Electro discharge machining

ELECTRO DISCHARGE MACHINING

SUBMITTED BY:ANSHUL AHUJAMM-662-2K15

In1770s, discovered by Joseph Priestly. Developed in the mid 1970s In the mid 1980s, the EDM techniques

were transferred to a machine tool Today, it is a viable technique that

helped shape In the metal working industry

INTRODUCTION

ELECTRO DISCHARGE MACHINING Electrical Discharge Machining

(EDM) is a controlled metal-removal process that is used to remove metal by means of electric spark erosion. In this process an electric spark is used as the cutting tool to cut (erode) the work piece to produce the finished part to the desired shape.

CHARACTERSTICS OF EDM The process can be used to machine

any work material if it is electrically conductive

Material removal depends on mainly thermal properties of the work material rather than its strength, hardness etc.

However rapid heating and cooling and local high temperature leads to surface hardening which may be desirable in some applications

Though there is a possibility of taper cut and overcut in EDM, they can be controlled and compensated.

KEY POINT OF EDM potential difference is applied between

the tool and work piece Both the tool and the work material are

to be conductors of electricity A gap is maintained between the tool

and the work piece As the electric field is established

between the tool and the job, the free electrons on the tool are subjected to electrostatic forces

MECHANISM OF EDM:-

EQUIPMENTS

Dielectric reservoir, pump and circulation system

Power generator and control unit Working tank with work holding device X-y table accommodating the working

table The tool holder The servo system to feed the tool

CONSTRUCTIONAL SET UP

DIELECTRIC

Main Functions Of Dielectric Fluid Methods Of Circulating Dielectrics –

Flushing Characteristics Of Dielectrics Types Of Dielectrics

ELECTRODE Shape Characteristics of electrode Materials of electrodes

1) copper2)Graphite3)copper alloy.

MODELLING OF MATERIAL REMOVAL

PRODUCT QUALITY ISSUES

surface finish over cut Taper cut

PARAMETERS AFFECTING EDM

POWER SUPPLY BASIC PROPERTY OF POWER SUPPLY TYPES OF POWER SUPPLY

1)Resistance-capacitance type (RC type) Relaxation generator 2)Rotary impulse type generator 3)Electronic pulse generator 4)Hybrid EDM generator

TYPES OF EDM RAM TYPE EDM WIRE CUT EDM DRILLING TYPE EDM

ADVANTAGE 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 perceivable distortion.

A good surface finish can be obtained; a very good surface may be obtained by redundant finishing paths.

Very fine holes can be attained. Tapered holes may be produced.

DISADVANTAGE OF EDM The slow rate of material removal. Potential fire hazard associated with use

of combustible oil based dielectrics. The additional time and cost used for

creating electrodes for ram/sinker EDM. Reproducing sharp corners on the work

piece is difficult due to electrode wear. Specific power consumption is very high. Power consumption is high. "Overcut" is

formed. Excessive tool wear occurs

Metal-removal rates are low Material to be machined must be electrically

conductive Cavities produced are slightly tapered but

can be controlled for most applications to as little as .0001 in. in every .250 in.

Rapid electrode wear can be come costly in some types of EDM equipment

Electrodes smaller than .003 in. in diameter are impractical

Work surface is damaged to depth of .0002 in. but is easily removed

LIMITATIONS OF EDM

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