B. Bhattacharyya

An analysis and optimisation of the geometrical inaccuracy due to wire lag phenomenon in WEDM

Abstract An extensive study of the wire lag phenomenon in Wire-cut Electrical Discharge Machining (WEDM) has been carried out and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established in this paper. In an extremely complicated machining process like Wire-cut EDM, which is governed by as many as ten control factors, it is very difficult to select the best parametric combination for a particular situation arising out of customer requirements. In the present research study, all the machine control parameters are considered simultaneously for the machining operation which comprised a rough cut followed by a trim cut. The objective of the study has been to carry out an experimental investigation based on the Taguchi method involving thirteen control factors with three levels for an orthogonal array L27 (313). The main influencing factors are determined for given machining criteria, such as: average cutting speed, surface finish characteristic and geometrical inaccuracy caused due to wire lag. Also, the optimum parametric settings for different machining situations have been found out and reported in the paper.

Experimental investigation on the influence of electrochemical machining parameters on machining rate and accuracy in micromachining domain

Abstract Non-conventional machining is increasing in importance due to some of the specific advantages which can be exploited during micromachining operation. Electrochemical micromachining (EMM) appears to be a promising technique, since in many areas of application, it offers several special advantages that include higher machining rate, better precision and control, and a wider range of materials that can be machined. A better understanding of high rate anodic dissolution is urgently required for EMM to become a widely employed manufacturing process in the micro-manufacturing domain. An attempt has been made to develop an EMM experimental set-up for carrying out in depth research for achieving a satisfactory control of the EMM process parameters to meet the micromachining requirements. Keeping in view these requirements, sets of experiments have been carried out to investigate the influence of some of the predominant electrochemical process parameters such as machining voltage, electrolyte concentration, pulse on time and frequency of pulsed power supply on the material removal rate (MRR) and accuracy to fulfil the effective utilization of electrochemical machining system for micromachining. A machining voltage range of 6 to 10 V gives an appreciable amount of MRR at moderate accuracy. According to the present investigation, the most effective zone of pulse on time and electrolyte concentration can be considered as 10–15 ms and 15–20 g/l, respectively, which gives an appreciable amount of MRR as well as lesser overcut. From the SEM micrographs of the machined jobs, it may be observed that a lower value of electrolyte concentration with higher machining voltage and moderate value of pulse on time will produce a more accurate shape with less overcut at moderate MRR. Micro-sparks occurring during micromachining operation causes uncontrolled material removal which results in improper shape and low accuracy. The present experimental investigation and analysis fulfils various requirements of micromachining and the effective utilization of ECM in the micromachining domain will be further strengthened.

Investigation for controlled ellectrochemical machining through response surface methodology-based approach

Abstract This paper highlights features of the development of a comprehensive mathematical model for correlating the interactive and higher-order influences of various machining parameters on the dominant machining criteria, i.e. the metal removal rate and the overcut phenomena, through response surface methodology (RSM), utilising relevant experimental data as obtained through experimentation. This paper also highlights the various test results that also confirm the validity and correctiveness of the developed mathematical models for analyzing the effects of various process parameters on the machining rate and overcut phenomena. Optimal combination of these parameters can be used in order to achieve maximisation of the metal removal rate and the minimum overcut effects for optimal accuracy of shape features.

Electrochemical micro-machining: new possibilities for micro-manufacturing

Abstract Electrochemical micro-machining (EMM) appears to be very promising as a future micro-machining technique since in many areas of applications it offers several advantages. The paper highlights the design and development of an EMM system set-up which includes various components such as mechanical machining components, electrical systems and an electrolyte flow system, etc. A microprocessor controlled end-gap controlling system has also been developed for this purpose. The developed EMM set-up will open up many challenging possibilities for effective utilizations of the electrochemical material removal mechanism in micro-machining.

Experimental investigation into electrochemical micromachining (EMM) process

Abstract Due to several advantages and wider range of applications, electrochemical micromachining (EMM) is considered to be one of the most effective advanced future micromachining techniques. A suitable EMM setup mainly consists of various components and sub-systems, e.g. mechanical machining unit, micro-tooling system, electrical power and controlling system and controlled electrolyte flow system etc. have been developed successfully to control electrochemical machining (ECM) parameters to meet the micromachining requirements. Investigation indicates most effective zone of predominant process parameters such as machining voltage and electrolyte concentration, which give the appreciable amount of material removal rate (MRR) with less overcut. The experimental results and analysis on EMM will open up more application possibilities for EMM.

Modelling and analysis of the wire-tool vibration in wire-cut EDM

Abstract Although wire-cut electrical discharge machining (WEDM) has revolutionised the present day metal cutting, die making and press tool manufacturing industries, further improvements are still required to meet the increasing demand of product precision and accuracy in those sectors of manufacturing. The machining performance in this regard is greatly influenced by the wire-tool vibration occurring during machining. This paper briefs an account of the vibrational behaviour of the wire and presents an analytical approach for the solution of the wire-tool vibration equation considering multiple spark discharges to investigate into the characteristic effects of wire vibration in WEDM. It includes the output of the model depicting the influence of the pulse discharge frequencies under various wire tensions on the maximum amplitude of wire vibration. Also, the trend of variation of the maximum amplitude of the wire vibration with the ratio of ‘the height of a job’ to ‘the span of the wire between the guides’ has been studied and reported in the paper.

Development of an expert system for turning and rotating tool selection in a dynamic environment

Abstract In metal cutting, the selection of a proper cutting tool plays a significant role in achieving consistent quality and in controlling the overall cost of manufacturing. However, searching for a proper tool/insert — job combination calls for a huge amount of data and an extensive knowledge base. In the present paper, the manual effort of searching is substituted for by E xtool , an expert system, which automatically selects the turning tool/insert or milling insert, the material and the geometry, based on the requirements of users. Trade-off among the different cutting parameters of the operation is also performed by the developed system as and when necessary. The application of this developed expert system is highlighted by executing some practical problems. This research effort can be of great use in manufacturing industries for optimum use of their resources.

Parametric control for optimal quality of the workpiece surface in ECM

Abstract The authors have successfully designed and developed an Electrochemical Machining set-up with a microprocessor-controlled stepper motor drive control unit for providing variable and automatic tool feed rates and also with an electronic circuit for auto-sensing of changes of the ECM gap condition during the course of machining, so as to actuate the auto-feedback control of the tool feed-rate and thus secure constant current Electrochemical Machining. The present paper also highlights various research results with the auto-feed ECM system for analysing the effect of some of the process variables, e.g. the electrolyte flow rate, the electrolyte concentration, the current density and the applied voltage, on the various surface-roughness parameters and bearing properties of the machined surface, as measured with the help of a computerised Talysurf unit. The test results indicate clearly the optimal parametric combinations that are needed for enhanced metal removal and better surface finish and other surface topographical characteristics, with the present design of auto-tool-feed control. It is evident from the test results that the present study on ECM will be quite useful and a step forward for proceeding with further applied research for achieving effective utilisation of ECM in practice, with better surface-quality characteristics so as to meet the needs of modern manufacturing industry.