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Electrochemical Electrochemical Machining Machining

(ECM)(ECM)Dr. Lotfi K. GaafarDr. Lotfi K. Gaafar

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Electrochemical Electrochemical MachiningMachining

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Electrochemical Electrochemical MachiningMachiningUses an electrolyte and electrical current to Uses an electrolyte and electrical current to

ionize and remove metal atomsionize and remove metal atoms

Can machine complex cavities in high-Can machine complex cavities in high-strength materialsstrength materials

Leaves a burr-free surfaceLeaves a burr-free surface

Not affected by the strength, hardness or Not affected by the strength, hardness or toughness of the materialtoughness of the material

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Electrochemical Electrochemical MachiningMachining

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Operating PrincipleOperating 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 sinkingelectrochemical sinking

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Operating PrincipleOperating 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 PrincipleOperating 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 SubsystemsMain 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: VoltageVoltage Inlet and outlet pressure of electrolyteInlet 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 systemof the machine system

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AdvantagesAdvantages 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 fastRelatively fast Can machine harder metals than the Can machine harder metals than the

tool.tool.

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Advantages over EDMAdvantages over EDM Faster than EDMFaster 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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DisadvantagesDisadvantages 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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ApplicationsApplications 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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EconomicsEconomics 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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ProductsProducts 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 ConsiderationsSafety 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 contact, immense heat would be generated melting the tool, evaporating generated melting the tool, evaporating the electrolyte and cause a fire. the 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 ConsiderationSafety 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 MachiningMachining

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 flowneed for high electrolyte flow

Improves fatigue life of the partImproves fatigue life of the part

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Electrochemical Electrochemical GrindingGrinding

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 sawingsawing

Most of the metal removal is done by the Most of the metal removal is done by the electrolyte, resulting in very low tool wearelectrolyte, resulting in very low tool wear

Adaptable for honingAdaptable for honing

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Electrochemical Electrochemical GrindingGrinding