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ELECTRO CHEMICAL MACHINING

SUBMITTED BY:Rajneesh Kumar

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CONTENT: Non-Traditional Machining

Classification of Non-traditional Machining Processes Electrochemical Machining (ECM)

What is Electroplating? Electrochemical Machining History

Tool Material Schematic diagram

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Non-Traditional Machining

Need :

• To machine newly developed metals and non-metals

• To machine complex part geometries

• To avoid surface damage

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Classification of Non-traditional Machining Processes

This classification is carried out depending on nature of energy used for material removal:

Mechanical Thermo- Chemical

Electro electricElectrochemical

• USM• AJM•WJM• AWJM

• EDM• EBM• LBM• PAM

• CHM• PCM

• ECG• EJD• ECM

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Electrochemical Machining (ECM)

• Electrochemical machining (ECM) is an electrolytic material removal process involving a negatively charged shaped electrode (cathode), a conductive fluid (electrolyte), and a conductive work piece (anode).

• ECM is characterized as "reverse electroplating."  The tool must be properly shaped, and provision for waste removal must be made.

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What is Electroplating?

An electrochemical process where metal ions are transferred from a solution and are deposited as a thin layer onto surface of a cathode.

The setup is composed DC circuit with an anode and a cathode sitting in a bath of solution that has the metal ions necessary for coating or plating

Electroplating can enhance;Chemical properties---increase corrosion resistancePhysical properties---increase thickness of partMechanical properties---increase tensile strength & hardness

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How it works

Copper Cathode is reduced(accepts electrons)

Nickel Anode is oxidized(gives us electrons)

Ni2+ ions within solution become attracted to Copper cathode

Electrochemical Machining

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Electrochemical Machining History

• Electrochemical machining (ECM) has been developed initially to machine these hard to machine alloys, although any metal can so be machined.

• ECM is an electrolytic process and its basis is the phenomenon of electrolysis, whose laws were established by Faraday in 1833.

• The first significant developments occurred in the

1950s, when ECM was investigated as a method for shaping high strength alloys.

• As of the 1990s, ECM is employed in many ways, for example, by automotive, offshore petroleum, and medical engineering industries, as well as by aerospace firms, which are its principal user.

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Working Principle

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Tool Material

•The tool is typically made of• copper,• brass, or •stainless steel, •while the most commonly used electrolyte is a concentrated solution of inorganic salts, such as sodium chloride, and the direct current power source is low voltage and high ampere.

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Schematic diagram

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ECM Components (Power)•The power needed to operate the ECM is obviously electrical. There are many specifications to this power.

•The current density must be high.

•The gap between the tool and the work piece must be low for higher accuracy, thus the voltage must be low to avoid a short circuit. •The control system uses some of this electrical power.

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ECM Components (electrolyte circulation system)

•The electrolyte must be injected in the gap at high speed (between 1500 to 3000 m/min).

•The inlet pressure must be between 0.15-3 MPa.

•The electrolyte system must include a fairly strong pump.

•System also includes a filter, sludge removal system, and treatment units.

•The electrolyte is stored in a tank.

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ECM Components (control system)• Control parameters include:

VoltageInlet and outlet pressure of electrolyteTemperature of electrolyte.

• The current is dependent on the above parameters and the feed rate.

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Advantage• Components are not subject to either thermal or

mechanical stress. There is no tool wear in ECM.

• Non-rigid and open work pieces can be machined easily as there is no contact between the tool and work piece.

• Complex geometrical shapes can be machined repeatedly and accurately

• ECM is a time saving process when compared with conventional machining

• During drilling, deep holes can be made or several holes at once.

Surface finishes of 25 µ (micron) can be achieved in ECM.

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Disadvantage• More expensive than conventional machining.

• Need more area for installation.

• Electrolytes may destroy the equipment.

• Not environmentally friendly (sludge and other waste)

• High energy consumption.

• Material has to be electrically conductive.

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Applications

• Die-sinking operations

• Drilling jet engine turbine blades

• Multiple hole drilling

• Machining steam turbine blades within close limits

• jet engines

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Products• The two most common products of ECM are turbine/compressor blades

and rifle barrels. Each of those parts require machining of extremely hard metals with certain mechanical specifications that would be really difficult to perform on conventional machines.

• Some of these mechanical characteristics achieved by ECM are:

Stress free grooves. Any groove geometry. Any conductive metal can be machined. Repeatable accuracy of 0.005”. High surface finish. Fast cycle time.

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