Mumbai University > Mechanical Engineering > Sem 5 > Production process 3

Marks: 5 M

Year: Dec 2014

Introduction:

• Non-traditional machining process is defined as a group of processes that remove excess material by various techniques involving mechanical, electrical, chemical and thermal energy used in non-traditional machining process.
• Extremely hard and brittle material is difficult to machine by traditional machining process such as turning, boring, drilling, shaping and milling.
• Non-traditional machining is also called advance manufacturing process.
• Several types of non-traditional machining processes have developed to better machining condition.
• When these machines are employed, they are many advantages over the traditional machining process.

Classification of non-traditional machining is based on following factors

• Mode and type of Energy: Mechanical, Electro-chemical, Chemical, Thermo-electric etc
• Energy source: Pneumatic or Hydraulic, High current or voltage, mechanical pressure
• Medium of energy transfer: High velocity particles, physical contact, electrolyte, radiation etc
• Metal removal mechanism: Vaporization, Erosion, spark erosion etc.

Electro discharge machining (EDM):

Working of Electro discharge machining (EDM) :

• The diagram of electro discharge machining shown in figure.

Electro Discharge Machine construction and working

• This is also called spark erosion, electro-erosion machining.
• EDM is thermal erosion process whereby material is melted and vaporized from an electrically conductive work piece immerse in a liquid dielectric with a series of spark discharge between the tool electrode and the work piece created by a power supply.
• The electrode and the work piece are separated by a dielectric medium.
• The dielectric medium is like as kerosene, paraffin or light oil.
• The strong electrostatic field between the electrode and work piece produce emission of electrons from the cathode.
• In this gap between tool and work piece get ionized. The liquid is force to sparking zone.
• Due to high temperature, the metal at the sparking zone melts instantaneously.
• The material of the tool is usually a material which conduct electricity and which can be easily shaped.

Advantages of Electro discharge machining (EDM):

• Smaller holes can be easy machined.
• No contact between tool and work piece then tool life is increase.
• Any complex shape can be machined.

Disadvantages of Electro discharge machining (EDM):

• Tool life doesn’t long last
• Power consumption is high.
• Cycle time is more.