Electrical Discharge Machining


EDM Video Lectures by Carl Sommer

Reading Assignment

  • 19.1 Introduction to Electronic, Electrochemical, Chemical, and Thermal Machining Processes
  • 19.4 Electrical Discharge Machining

Recommended Reading



History of EDM


Ram (Sinker)


Process Fundamentals

Factors Affecting Surface Finish

  • Gap voltage at discharge
  • Discharge Current
  • Current “on time” – the time current flows
  • Frequency
  • Generally, the feed rate is inversely proportional to the finish quality

Dielectric Fluid


  • Provide a path for the discharge of electric current.
  • Cool the workpiece.
  • Remove metal particles from the gap

Benefits of EDM Process

  • EDM is a non-contact process that generates no cutting forces, permitting the production of small and fragile pieces
  • Burr-free edges are produced
  • Intricate details and superior finishes are possible
  • EDM machines with built-in process knowledge allow the production of intricate parts with minimum operator intervention
  • EDM can easily machine hard materials like hardened tool steel


  • low metal removal rates compared to chip machining
  • lead time is needed to produce specific, consumable electrode shapes

Ram EDM Subsystems

  • a DC power supply to provide the electrical discharges, with controls for voltage, current, duration, duty cycle, frequency, and polarity
  • a dielectric system to introduce fluid into the voltage area/discharge zone and flush away work and electrode debris, this fluid is usually a hydrocarbon or silicone-based oil
  • a consumable electrode, usually of copper or graphite
  • a servo system to control in-feed of the electrode and provide gap maintenance

Additional Resources

EDM Today Magazine – Technical Articles


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