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Electrochemical

Electrochemical

Machining

Machining

(ECM)

(ECM)

Dr. Lotfi K. Gaafar

Dr. Lotfi K. Gaafar

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AUC - MENG

Electrochemical

Electrochemical

Machining

Machining

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Electrochemical

Electrochemical

Machining

Machining

Uses an electrolyte and electrical current to

Uses an electrolyte and electrical current to

ionize and remove metal atoms

ionize and remove metal atoms

Can machine complex cavities in high-

Can machine complex cavities in high-

strength materials

strength materials

Leaves a burr-free surface

Leaves a burr-free surface

Not affected by the strength, hardness or

Not affected by the strength, hardness or

toughness of the material

toughness of the material

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Electrochemical

Electrochemical

Machining

Machining

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Operating Principle

Operating Principle



As the tool approaches

As the tool approaches

the work piece it

the work piece it

erodes the negative

erodes the negative

shape of it. Thus

shape of it. Thus

complex shapes are

complex shapes are

made from soft copper

made from soft copper

metal and used to

metal and used to

produce negative

produce negative

duplicates of it. This

duplicates of it. This

process is called

process is called

electrochemical

electrochemical

sinking

sinking

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Operating Principle

Operating Principle



The tool may also be connected to a CNC machine to

The tool may also be connected to a CNC machine to

produce even more complex shapes with a single tool.

produce even more complex shapes with a single tool.

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Operating Principle

Operating Principle



Several tools may be joined to

Several tools may be joined to

provide a fast broaching technique

provide a fast broaching technique

on hardened material.

on hardened material.



Conventional machines may be

Conventional machines may be

easily changed to an ECM and is a

easily changed to an ECM and is a

common practice.

common practice.

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Main Subsystems

Main Subsystems



The power supply.

The power supply.



The electrolyte circulation system.

The electrolyte circulation system.



The control system.

The control system.



The machine.

The machine.

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ECM Components

ECM Components

(Power)

(Power)



The power needed to operate the ECM

The power needed to operate the ECM

is obviously electrical. There are many

is obviously electrical. There are many

specifications to this power.

specifications to this power.



The current density must be high.

The current density must be high.



The gap between the tool and the work

The gap between the tool and the work

piece must be low for higher accuracy,

piece must be low for higher accuracy,

thus the voltage must be low to avoid a

thus the voltage must be low to avoid a

short circuit.

short circuit.



The control system uses some of this

The control system uses some of this

electrical power.

electrical power.

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ECM Components

ECM Components

(electrolyte circulation

(electrolyte circulation

system)

system)



The electrolyte must be injected in the gap

The electrolyte must be injected in the gap

at high speed (between 1500 to 3000

at high speed (between 1500 to 3000

m/min).

m/min).



The inlet pressure must be between 0.15-3

The inlet pressure must be between 0.15-3

MPa.

MPa.



The electrolyte system must include a fairly

The electrolyte system must include a fairly

strong pump.

strong pump.



System also includes a filter, sludge removal

System also includes a filter, sludge removal

system, and treatment units.

system, and treatment units.



The electrolyte is stored in a tank.

The electrolyte is stored in a tank.

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ECM Components

ECM Components

(control system)

(control system)



Control parameters include:

Control parameters include:



Voltage

Voltage



Inlet and outlet pressure of electrolyte

Inlet and outlet pressure of electrolyte



Temperature of electrolyte.

Temperature of electrolyte.



The current is dependant on the

The current is dependant on the

above parameters and the feed rate.

above parameters and the feed rate.

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ECM Components

ECM Components

(Machine)

(Machine)



The machine is a major subsystem of

The machine is a major subsystem of

the ECM.

the ECM.



It includes the table, the frame, work

It includes the table, the frame, work

enclosure (prevents the electrolyte

enclosure (prevents the electrolyte

from spilling), the work head (where

from spilling), the work head (where

the tool is mounted)

the tool is mounted)



The tools (electrodes) are also part

The tools (electrodes) are also part

of the machine system

of the machine system

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Advantages

Advantages



There is no cutting forces therefore

There is no cutting forces therefore

clamping is not required except for

clamping is not required except for

controlled motion of the work piece.

controlled motion of the work piece.



There is no heat affected zone.

There is no heat affected zone.



Very accurate.

Very accurate.



Relatively fast

Relatively fast



Can machine harder metals than the

Can machine harder metals than the

tool.

tool.

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Advantages over EDM

Advantages over EDM



Faster than EDM

Faster than EDM



No tool wear at all.

No tool wear at all.



No heat affected zone.

No heat affected zone.



Better finish and accuracy.

Better finish and accuracy.

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Disadvantages

Disadvantages



More expensive than conventional

More expensive than conventional

machining.

machining.



Need more area for installation.

Need more area for installation.



Electrolytes may destroy the equipment.

Electrolytes may destroy the equipment.



Not environmentally friendly (sludge and

Not environmentally friendly (sludge and

other waste)

other waste)



High energy consumption.

High energy consumption.



Material has to be electrically

Material has to be electrically

conductive.

conductive.

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Applications

Applications



The most common application of ECM is high

The most common application of ECM is high

accuracy duplication. Because there is no tool

accuracy duplication. Because there is no tool

wear, it can be used repeatedly with a high

wear, it can be used repeatedly with a high

degree of accuracy.

degree of accuracy.



It is also used to make cavities and holes in

It is also used to make cavities and holes in

various products.

various products.



Sinking operations (RAM ECM) are also used

Sinking operations (RAM ECM) are also used

as an alternative to RAM EDM.

as an alternative to RAM EDM.



It is commonly used on thin walled, easily

It is commonly used on thin walled, easily

deformable and brittle material because they

deformable and brittle material because they

would probably develop cracks with

would probably develop cracks with

conventional machining.

conventional machining.

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Economics

Economics



The process is economical when a large

The process is economical when a large

number of complex identical products

number of complex identical products

need to be made (at least 50 units)

need to be made (at least 50 units)



Several tools could be connected to a

Several tools could be connected to a

cassette to make many cavities

cassette to make many cavities

simultaneously. (i.e. cylinder cavities in

simultaneously. (i.e. cylinder cavities in

engines)

engines)



Large cavities are more economical on

Large cavities are more economical on

ECM and can be processed in 1/10 the

ECM and can be processed in 1/10 the

time of EDM.

time of EDM.

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Products

Products



The two most common products of ECM are

The two most common products of ECM are

turbine/compressor blades and rifle barrels. Each of

turbine/compressor blades and rifle barrels. Each of

those parts require machining of extremely hard

those parts require machining of extremely hard

metals with certain mechanical specifications that

metals with certain mechanical specifications that

would be really difficult to perform on conventional

would be really difficult to perform on conventional

machines.

machines.



Some of these mechanical characteristics achieved

Some of these mechanical characteristics achieved

by ECM are:

by ECM are:



Stress free grooves.

Stress free grooves.



Any groove geometry.

Any groove geometry.



Any conductive metal can be machined.

Any conductive metal can be machined.



Repeatable accuracy of 0.0005”.

Repeatable accuracy of 0.0005”.



High surface finish.

High surface finish.



Fast cycle time.

Fast cycle time.

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Safety Considerations

Safety Considerations



Several sensors are used to control short

Several sensors are used to control short

circuit, turbulence, passivation, contact

circuit, turbulence, passivation, contact

and overcurrent sensors. In case of

and overcurrent sensors. In case of

contact, immense heat would be generated

contact, immense heat would be generated

melting the tool, evaporating the

melting the tool, evaporating the

electrolyte and cause a fire.

electrolyte and cause a fire.



The worker must be insulated to prevent

The worker must be insulated to prevent

electrocution.

electrocution.



The tool and the work piece must be

The tool and the work piece must be

grounded before any handling is

grounded before any handling is

performed.

performed.

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Safety Consideration

Safety Consideration



Hydrogen gas emitted is very flammable,

Hydrogen gas emitted is very flammable,

so it should be disposed of properly and

so it should be disposed of properly and

fire precautions should be taken.

fire precautions should be taken.



The waste material is very dangerous

The waste material is very dangerous

and environmentally unfriendly (metal

and environmentally unfriendly (metal

sludge) so it must be recycle or disposed

sludge) so it must be recycle or disposed

of properly.

of properly.



Electrolyte is highly pressurized and

Electrolyte is highly pressurized and

worker must check for minor cracks in

worker must check for minor cracks in

piping before operating.

piping before operating.

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Pulsed Electrochemical

Pulsed Electrochemical

Machining

Machining

A form of electrochemical machining;

A form of electrochemical machining;

the current is pulsed to eliminate the

the current is pulsed to eliminate the

need for high electrolyte flow

need for high electrolyte flow

Improves fatigue life of the part

Improves fatigue life of the part

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Electrochemical

Electrochemical

Grinding

Grinding

Uses a rotating cathode embedded with

Uses a rotating cathode embedded with

abrasive particles for applications

abrasive particles for applications

comparable to milling, grinding and

comparable to milling, grinding and

sawing

sawing

Most of the metal removal is done by the

Most of the metal removal is done by the

electrolyte, resulting in very low tool wear

electrolyte, resulting in very low tool wear

Adaptable for honing

Adaptable for honing

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Electrochemical

Electrochemical

Grinding

Grinding