Working principle of various non conventional machining processes

 TABLE OF CONTENTS

1. Ultrasonic Machining – USM

2. Chemical Machining – CM

3. Electro Chemical Machining – ECM

4. Electro Chemical Grinding – ECG

5. Electrical Discharge Machining – EDM

6. Plasma Arc Machining – PAM

7. Laser Beam Machining – LBM

The various unconventional machining process are listed below.

Ultrasonic Machining – USM

Chemical Machining – CM

Electro Chemical Machining – ECM

Electro Chemical Grinding – ECG

Electrical Discharge Machining – EDM

Plasma Arc Machining – PAM

Laser Beam Machining – LBM

1. ULTASONIC MACHINING (USM)

 

• The main parts are generator, transducer, tool holder, table, power supply.
• Generator converts the low frequency (50 HZ) to high frequency (20,000 HZ) current.
• Transducer converts this high frequency current into mechanical vibrations.
• This mechanical vibrations are transmitted to the tool holder.
• Tool holder contains the tool to machine the work piece.
• During the vibration, tool vibrates along the work piece.
• During the tool vibration abrasive slurry is applied between the tool and work piece. 
• Abrasive slurry is a mixture of the abrasive particle and water.
• These abrasive particles are used to remove the material on the work piece.

Advantages of Ultrasonic machining process

• Less skilled labor.
• Low production cost
• It can be used to machine complex shape.

Disadvantages of ultrasonic machining process

• It consumes high electric current
• Not suitable for remove of excess metal particles.

Applications of ultrasonic machining process

• It is used to make holes in brittle materials like glass, diamonds and ceramics.
• This method is used to machine conducting and non-conducting materials.

2. CHEMICAL MACHINING (CM)

 

• Also known as chemical milling.
• CM consists of Cleaning, Masking, Etching and Demasking.
• Cleaning – Initially the work piece will be cleaned using solvent.
• After the cleaning it is washed and also it is dried.
• Masking – it is the process of covering the portion of work piece which are not to be machined.
• Normally rubber sheet is used for masking.
• Etching – After the masking, the work piece is immersed in a hot chemical.
• These chemical is called as the enchant. 
• Different enchant are used according to the work piece.
• Acids are used for steel. Ex. H2 SO4
• These acid converts the metal into metal salts.
• Ex. Fe →Fe2 SO4
• The metal removal rate depends on the concentration of enchant and the temperature.
• The MRR is high, when the concentration and temperature of enchant is high.
• The MRR is low, when the concentration and temperature of enchant is low.
• Demasking – After the etching the work piece is taken out from the enchant.
• Then it is cleaned in water and masking sheet is removed.

Advantages of chemical machining process

• Less skilled operator.
• This process is suitable for all type of metals.
• The rate of metal removal can be controlled easily.
• The metal can be removed uniformly.
• All sides of work piece can be machined at same time.

Disadvantages of chemical machining process

• It is a slow process.
• It is not suitable to remove large metal particles.
• Chemicals are injuries to health.

Applications of chemical machining process

• It can be used to machine irregular shape.
• Thin metal sheets are removed.
• Automobile parts and air craft parts are machined.

3. ELECTRO CHEMICAL MACHINING (ECM)

 

• It is a reversible process of electro plating process.
• The work piece is fitted in a fixture inside a tank.
• Tank consists of electrolyte.
• Generally sodium chloride or sodium nitrate is used as electrolyte.
• Work piece is immersed in this electrolyte.
• Positive terminal is connected with the work piece.
• Negative terminal is connected with the tool.
• During the process, electrolyte will be circulated by the pump.
• When DC supply is given, the electrons are released from the work piece.
• These electrons are carried away by the fast flowing electrolyte.
• Due to this action metal particles are removed from the work piece.
• Metal removal depends on the amount of current passes through the circuit.

Advantages of electro chemical  machining process

• Simple and fast process.
• Good surface finish.
• Complex shapes are machined easily.
• No tool wear.
• Suitable for all metals.
• Rate of removal is more.

Disadvantages of electro chemical  machining process

• High electric power is needed.
• Not suitable for non-conducting materials.
• Costly.
• Corrosion may occurs due to electrolyte.

Applications of electro chemical machining process

• Complex and Irregular shapes are machined easily.
• Gas turbine blades, impeller and air craft parts are machined.

4. ELECTRO CHEMICAL GRINDING (ECM)

 

• In this method, metal is removed by both electro chemical and grinding processes..
• Grinding process removes metal only 10 %.
• 90% of metal removal can be done by the electro chemical process.
• Grinding wheel is attached in the spindle. Spindle is used to rotate the grinding wheel.
• Work piece is connected to positive terminal. And the tool is connected to the negative terminal.mm gap is maintained during the process.
• An electrolyte is passed between this gap.
• Sodium chloride and sodium nitrate is used as a electrolyte.
• Electrolyte also act as a coolant. It is filtered and recirculated.
• When the power supply is given, the metal is removed by the electro chemical process.
• Some amount of metal is removed by the grinding process.
• Removed particles are carried by the electrolyte.

Advantages of electro chemical grinding process

• Fast process.
• Very hard materials are removed.
• Rate of metal removal is high.

Disadvantages of electro chemical grinding process

• Suitable only for conducting materials.
• High electric power is required.
• High investment.
• Not suitable for complicated shapes.
• Corrosion may occurs due to electrolyte.

5. ELECTRICAL DISCHARGE MACHINING (EDM)

• In this process metal is removed by the erosion.
• Work piece is held in the dielectric fluid.
• Positive terminal is connected with the work piece.
• Negative terminal is connected with the tool.
• Tool is used as a hollow. And it is made by copper or brass.
• Dielectric fluid is passed in the tool pipe.
• 0.005 mm to 0.05 mm gap is maintained between the work piece and tool.
• When the DC supply is given electric spark is produced in this gap.
• And High heat (12000C) is produced.
• Small area of the material is melted by this heat.
• Molten metal is spitted into small particles.
• These particles are carried away by the dielectric fluid.
• Dielectric fluid also act as a coolant.

Advantages of electrical discharge machining process

• Fast process.
• Conductive materials can be machined.
• Complex and irregular surfaces can be machined.

Disadvantages of electrical discharge  machining process

• High electric power is needed.
• Suitable only for conductive material.
• Square corners cannot be formed.

Applications of electrical discharge machining process

• Used to make small holes in nozzles.
• It is used to machine hard and brittle materials.
• It is used to cutting off the work piece.
• It is used to sharpening the tool and cutters.

6. PLASMA ARC MACHINING (PAM)

 

• The ionized gas is called as plasma.
• When the gas is heated to a very high temperature it gets ionized.
• Metal is removed by passing this plasma on the surface work piece at high velocity.
• H2 or N2 gas is passed through the gas chamber.at high speed.
• Nozzle is provided at the bottom of the gas chamber.
• Tungsten electrode is fitted in the gas chamber.
• Electrode is connected with negative terminal.
• Nozzle and work piece are connected with the positive terminal.
• When DC supply is given, electric spark will be produced between the electrode and nozzle.
• Due to this gas will be ionized.
• Plasma is forced on the work piece through the nozzle.
• Metal is melted due to this plasma.
• And the melted materials are removed by the high velocity of plasma.

Advantages of plasma arc machining process

• Fast process.
• All metals are machined.
• Material can be machined up to 150 mm thick.

Disadvantages of plasma arc machining process

• Less surface finish.
• Less accuracy.
• High electrical power is required.
• Costly.
• UV and IR radiation affect the worker’s health.

Applications of plasma arc machining process

• Used to cutting Stainless steel and aluminium alloys.
• Used for cutting required profile in alloys. 

7. LASER BEAM MACHINING (LBM)

 

• Light Amplification by Simulated Emission of Radiation is called as LASER.
• It is a light beam having some wavelength.
• When the laser is focused by the lens, the metal is melted and vaporized due to the high temperature.
• The equipment has a ruby laser.
• It is placed inside the flash lamp.
• Flash lamp is filled with the xeon gas.
• When the power supply is given flash lamp gives light to the ruby crystal.
• Then the laser is stimulated and emitted by the ruby crystal.
• Laser is focused by the lens on the work piece.
• Due to this high temperature can be produced in the work piece.
• Then the metal is melted and vaporized.

Advantages of laser beam machining process

• Suitable for all metals.
• High accuracy.
• No force acts on the work piece.
• Metals and nonmetals can be machined.
• Curved and angular machining can be done easily.

Disadvantages of laser beam  machining process

• High equipment cost.
• Life of flash lamp is short.
• Large amount of metal cannot be removed.

Applications of  laser beam  machining process

• It is used for producing very fine and minute holes. (0.005 mm dia)
• It is used to produce holes in surgical needles.
• It is used to make holes in hard in brittle materials.