Neelesh Kumar Jain

Modeling of material removal in mechanical type advanced machining processes: a state-of-art review

Performance of any machining process is evaluated in terms of machining rate and surface finish produced. Higher machining rate and better surface finish are desirable for better performance of any machining process. Comprehensive qualitative and quantitative analysis of the material removal mechanism and subsequently the development of analytical model(s) of material removal (MR) are necessary for a better understanding and to achieve the optimum process performance. Analytical MR models are also necessary for simulation, optimization and planning (i.e. operation and process planning) of the process, prediction of process performance indicators, verification and improvements of experimental results, selection of appropriate models for specific type of work material and machining conditions, etc. Since the inception of different unconventional machining processes, various investigators have proposed different analytical models of material removal as functions of controllable process variables. A continual need for a comprehensive and exhaustive review of various analytical material removal models for different advanced machining processes is being felt. This paper is intended to fulfil this need in the area of advanced machining. Various analytical and some semi-empirical/empirical material removal models (approximately 40) for different mechanical type advanced machining processes have been comprehensively and exhaustively reviewed, and have been presented in a format suitable for quick reference.

Investigations on precision finishing of helical gears by electrochemical honing process

Abstract This paper presents the findings of an investigation into the effects of finishing time, electrolyte-related parameters (i.e. electrolyte temperature, composition, and concentration), voltage, and rotating speed of the workpiece on the improvement of surface quality of helical gear teeth finished by the electrochemical honing (ECH) process. Percentage improvement in average surface roughness PIR a and maximum surface roughness PIR tm, three-dimensional plots of the finished surface texture, and microhardness have been used as the measures of ECH process performance. The effects of finishing time, electrolyte temperature, and electrolyte composition have been studied through pilot experiments by varying one variable at a time, while the effects of voltage, rotating speed of the workpiece gear, and electrolyte concentration have been studied during the main experiments designed using the Box–Behnken response surface methodology approach. Scanning electron microscopy and optical profilometry before and after ECH have been used to highlight the improvement in surface quality of helical gears. A special type of cathode gear has been developed by sandwiching a conducting copper gear between two insulating gears of Bakelite, having the capability of varying the rate of electrolytic dissolution steplessly along the full profile of the workpiece gear made of EN8. Based on the results of pilot experiments, 7.5 min as finishing time, a mixture of NaCl and NaNO3 in a ratio of 3:1, and 32 °C as electrolyte temperature were found to be optimum for precision finishing of helical gears. Using the results of main experiments, regression models have been developed for the measures of process performance (i.e. PIR a and PIR tm). Analysis of variance done at the 95 per cent confidence level, to test the significance of the developed models and process variables, found that the developed models are highly significant and that voltage and electrolyte concentration have significant effects on the responses. However, no significant interaction effect has been observed. Predictions from the regression models have been validated by comparing them with the results of the confirmation experiments, which proved that the developed models are correct and acceptable.

OPTIMIZATION OF ELECTRO-CHEMICAL MACHINING PROCESS PARAMETERS USING GENETIC ALGORITHMS

ECM and ECM-based processes (derived and hybrid processes) are one of the most widely used advanced machining processes (AMPs) to make complicated shapes of varying sizes in the products made of electrically conducting but difficult-to-machine materials such as superalloys, Ti-alloys, alloy steel, tool steel, stainless steel, etc. These materials are extensively used in aerospace, automobile, space, nuclear, defense, cutting tools, dies and mold making applications. ECM offers some unique advantages over other conventional and advanced machining processes but its use incurs relatively higher initial investment cost, operating cost, tooling cost, and maintenance cost. Use of optimum ECM process parameters can significantly reduce the ECM operating, tooling, and maintenance cost and will produce components of higher accuracy which is very important in some critical areas such as aerospace, space, defense, nuclear applications. Therefore, choice of optimum process parameters is essential to ensure the most cost-effective, efficient, and economic utilization of ECM process potentials. This paper describes optimization of three most important ECM process parameters namely tool feed rate, electrolyte flow velocity, and applied voltage with an objective to minimize geometrical inaccuracy subjected to temperature, choking, and passivity constraints using real-coded genetic algorithms. Comparison of the obtained optimization results with the results of past work in this direction shows an improvement in terms of geometrical accuracy.

State-of-art-review of electrochemical honing of internal cylinders and gears

Abstract This paper is an attempt to present a state-of-the-art review of two major applications of electrochemical honing (ECH) for internal cylinders and gears, which are the most commonly used parts in numerous engineering applications. ECH is a hybrid process of electrochemical machining (ECM) and mechanical honing, combining the fast material removal capabilities of ECM and controlled functional surface generating capabilities of mechanical honing in a single operation. ECH is a precision micro-finishing process capable of producing excellent surface quality having a cross-hatch lay pattern required for lubricating oil retention, compressive residual stresses required for the components subjected to cyclic loading, and completely stress-free surfaces. Furthermore, it provides these benefits productively. It makes ECH an ideal choice for superfinishing, improving the surface integrity, and increasing the service life of the critical components such as internal cylinders, transmission gears, carbide bushings and sleeves, rollers, petrochemical reactors, moulds and dies, gun barrels, etc., most of which are made of very hard and/or tough, wear-resistant materials generally susceptible to heat distortions. Consequently, ECH finds widespread use in the automobile, avionics, petrochemical, power generation, and fluid power industries. This paper presents a detailed description of the process principle, parameters, capabilities, equipment details, applications, and comprehensive literature review of past research work on the ECH of internal cylinders and gears along with some directions for future research with an objective to revive the interest of the global research community to mature this process further.

Analysis and optimization of surface finish of wire electrical discharge machined miniature gears

This article reports about analysis and optimization of surface roughness parameters (i.e. average roughness Ra and maximum roughness Rt) of wire electrical discharge machined fine-pitch miniature spur gears made of brass. Effects of four wire electrical discharge machining process parameters (i.e. voltage, pulse-on time, pulse-off time and wire feed rate) on the surface roughness parameters of the miniature gears were studied by conducting 29 experiments with two replicates each and designed based on Box–Behnken approach of response surface methodology. Analysis of variance study found all four input parameters to be significant. Experimentally, the surface roughness has been found to increase with higher voltage and longer pulse-on time and decrease with longer pulse-off time and higher wire feed rate. Desirability analysis was used to optimize the wire electrical discharge machining parameters, so as to minimize the Ra and Rt simultaneously. Optimum values of Ra and Rt obtained from the confirmation experiments conducted at the optimized wire electrical discharge machining parameters are superior than the values reported in the literature. Artificial neural network model has been developed for prediction of the surface roughness of the wire electrical discharge machined miniature gears. Very close agreement was found among the surface roughness values predicted by response surface methodology and artificial neural network with the corresponding experimental values.

Precision Finishing of Bevel Gears by Electrochemical Honing

This article presents some studies on precision finishing of straight bevel gears using electro-chemical honing (ECH) process. Surface roughness and form errors in terms of pitch and runout error have been studied as process performance measures. An innovative experimental setup has been designed and developed for ECH of bevel gears using a novel concept of twin complementary cathode gears. It ensures finishing of the entire face width of the workpiece gear and the inter-electrode gap required for the ECM action to take place. In this concept, one of the cathode gears has an undercut conducting layer sandwiched between two insulating layers while, in the other cathode gear, an insulating layer is sandwiched between two undercut conducting layers. The results have shown noticeable improvement in the surface finish and form accuracy in an optimized finishing time of 2 minutes. The scanning electron microscope (SEM) images and bearing area curves have also shown improvement in the surface integrity and material contact ratio thus ensuring enhanced tribological performance and maximum service life of the gears. All these results have proven ECH as a viable and productive alternative gear finishing process.

Comparative Study of Wire-EDM and Hobbing for Manufacturing High-Quality Miniature Gears

With increasing emphasis on miniaturization, the demand for manufacturing the high-quality fine-pitched miniature gears is growing continuously. Inability of the conventional processes to manufacture high-quality miniature gears compels the need to explore a process which can economically manufacture precise and accurate gears required by the various miniature products used for different scientific, industrial, and domestic applications. This article reports on exploring and subsequently establishing wire electric discharge machining (WEDM) process as a superior, economical, and viable alternative for manufacturing the high-quality miniature gears through a comparative evaluation of process capabilities of WEDM and gear hobbing which is the most commonly used conventional process. The evaluation concentrated on those capabilities of these two processes which affect functional performance and service life of the miniature gears. This included microgeometry parameters (i.e., profile error and pitch error) and surface integrity aspects (i.e., surface topography, surface roughness, microhardness, and microstructure). The miniature gears manufactured by WEDM were found to be of superior quality (of DIN standard 5) and surface integrity than the hobbed gears (of DIN standard 10).

On Micro-Geometry of Miniature Gears Manufactured by Wire Electrical Discharge Machining

This article presents the investigations on micro-geometry of fine pitch miniature spur gears manufactured by wire electrical discharge machining (WEDM). Effects of voltage, pulse-on time, pulse-off time, wire feed rate and cutting speed on total profile and accumulated pitch errors were studied using one-factor-at-a-time approach. The miniature gears had a module of 0.7 mm, outside diameter 9.8 mm, face width 4.9 mm, and were made of brass. The best quality manufactured gear had DIN quality number of 6 and 8, respectively, for pitch and profile with average and maximum surface roughness values of 1 µm and 6.4 µm, respectively, establishing WEDM as a superior process for miniature gear manufacturing. It was observed that wire-lag and irregular shaped craters produced by high discharge energy parameters are responsible for micro-geometry errors of miniature gears manufactured by WEDM. Use of low voltage and pulse-on time, avoiding high pulse-off time, maximum values of wire feed rate and cutting speed are recommended to manufacture the high quality miniature gears by efficient and stable WEDM. This study found 5–15 V for voltage, 0.6–1.0 µs for pulse-on time, 90–170 µs for pulse-off time, 9–15 m/min for wire feed rate, and 100% cutting speed as the optimum settings for further investigations.

Modelling and Optimization

Modelling and optimization of WSEM parameters are discussed in this chapter. Regression analysis and artificial neural networks (ANN) were employed for WSEM process modelling. While RSM-based desirability analysis and back-propagation neural network (BPNN) integrated genetic algorithms (GA) approaches were used for single-objective and multi-objective optimization of WSEM parameters aimed to minimizing micro-geometry errors, surface roughness and enhancing the WSEM productivity for miniature gear manufacturing. Validation experiments were conducted to verify the results of optimization and correspondingly reported in this chapter.

Effects of electrolyte composition and temperature on precision finishing of spur gears by pulse electrochemical honing (PECH)

This paper presents the experimental findings to explore the effects of electrolyte in improving surface quality of gear teeth profile during precision finishing of spur gears by pulse electrochemical honing (PECH) process. Electrolyte composition and electrolyte temperature were used as input process parameter while percentage improvement on average and maximum surface roughness values (PIRa and PIRtm) was used as measure of process performances. The experimentation was carried out in an indigenously developed experimental setup for PECH. Optimum values of electrolyte composition and electrolyte temperature have been estimated using graphical analysis. Work-samples were analysed before and after the process using optical profilometer to visualise the improvement in surface finish of gear teeth profile. Key features of the developed PECH setup are also highlighted.