INVESTIGATIONS ON PERFORMANCE ENHANCEMENT OF POWDER-MIXED NEAR-DRY ELECTRICAL DISCHARGE MACHINING

Abstract

In this thesis a newly developed hybrid form of Electric Discharge Machining have been described which is Powder-Mixed Near- Dry Electric Discharge machining and it would help the researchers to understand the technique how to get better surface characteristics by utilizing minimum amount of dielectric fluids. The contents of the thesis are as follows: Chapter 1 This chapter includes the background of electric discharge machining and its evolution in modern world. Afterwards, its principle was discussed along with material removal mechanism. Details regarding EDM machine and its components were also discussed in elaborated manner. Further advantages, limitation and application of EDM were discussed. Lastly types of EDM and its hybrid forms were explained. Chapter 2 This chapter deals with review of the literature study conducted by researchers in field of EDM and its hybrid forms. Several studies have been conducted related to surface finish, material removal rate, tool wear rate, micro-hardness and residual stress. .Chapter 3 This chapter includes preview of present investigation. The objectives of the present study and scope of the problem were evaluated by reviewing the literature review critically. Additionally, problem formulation was described for the lacking information pertaining to EDM process, thereafter the problems were described which needed to be solved through this present work. Chapter 4 The Design of experiment was introduced in this chapter for experimentation planning. Further Taguchi methodology along with analysis of variance was studied for process optimization of the developed process of Powder Mixed Near Dry EDM. This chapter also gives information related to steps involved in Taguchi methodology and application of analysis of variation (ANOVA) in various research fields. Lastly scheme of experiments has been discussed along with instruments used for measurement of different response characteristics. Chapter 5 This chapter includes information related to Electric Discharge Machine and design of powder mixed near dry electric discharge machining (PMND-EDM) setup and it’s another form of gaseous assisted powder mixed near dry EDM (GAPMND-EDM) setup. The specification of the used parts was defined along with the operational condition of the indigenously developed setup. Afterwards, details of tool electrode fabrication and its design were also discussed. iv Chapter 6 This chapter describes parameters selected for experimentation in powder mixed near dry EDM and gaseous assisted EDM. Afterwards selection of response characteristics was elaborated. Variable parameters such as tool type, metallic powder concentration, dielectric mist pressure, mist flow rate, types of gases, and types of metallic powders were discussed along with their range in order to optimize the process parameters for enhancing the machining performance in terms of increased material removal rate, improved surface finish, improved micro-hardness, reduction of residual stress and tool wear rate. Lastly, the instruments used for measuring response characteristics were discussed. Chapter 7 This chapter includes thermal-physical based modeling for material removal in Powder Mixed Near-Dry Electric Discharge Machining. This research includes three-dimensional axisymmetric model for PMND-EDM. Thermal properties of material, heat source shape (Gaussian heat distribution), heat distribution percentage among workpiece, tool and dielectric fluid, pulse on, pulse off and material ejection efficiency were considered as significant elements for predicting the MRR in PMND-EDM. Chapter 8 This chapter includes result and discussion related to present investigation. This section includes validation of model through experimental and analytical means. Further discussion was related to optimization of process parameters and their effect on output performance characteristics. The best combination of the parameters was found for improving the machining efficiency. Later confirmation experiments were conducted to verify the results. Lastly analysis of machining performance was done based on gaseous assisted EDM with powder additives. Chapter 9 This chapter contains salient conclusions. Important conclusions of the investigation regarding MRR, Ra, TWR, MH and RS are stated in this end part of the thesis. This chapter also introduces scope for further research in this field. Significant findings have been drawn from performed experimentation.