PARAMETRIC OPTIMIZATION OF Al-SiC 12 % METAL MATRIX COMPOSITE MACHINING BY ELECTRICAL DISCHARGE MACHINE
In the present study, pure aluminium alloy is mixed with 12% SiC on weight basis to fabricate the metal matrix composite (MMC) material. The objective of this paper is to investigate the effect of process parameters such as pulse on time(Ton), peak current (Ip) and flushing pressure (Fp) on metal removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) during electrical discharge machining (EDM) of Al-SiC12% MMC .The experiment is followed by Central composite design (CCD) method under different combination of process parameters .In this paper Response surface methodology (RSM) is used to develop the mathematical model and to correlate the process parameters with the response. Also Analysis of Variance (ANOVA) technique is used to check the significance of the model and confirmation test is conducted to compare the experimental data with the predicted data to identify the effectiveness of the proposed method. From the main effective plot it is found that peak current is the most significant parameter among the other. Further the morphology study of the composite is carried out by the Field emission Scanning electron microscope (FESEM) of the surface after machining to make a relation with the model.
Experimental investigations on machining characteristics of Al 6061 hybrid metal matrix composites processed by electrical discharge machining
Metal matrix composites, in particular, Aluminium Matrix Composites are gaining increasing attention for applications in aerospace, defence and automobile industries. The use of nonconventional machining techniques in shaping aluminum metal matrix composites has generated considerable interest as the manufacturing of complicated contours such as dies. Electrical discharge machining (EDM) appears to be a promising technique for machining metal matrix composites. The objective of this work is to investigate the effect of parameters like Current(I), Pulse on time(T), Voltage(V) and Flushing pressure(P) on metal removal rate (MRR), tool wear rate(TWR) as well as surface roughness(SR) on the machining of hybrid Al6061 metal matrix composites reinforced with 10% SiC and 4%graphite particles. Composite was fabricated using stir casting process. A central composite rotatable design was selected for conducting experiments. Mathematical models were developed using the MINITAB R14 software. The method of least squares technique was used to calculate the regression coefficients and Analysis of Variance (ANOVA) technique was used to check the significance of the models developed. Scanning Electron Microscope (SEM) analysis was done to study the surface characteristics of the machined specimens and correlated with the models developed.
Electric discharge milling of silicon carbide ceramic with high electrical resistivity
Abstract Silicon carbide (SiC) ceramics have been widely used in modern industry. However, the manufacture of SiC ceramic blanks is not an efficient process. The shaping of SiC ceramic blanks with conventional machining methods (such as grinding) is a long, labour-intensive and costly process. Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical techniques for the production of tools and parts from conducting ceramic blanks that their electrical resistivity is below of 100 Ω cm. However, these electrodischarge-machining methods of machining a large surface area on ceramics that their electrical resistivity is higher than 100 Ω cm shows low efficiency. This paper employs a steel toothed wheel as the tool electrode to machine SiC ceramics with specific resistivity of 500 Ω cm using electrical discharge milling. The process employs the pulse generator used in EDM, and uses a water-based emulsion as the machining fluid. It is able to effectively machine a large surface area on SiC ceramics with electrical resistivity of 500 Ω cm. The effects of tool polarity, peak voltage, pulse on-time, pulse off-time, and peak current on process performance have been investigated.