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Electro Discharge

Machine

Lab-5

METEREOLOGY & MACHINING LAB

SUMIT JADHAV

ME10B017 | Lab-5

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OBJECTIVE:

To get acquainted with one of the non-Conventional machining methods, ELECTRO DISCHARGE

MACHINING by machining an ASTM standard fatigue and tensile specimen

APPARATUS REQUIRED:

1. Electronicas EDM machine.2. High conducting brass wire.3. Computer software for solid modelling of desired part.4. Fanuc's software to generate the CNC program based upon the input 2D geometry (.dxf File

Format)

THEORY:

Electric discharge machining (EDM), sometimes also referred to as spark machining/ spark eroding, is a

manufacturing process whereby a desired shape is obtained using electrical discharges (sparks).Materialis removed from the work piece by a series of rapidly recurring current discharges between two

electrodes, separated by a dielectric liquid and subject to an electric voltage.

One of the electrodes is called the tool-electrode, or simply the tool or electrode, while the other is

called the work piece-electrode, or work piece.

The wire used as electrode is made up of copper-zinc alloy. It has good conductance process which is a

must for this process. The wire is negative terminal and the work-piece is the positive terminal. Upon

passing the current, fast moving electrons are emitted from the wire which moves at a high velocity due

to the presence of a strong electric field created by the presence of a dielectric material.

Upon reaching the work-piece, the fast moving electrons collide with the work-piece thereby convertingthe total kinetic energy in the form of thermal energy which helps in cutting/abrading the work-piece.

The machine used in the workshop is a 4-axes machine. It uses de-ionized water as the dielectric

material and brass wires as the negative electrode. The u and v axes are generally used to create

tapered cuts.

The wire-cut process uses water as its dielectric fluid, controlling its resistivity and other electrical

properties with filters and de-ionizer units. The water flushes the cut debris away from the cutting zone.

Flushing is an important factor in determining the maximum feed rate for a given material thickness.

The wire-cut process uses water as its dielectric fluid, controlling its resistivity and other electrical

properties with filters and de-ionizer units. The water flushes the cut debris away from the cutting zone.

Flushing is an important factor in determining the maximum feed rate for a given material thickness.

Current passing through the wire is generally in the form of discrete pulses.

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Why not use copper wire even if it is more conductive:

1. Low tensile strength of Cu (if high tension is applied it breaks).2. Poor flush ability (A good portion of the heat from the EDM spark was transferred to the wire

and carried away from the work-zone instead of using that heat to melt and vaporize the work-

piece).3. By optimization they chose Brass as standard one.

PROCEDURE:

1. Create the 3d models of desired components to be manufactured.2. Prepare a .dxf file which contains the top view of the modelled component.3. Import the .dxf file into the automatic CNC program generator software and follow the

stipulated procedure to obtain the CNC code for thedesired geometry.

4. Using a USB flash drive, transfer the program to the EDM machine controller computer.5. Load the generated program into the Controller's RAM and start the cutting operation.6. The CNC machine guides the electrode (wire) into the desired places where the cut is to be

formed.

Created 2D models:

FATIGUE FLAT MODEL

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TENSILE FLAT MODEL

CNC CODE GENRATED BY THE COMPUTER:

5.3.2013,11:00:10

G71

G9

G27

G40

G47

G50

G90

G75

; Wire Compensation Definitions

D0=0

D1=0.175

;#1.0 Cavity=1 RoughCut

G0 X-194.0481493 Y-100.606529 U0 V0

M21

G41 D0 ;D0=0

G1 X-194.0481493 Y-98.606529

G41 D1 ;D1=0.175

G1 X-170.708872 Y-98.606529

G1 X-170.708872 Y-98.606529

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G1 X-270.708872 Y-98.606529

G1 X-270.708872 Y-98.606529

G1 X-194.081493 Y-98.606529

M0

G41 D0; D0=0

G1 X-194.0481493 Y-100.606529

G40

M0

OBSERVATIONS & CONCLUSIONS:

1. EDM process has been effectively put into use to generate the required model.2. Heat affected zone is limited to 2-4 mm of spark crater. The accuracy of the process is very high

compared to that of conventional machining techniques.3. The residual stresses developed in the machined component are less because of the reduced

forces of cutting.

4. The time consumed in the process is pretty high and hence there is a trade-off betweenmachining accuracy and time to machine.

5. Intricate parts which require a lot of detailing can be machined using this technique.6. Hence, although more accurate, there is less acceptance in mainstream industry due to low

productivity but this technique becomes ubiquitous where high accuracy is desired and

complexity of the component is high.

LEARNING: 1. How to operate the EDM machine and the set-up required before the commencement of the

actual machining operation.

2. The need for non-conventional machining techniques.3. The process of EDM, it's pros and cons and applicability.4. Using computer software to generate 3d solid models and to obtain the CNC code directly from

the solid model using real time simulation software.