18-01-2013, 03:21 PM
ELECTRIC DISCHARHE MACHINING OF TOOL STEEL USING DIFFERENT ELECTRODE MATERIALS
ELECTRIC DISCHARHE.pptx (Size: 225.69 KB / Downloads: 41)
INTRODUCTION
WHAT IS ELECTRIC DISCHARGE MACHINING
non-traditional machining process.
Capable of machining geometrically complex or hard material components such as heat treated tool steels, composites, super alloys, ceramics, etc.
widely used in die and mould making industries, aerospace, aeronautics, and nuclear industries.
PRINCIPLE OF EDM
Thermo-electrical material removal process.
Electrical energy is used to generate electrical spark.
material removal mainly occurs due to thermal energy of the spark.
ELECTRIC DISCHARGE MACHINING PROCESS
In EDM, The tool is connected to the negative terminal of the generator and the work piece is connected to positive terminal.
The tool and the work material are immersed in a dielectric medium.
A potential difference is applied between the tool and work piece.
Depending upon the applied potential difference and the gap between the tool and workpiece, an electric field would be established.
EXPERIMENT PROCEDURE
The initial mass of electrode was measured with single pan electrical balance.
After EDMing, final weight of electrode was measured.
Optical microscope is used to measure the diameter of eroded hole.
A surface roughness tester is used to measure surface roughness.
Experiment is repeated for different electrode materials.
MATERIAL REMOVAL RATE AGAINST DISCHARGE CURRENT
The spark discharge energy is increased to facilitate the action of melting and vaporization.
MRR is also dependent upon the electrode material and work material.
The MRR is also controlled by the frequency of the sparks.
Low discharge currents and higher frequencies correspond to low stock removal
SURFACE ROUGHNESS AGAINST DISCHARGE CURRENT
copper–tungsten gives low values of surface roughness at high discharge current
Copper and aluminium electrode results in poor machined surface at high currents.
Brass also gives good performance with small surface roughness.
CONCLUSION
Copper and Aluminium electrodes offer higher MRR.
Copper and copper–tungsten electrodes offer comparatively low electrode wear for the tested work material.
Copper–tungsten electrode offers comparatively low values of surface roughness at high discharge currents.
At low discharge current, Copper gives better surface finish.
Copper is comparatively a better electrode material for En-31 work material.