore, in this work, investigation on machining of Inconel 718 using a hybrid machining process called abrasive mixed surface electro discharge diamond grinding (AMSEDDG) has been presented. In AMSEDDG, abrasive particles are mixed in a dielectric fluid and surface electric discharge diamond grinding (SEDDG) is performed on the workpiece. Preliminary comparative experimentation for AMSEDDG of Inconel 718 resulted in better performance in terms of material removal rate (MRR) and average surface roughness, compared to the performance of electro discharge machining, electro discharge grinding, and SEDDG. The response surface methodology approach has been used for performing and analyzing the experiments to explain the influences of four control factors, including the wheel speed, abrasive concentration, current, and pulse on time, on the performance measures of MRR and average surface roughness. The models established were found to be trustworthy representatives of the experimental results with prediction errors less than ±5%. The results represent that the addition of abrasives in dielectric has a significant effect on both performance measures. The desirability function approach for optimizing the process performance resulted in MRR of 14.45 mm3/min and average surface roughness of 2.621 μm for optimum settings of control factors, viz., wheel speed of 1355 RPM, abrasive concentration of 4 g/L, current of 6 A, and pulse on time of 22 μs.

Artificial neural network–based and response surface methodology–based predictive models for material removal rate and surface roughness during electro-discharge diamond grinding of Inconel 718

Hybrid machining processes growing popularity in the processing of difficult-to-cut materials due to their distinct merits over individual machining processes attributed by an amalgamation of two or more machining mechanisms simultaneously. This research study deals with the response surface methodology and artificial neural network with backpropagation algorithm–based mathematical modeling of electro-discharge diamond grinding of Inconel 718 superalloy. The matrix experiments were designed based on central composite design. The wheel speed, current, pulse-on-time, and duty factor were chosen as control factors, while material removal rate and average surface roughness ( Ra) were chosen as performance parameters. The analysis of variance test shows that the wheel speed is the major factor influencing both the material removal rate and the Ra and contributes 89.03% and 79.10% on material removal rate and Ra, respectively, followed by current which contributes 4.43% and 8.38% on material removal rate and Ra, respectively. The modeling and predictive abilities of developed artificial neural network model (4-24-2) were related to the response surface methodology model using root mean square error and absolute standard deviation. The predicted values of material removal rate and Ra by response surface methodology and artificial neural network are in close agreement with the actual experimental results.

Experimental Investigations of Abrasive Mixed Electro Discharge Diamond Grinding of Nimonic 80A

This paper presents a novel hybrid machining process (HMP) called abrasive mixed electro discharge diamond grinding (AMEDDG) in which abrasive powder is mixed in dielectric fluid to perform electro discharge diamond grinding (EDDG) action on a workpiece. In-house-fabricated AMEDDG setup was used to experimentally evaluate the performance of the process during the machining of Nimonic 80A. The effects of wheel speed, powder concentration, current, and pulse-on-time (POT) were investigated on the material removal rate (MRR). The surface morphological properties of the machined workpiece were investigated based on some quality surface indicators. The experimental results show that MRR of the workpiece was influenced by wheel speed, current, and powder concentration, and optimum MRR can be achieved at a wheel speed of 1400 RPM, a powder concentration of 4 g/L, a current of 10 A, and a POT of 26 µs.

Three dimensional thermal finite element simulation of electro-discharge diamond surface grinding

The key to achieve good surface integrity in the workpiece due to Electro-Discharge Diamond Grinding (EDDG) process, which is hybrid of grinding and EDM, is by preventing the excessive temperature and thermal stress generated during the process. EDDG in surface grinding mode called Electro-Discharge Diamond Surface Grinding (EDDSG), used for finishing operation, is a complex machining process where several disciplines of science and engineering are involved in its theory. The complexity of the process includes the random occurrence of spark during EDM process and nonlinear behavior of workpiece material includes temperature dependent thermal properties. The present work involves the development of a simulation model to simulate the complex EDDSG process which consists of simulation of each constituent process namely EDM and surface grinding for temperature and thermal stress distribution. In order to simulate the realistic complex conditions, the three dimensional FEM is used in the process of development of the model accounting the random occurrence of the spark during EDM. The effect of different dielectric fluid, duty factor and energy partition during EDM on the temperature distribution and MRR study related to EDM contribution are reported. It is observed that the spark contributes primarily to the temperature. The predicted results can be used to determine the surface integrity of the machined surface.

Modelling and optimisation of electro-discharge diamond face grinding of cemented carbide-cobalt composite

Electro-discharge diamond grinding is a hybrid process of electrodischarge machining (EDM) and diamond grinding which is obtained by replacing the tool electrode of conventional EDM by a metal bonded diamond wheel. When face of the wheel is used for machining then the process is termed as electro-discharge diamond face grinding (EDDFG). In this study, modelling and optimisation of EDDFG of cemented carbide–cobalt composite has been done using a hybrid methodology comprising of Taguchi methodology (TM) and response surface methodology (RSM) with material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR) as the objective functions. The approach first uses the TM for finding the optimum level of input machining parameters such as wheel speed, current, pulse on-time and duty factor. The optimum input parameter values are further used as the central values in the RSM to develop second-order response model for MRR, WWR and ASR after conducting experiments using central composite rotatable design matrix. The simultaneous optimisation of weighted response has been obtained using MINITAB software. The results show considerable improvement in three quality characteristics when the hybrid approach is used, as compared with the results of only a TM approach.

Experimental study and parameter optimisation of electro-discharge diamond face grinding

Electro-discharge diamond face grinding (EDDFG), a hybrid machining process comprising diamond face grinding (DFG) and electro-discharge machining (EDM), has been developed for machining of electrically conductive difficult-to-machine very hard materials. The process employs simultaneous synergetic interactive effect of abrasion action and electro-discharge action. A face grinding setup for electro-discharge diamond grinding (EDDG) process is developed. The effect of wheel RPM, current, pulse on-time and duty factor on material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (Ra), while machining high speed steel (HSS) workpiece, are investigated. It is observed that the MRR increase with increasing wheel RPM, current and pulse on-time, while it decreases with an increase in duty factor. The most significant factor affecting the EDDFG robustness has been identified as pulse on-time and duty factor.

Diamond face grinding of WC-Co composite with spark assistance: Experimental study and parameter optimization

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 µs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.

English

Electro-Discharge Diamond Grinding (EDDG), a hybrid machining process comprising diamond grinding and electrodischarge grinding, has been developed for machining of electrically conductive difficult-to-machine very hard materials. The process employs simultaneous synergetic interactive effect of abrasion action and electro-discharge action. A self-designed face grinding setup is attached on ELEKTRA PULS EDM machine to use it as Electro-Discharge Diamond Face Grinding (EDDFG). This paper investigates optimization design of an EDDFG process performed on high speed steel (HSS).The major performance characteristics selected to evaluate the processes are material removal rate (MRR) and wheel wear rate (WWR), and the corresponding EDDFG parameters are wheel RPM, current, pulse ontime and duty factor. In this study, since the process is with multiple-performance characteristics, therefore, the grey relational analysis that uses grey relational grade as performance index is specially adopted to determine the optimal combination of EDDFG parameters. Moreover, the principal component analysis is applied to evaluate the weighting values corresponding to various performance characteristics so that their relative importance can be properly and objectively described. The results of confirmation experiments reveal that grey relational analysis coupled with principal component analysis can effectively be used to obtain the optimal combination of EDDFG parameters. Hence, this confirms that the proposed approach in this study can be a useful tool to improve the machining performance of EDDFG process.

Prediction of wear and surface roughness in electro-discharge diamond grinding

Abstract The present work focuses on prediction of wheel wear and surface roughness using two techniques, namely design of experiments and neural network. Effect of process parameters, such as pulse current, duty ratio, wheel speed and grain size on output responses, namely, wheel wear and surface roughness of high speed steel (HSS) were investigated experimentally.

Experimental study and parameter design of electro-discharge diamond grinding

Electrical discharge diamond grinding (EDDG), which integrates diamond grinding and electro-discharge machining (EDM), is a new hybrid machining process for shaping electrically conductive very hard materials. The process employs synergetic interactive effect of electro-discharge action and abrasion action to increase machining performance. This paper presents an investigation on the experimental study and machining parameter design of electro-discharge diamond grinding (EDDG). The EDDG setup was designed and fabricated, and experiments were conducted on high speed steel (HSS) workpiece under varying current, pulse-ontime, duty factor and wheel speed. The settings of machining parameters were determined by using the Taguchi experimental design method. The level of the machining parameters on the MRR is determined by using analysis of variance (ANOVA). The optimum machining parameter combination was obtained by using the evaluated S/N ratio.

Theoretical Analysis of Thermal Stresses in Electro-discharge Diamond Grinding

Excessive heat generated at the machining zone, during Electro-discharge diamond grinding (EDDG), is the major cause of thermal stresses, untempered martensite, overtempered martensite, and cracks. Therefore, the key to achieve good surface integrity in a machined part is to prevent excessive temperature and thermal stresses generated during machining process. A finite element model has been developed to estimate thermal stresses during EDDG when the current is switched-off. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. Computations were carried out in plane strain condition for different down feeds of the grinding wheel. The effects of time of grinding and feed on thermal stress distribution have been reported. The thermal stresses are found to be higher near top surface at initial time of grinding but shifted away towards bottom after some grinding time.

Parametric Study of Temperature Distribution in Electrodischarge Diamond Grinding

Electrodischarge diamond grinding (EDDG) is a potential process for machining of advance engineering components, but there is no theory to support it. The work reported in this article makes an attempt in this direction. This article reports on determination of temperature distribution in the workpiece due to EDDG using the finite element method. The temperature distribution in the workpiece domain due to EDDG is obtained by superposition of the two temperature distributions for grinding and electrical discharge mechining (EDM) (i.e., 2D for grinding and axisymmetric for EDM). The effects of duty cycle, on-time, current, energy partition, time of machining, and feed velocity while machining are computationally investigated.

On the temperature and specific energy during electrodischarge diamond grinding (EDDG)

Electrodischarge diamond grinding (EDDG) is a hybrid machining process comprising conventional grinding and electrodischarge machining (EDM) as its constituent processes. It has the potential of shaping advanced engineering materials. Temperature of the workpiece and material removal rate are chosen as responses in full factorial (33) design with current, pulse-on time, and wheel speed as process parameters. Specific energy is a vital consideration for any machining process. EDM is known for its inefficiency. Experiments were conducted with a specially fabricated bronze disk as tool electrode to evaluate specific energy in EDM, and the results were compared with that of EDDG. It has been found that specific energy required in EDDG is less than that in EDM with a rotating disk electrode.

Parametric Study of Temperature Distribution in Electrodischarge Diamond Grinding

Abstract Electrodischarge diamond grinding (EDDG) is a potential process for machining of advance engineering components, but there is no theory to support it. The work reported in this article makes an attempt in this direction. This article reports on determination of temperature distribution in the workpiece due to EDDG using the finite element method. The temperature distribution in the workpiece domain due to EDDG is obtained by superposition of the two temperature distributions for grinding and electrical discharge mechining (EDM) (i.e., 2D for grinding and axisymmetric for EDM). The effects of duty cycle, on-time, current, energy partition, time of machining, and feed velocity while machining are computationally investigated.