LECTURE PRESENTATION

Reading Assignment

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

Additional Reading

• Electrical Discharge Machining.  2001,  Elman C. Jameson and the Society of Manufacturing Engineers

Outline

Classification

History of EDM

Types

Ram (Sinker)

Wire

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

Functions

• 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

Limitations

• 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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