Electric Discharge Machining Process

Which one the following statements is true for Electrical Discharge machining (EDM)?

i. The material removal takes place due to the melting and evaporation of the workpiece material.

ii. Any electrical conductor can be machined by this method.

iii. Some light oil like transformer oil or kerosene oil is used as dielectric.

• Only i

• i & ii

• i, ii & iii

• ii & iii

Which one of the following statements is not true in case of EDM?

• Erosion takes place both on work piece and tool.

• Gap between tool and work piece is controlled by servo mechanism.

• The size of impression on the work piece surface is exactly same as that of electrode (tool).

• The electrode (tool) is made of graphite or copper.

During EDM, the temperature developed at the point of spark is of the order of

• 2,000°C

• 6,000°C

• 10,000°C

• 14,000°C

In EDM the metal removal is carried out by

• fracture of work material due to impact of grains

• electrolysis

• melting and vaporization

• none of the above

Preferable tool properties in EDM are

• High electrical conductivity, low thermal conductivity

• low electrical conductivity, High thermal conductivity

• High electrical conductivity, High thermal conductivity

• low electrical conductivity, low thermal conductivity

In EDM the material of the tool is

• Satellite

• Diamond

• Carbide

• High speed steel

• Copper

Undesirable characteristic of graphite electrode is

• Higher TWR

• Poor surface finish

• Brittleness

• All of the above

EDM is not suitable for machining of

• Very hard metals

• Glass

• Fragile metallic components

• None of the above

Which of the following is used as dielectric medium in EDM

• tap water

• kerosene

• NaCL solution

• KOH solution

An ____________ is a material that does not allow electrons to easily flow through it.

• conductor

• insulator

• blanket