Conventional or Non-Conventional Machining

Machining

It is defined as, "a manufacturing process which creates desired shape by removing unwanted material from a larger piece material".

• Conventional Machining  ↔  Machining in which there is a direct contact between material and tool.
• Non-conventional Machining  ↔  No direct contact between material and tool.

Non-Conventional Machining

Following are the types of non-conventional machining.

1. Electric Discharge Machining (Spark Erosion or Thermal Erosion or Electro-Erosion or Spark Machining Process or EDM)

Technique which uses thermo-electric process to erode undesired material from workpiece is called Electric Discharge Machining.

• Tool is negative terminal whereas workpiece is positive terminal.
• Spark Gap  ↔  distance between work and tool and is filled by dielectric fluid.

Application:

• Drilling of very small holes.
• Milling of machine complex shapes.

2. Wire Cut EDM

• Wire of about (0.02 - 0.03) mm in diameter is used which is made of brass, copper, tungsten, zinc or brass coated wire (high tensile strength and good electrical conductivity).
• Removed particles flushed away by flowing dielectric fluids.

Advantages:

• Smooth machine surface and polishing is not required.
• Wear of electrode is negligible.

Application:

• Intricate components for electrical and aerospace industries.
• Machining of sheet metal die, extrusion dies and prototype parts.
• High precision in cutting cylindrical objects.

3. Laser Beam Machining (LBM)

It is defined as, "a thermal metal removal process which uses laser beam to melt and vaporize particles on the surface of metallic and non-metallic workpiece".

• Ruby (Al2O3) with 0.05 % Cr
• One end  ↔  blocked with total reflective mirror.
• Other end  ↔  having partially reflected mirror.
• Flash Tube  ↔  placed outside ruby crystal.

Construction:

1. Cylindrical Crystal Ruby Tube
2. Flash Tube
3. Focusing Lens
4. Power Supply Source
5. Total and Partial Reflecting Mirror 
6. Cooling System

Advantages:

• Dissimilar material welding 
• Accuracy is high and does not require filler material.

Application:

• Laser drilling, metal cutting, welding, etc.
• Aerospace and automobile industries.

4. Electron Beam Machining (EBM)

It is defined as, "high velocity electron beam emitted from tungsten filament for the removal of material".

• Electron gun  ↔  grid up, tungsten filament (cathode), anode.
• The filament and anode are connected with DC power supply.

Construction:

1. Vacuum chamber
2. Electron gun
3. Magnetic lens (to focus beam)
4. Deflecting coil
5. Work table for holding

Application:

• Drilling of holes in pressure differential device.
• Machining of low thermal conductive and high melting point materials.

5. Electrochemical Machining (ECM)

It is defined as, "metal removal process based on the principle of reverse electroplating".

• Tool is negative terminal and workpiece is positive terminal.
• Work material oxidized  ↔  machined by using current passing through electrolyte.

Application:

• Machining of turbine blades.

6. Electrochemical Grinding (Electrolytic Grinding or Anodic Machining or ECG)

It is defined as, "combination of conventional mechanical grinding and electrochemical machining in which material removed by electrolytic activity".

• Material removed by electrochemical decomposition and remaining material is removed by abrasion of material metal.

Construction:

1. Cathode (metallic grinding wheel)
2. Anode (workpiece)
3. Electrolyte tank
4. Circulation system
5. Electrolyte (non-corrosive salt solution is used with water).

Advantage:

• Not suitable for soft materials.

Applications:

• For grinding carbide tools
• Refractory metals
• Cobalt based alloy

7. Plasma Arc Machining (PAM)

It is defined as, "cutting of metal with arc of plasma (jet of high velocity ionized gas) that removes material from work piece".

Construction:

1. Plasma torch (gas chamber, nozzle which is anode)
2. Tungsten electrode which is cathode
3. Power supply
4. Argon, nitrogen, hydrogen, compressed air introduced around cathode.

Advantages:

• High cutting rate
• No surface preparation requirements
• Produce tapered surface

8. Chemical Machining (CM)

It is a metal machining process which uses chemical dissolution (chemical agents or etchants) which can be acids or alkaline solutions.

Work Surface + Etchants  →  Removal of material from surface due to chemical reaction

Classification of chemical machining:

1. Chemical Blanking 
2. Chemical Milling 
3. Chemical Engraving 

Steps for Chemical Machining 

1. Residual stress relieving 
2. Cleaning the work piece 
3. Masking 
4. Etching 
5. De-making 

Application: 

• Aerospace industry to remove shallow layers of material from large aircraft components (like missile skin panels and airframe parts).

9. Ultrasonic Grinding (or Ultrasonic Machining or Ultrasonic Impact Grinding or USM)

It is defined as, "a material removal process in which material is removed by repetitive impact of abrasive slurry on work surface by using high frequency oscillation of shaped tool".

• Abrasive Slurry  ↔  mixture of abrasive grains and carrier fluid provided between tool and work piece.
• Carrier fluid  ↔  water.

Construction:

1. Ultrasonic generator 
2. Transducer
3. Concentrator 
4. Tool
5. Abrasive slurry and its feed mechanism 
6. Tool feed mechanism 

Applications:

• Machining hard/brittle material like ceramics, boron carbide, titanium carbide.
• Dentist  ↔  drill hole on teeth painlessly.

10. Abrasive Jet Machining (or Micro-Abrasive Blasting or AJM)

It is defined as, "Mechanical energy based unconventional machining process used to remove unwanted material from a given workpiece".

• Nozzle  ↔  hard material (like tungsten carbide)
• Abrasive  ↔  Al2O3, SiC, Na2CO3.
• Gases  ↔  N2, carbon dioxide, air.

Factors Affecting Performance of AJM

1. Abrasive grain size and its mass flow rate.
2. Mixing ratio
3. Velocity of abrasive particles
4. Gas pressure 
5. Nozzle tip distance

Advantage:

• No heat is generated

Applications:

• Drilling, cleaning, polishing of hard surface.
• Machine intricate shape.
• Aircraft fuel system, hydraulic valves.

References:

• Material from Class Lectures + Book named Fundamentals of Modern Manufacturing Materials, Processes and Systems by Groover + My knowledge. 
• Photoshoped pics are developed. 
• Some pics and GIF from Google.  
• Videos from YouTube (Engineering Sights).