OCTOBER 19-20, 2012 - YMCA University of Science & Technology

7.4 Dry EDM
Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Dry machining was introduced by M. Kunieda et al. where by supplying gas into gap between
the electrode and work piece. It resulted to repeated rate of discharge happened thus enhance the
MRR. MRR is six times greater and TWR only one-third than machining in oil. Some other
advantages are low residual stress and no need of working basin, fluid tank and fluid circulation
system. Development on dry EDM research can be obtained from Norliana Mohd Abbas et al.
where until 2005 hybrid activity viz. combination dry EDM with ultrasonic vibration has taken
place.
7.5 Small Hole EDM
Small Hole EDM drilling uses the same spark erosion principle as Sinker or Ram EDM. Small
Hole EDM drilling is ideal for putting ejector holes in hardened punches, coolant holes in
cutting tools, vent holes in molds, and start holes for Wire EDM. Small Hole EDM machines use
the EDM process to blast through hardened materials that cannot be conventionally machined.
Small Hole EDM machines ideally complement our Wire EDM machines with the ability to
quickly blast Wire EDM start holes in our work pieces for minimal material preparation times,
which gives the fastest turnarounds possible to our customers. Small Hole EDM Diameters
range from .155mm to 3.0mm. Part Heights up to 12” can be Small Hole EDM Drilled.
7.6 Advantages of EDM
• Complex shapes that would otherwise be difficult to produce with conventional cutting tools
• Extremely hard material to very close tolerances
• Very small work pieces where conventional cutting tools may damage the part from excess cutting tool
pressure.
• There is no direct contact between tool and work piece. Therefore delicate sections and weak materials can
be machined without any distortion.
• A good surface finish can be obtained.
• Very fine holes can be easily drilled.
7.7 Disadvantages of EDM
• The slow rate of material removal.
• The additional time and cost used for creating electrodes for ram/sinker EDM.
• Reproducing sharp corners on the workpiece is difficult due to electrode wear.
• Specific power consumption is very high.
• Power consumption is high.
• "Overcut" is formed.
• Excessive tool wear occurs during machining.
• Electrically non-conductive materials can be machined only with specific set-up of the process
8. Hybrid EDM Processes
Hybrid machining process in EDM make use of the combined advantages and to reduce some negative effects the
combined processes produce better performance as compared to individual process machining. In EDM process the
electrical energy is converted to thermal energy, the combined effect of powder suspension and ultrasonic motion of
tool or work piece as been reported in this section.
8.1 Powder mixed EDM (PMEDM)
EDM process in pure kerosene shows instability resulting to the arcing effect. In order to improve the machining
efficiency, the addition of abrasives and metallic powders is done to dielectric fluid. Erden et al. research out the
effect of suspended powder particles (Al, Cu, Fe, and carbon) on the mach inability of mild steel. It was observed
664