MECHANICAL ENERGY BASED PROCESSES

1. RAMCO INSTITUTE OF TECHNOLOGY
Mr.M.LAKSHMANAN
Assistant Professor (Senior Grade)
Department of Mechanical Engineering

2. UNIT II
MECHANICAL ENERGY BASED
PROCESSES

3. Mechanical energy in the form of kinetic (Due
to Motion) or potential energy (Due to
Position).
• Abrasive Jet Machining (AJM)
• Water Jet Machining (WJM)
• Abrasive Water Jet Machining (AWJM)
• Ultrasonic Machining (USM)
• Abrasive Flow Finishing (AFF)
• Magnetic Abrasive Finishing (MAF)
• Abrasive Flow Machining (AFM)

4. Abrasive Jet Machining (AJM)/ Micro
Blast Machining
• Material is removed due to the action of a
high velocity stream of gas with small
abrasive particles.
• Mechanism of material removal is erosion
and chipping action.
• The jet of inert gas and abrasive particles
strike the work piece at high velocity (150 –
300 m/s)

5. It can be used for cutting, cleaning, etching,
polishing, deburring and trimming.
Principle of AJM

6. Schematic Diagram of AJM

7. Construction of AJM

12. Process Parameters
• Standoff distance or Nozzle tip Distance
• Abrasive Flow Rate
• Gas Pressure
• Mixing Ratio
• Abrasive Velocity
• Abrasive Grain Size

13. Standoff distance / Nozzle tip
Distance

14. Abrasive Flow Rate

16. Gas Pressure

17. Mixing Ratio

18. Abrasive Velocity

19. Abrasive Grain Size

21. Advantages of AJM
• Suitable for cutting all materials. Even
diamond can be machined by using
diamond as abrasive.
• No heat generation during this process. So,
thermal damage to the work piece is
avoided.
• Very thin and brittle materials can be cut
without any risk of breaking.
• It can be used to cut intricate hole shapes in
hard and brittle materials.

22. Disadvantages of AJM
• Material removal rate is slow
• Soft material cannot be machined
• Machining accuracy is poor
• Nozzle wear rate is high
• Abrasive powder used in this process
cannot be reused.

23. Application of AJM
• Machining of Quartz, ceramics, glass,
sapphire, etc.
• Fine drilling and micro welding
• Machining of semi conductors
• Cleaning and polishing of plastics, nylon and
Teflon components.
• Surface etching and surface preparation.

24. Characteristics of AJM
• Abrasive – Al2O3, SiC, Glass powder, Dolomite.
• Size – Around 25micrometer
• Flow Rate – 2-20g/min
• Medium – N2 / CO2
• Velocity – 125 – 300m/s
• Pressure – 2- 8 Kg/cm2
• Nozzle Material – Tungsten carbide(WC) /
Synthetic Sapphire
• Life of Nozzle – WC – 12 to 20 hrs,
Sapphire – 300hrs

25. • Nozzle tip Clearance – 0.25 to 15mm
• Tolerance - +/- 0.05mm
• Machining Operation – drilling, cutting,
deburring, cleaning, etc,.

26. Water Jet Machining (WJM)
• High pressure and high velocity stream of
water is used to cut the relatively soft and
non metallic materials like paper board,
wood, plastics, rubber, fibre glass, leather,
etc.

29. Process Parameters
• MRR
• Geometry and surface finish of work material
• Wear rate of nozzle

30. Material Removal Rate (MRR)
• MRR is directly proportional to the reactive
force(F) of the jet.
MRR α F
MRR α mxv
Where,
m – Mass flow rate
V – Jet Velocity

31. Geometry and surface finish of work
material
• Nozzle Design
• Jet velocity
• Cutting speed
• Depth of Cut
• Properties of materials

32. Wear rate of nozzle
• Hardness of the nozzle material
• Pressure of the jet
• Velocity of the jet
• Nozzle Design

33. Advantages
• Water is non toxic and easy to dispose
• Low operating cost
• Low maintenance cost
• The work area remains clean and dust free
• Very less amount of heat is generated during
cutting operation. So, there is no thermal
damage to the work.
• Low nozzle wear rate.

34. Disadvantages
• Initial cost of this process is high.
• Difficult to machine hard material.
• Noise operation.
Applications
• Cutting soft and non metallic materials.
• To cut intricate contours.
• Cutting of foods such as bread can also be
easily done with WJC.
• WJM in Aerospace, Architecture, Defense,
Marble and Tiles, etc.,

39. Recent Development in WJM/
Abrasive water Jet Machining(AWJM)

42. Characteristics of AWJM
• Work Material- Soft, Non Metallic materials like
Paper board, wood, plastics, rubber
• Tool – Water with additives
• Additives – Glycerin, polyethylene oxide
• Water Pressure – 100 to 1000MPa
• Mass flow rate – 8lit/min
• Power – 45KW
• MRR – 0.6 mm3/s
• Feed Rate – 1 to 4mm/s
• Nozzle Material – Tungsten Carbide, Synthetic
Sapphire
• Stand off Distance – 2 to 50 mm

45. Ultrasonic Machining (USM)
• Its one kind of grinding method. Its also known
as ultrasonic grinding or impact grinding.
• The sound wave frequency above the audible
range are known as Ultrasonic Waves.
• Its suitable for hard and brittle materials like
carbide, glass, Ceramics, silicon, Germanium,
titanium, Tungsten, Tool steels, etc.,

46. Principle
• A slurry of small abrasive particles are
forced against the work piece by means of a
vibrating tool and its causes the removal of
metal from the work piece in the form of
extremely small chips.

48. • The function of transducer is to convert the
electrical energy into mechanical energy.
• Ultrasonic oscillator and amplifier also known
as generator is used to convert the applied
electrical energy at low frequency to high
frequency.
• Abrasive slurry mixture of abrasive grains and
water of definite proportion 20-30 %.
• Gap Between tool and work piece 0.02 to
0.1mm.
• Abrasives are Boron Carbide (B4C), Silicon
carbide(SiC), Aluminium Oxide(Al2O3) and
Diamond.

49. Types of Transducer
• Magnetostriction Transducer
• Piezoelectric Transducer

50. Magnetostriction Effect

51. When a rod is Ferromagnetic material is kept
in a magnetic field parallel to its length, the
rod suffers a change in its length. The change
in length is independent of the direction of the
magnetic field and depends only on the
magnitude of the field and nature of material.
This phenonmenon is known as
“Magnetostriction Effect”.

52. Magnetostriction Transducer

53. Frequency of the Oscillatory Circuit =
Frequency of the Vibrating Rod
E- Youngs Modulus of the Rod material, N/m2
l – Langth of the Rod, m
P – Density of the Rod Material, Kg/m3.
C1 – Variable Capacitor

54. Advantages
• Production cost is low
• Very simple Design
• At low ultrasonic Frequencies, large power
output is possible without any damage to
the oscillatory circuit.

55. Disadvantages
• It cant produces ultrasonic waves of
frequency above 3000KHz.
• There will be losses of energy due to
hysteresis and eddy current.
• As frequency is inversely proportional to the
length of the rod, the length of the rod
should be decreased to increase the
frequency. Its practically not possible.

58. Piezoelectric Transducer
• Piezoelectric Transducer is more efficient than
Magnetostriction Transducer. The Modern
Ultrasonic Transducers are of this type.
Piezoelectric Effect
When mechanical force is applied to one pair of
opposite faces of certain crystals like quartz or
tourmaline equal and opposite electrical charges
appear across its other faces.
• But ultrasonic wave generation is based on
inverse piezoelectric effect.

59. Inverse Piezoelectric Effect
• When an AC voltage is applied across the
piezoelectric crystal, it starts vibrating at
the frequency of the applied voltage.

62. Advantages
• Its more efficient than Magnetostriction
Transducer.
• It can be produce frequency up to 500MHz.
• Its not affected by temperature and
humidity.
Disadvantages
• The cost of piezoelectric quartz is high and
the cutting and shaping of quartz crystal is
very complex.

64. Nodal Point Clamping

65. Feed Mechanism
• Gravity Feed Mechanism
• Spring Loaded Feed Mechanism.
• Pneumatic / Hydraulic Feed Mechanism.

66. Gravity Feed Mechanism

67. Spring Loaded Feed Mechanism

68. Pneumatic / Hydraulic Feed
Mechanism

69. Wear Ratio
Volume of material removed
Wear Ratio= from the work
Volume of Material eroded
from the tool

70. Factors Affecting MRR
• Grain size of Abrasive.
• Abrasive Materials.
• Concentration of Slurry.
• Amplitude of Vibration.
• Frequency of Ultrasonic Waves.

71. Grain size of Abrasive

72. Concentration of Slurry

73. Amplitude of Vibration

74. Frequency of Ultrasonic Waves

75. Process Parameters
• Metal Removal Rate
• Tool Material
• Tool Wear Rate
• Abrasive Materials and Abrasive Slurry
• Surface Finish
• Work Material

76. Tool Material
• Tough and ductile tool Material is used in
USM Process.
• Low carbon steels and stainless steels are
commonly used tool materials.
• Hollow tool can be made with wall thickness
greater than 0.5 to 0.8mm.
• Side clearance to the tool is of the order of
0.06 to 0.36mm depending on grain size of
abrasive.

77. Tool Wear Rate
The wear ratios are
1.5:1 for Tungsten Carbide
100:1 for Glass
50:1 for Quartz
75:1 for Ceramics
1:1 for Hardened Tool Steel

78. Abrasive Materials and Abrasive Slurry

79. Surface Finish
Accuracy of this process is +/- 0.006mm and
surface finish upto 0.02 to 0.8 micron Value
can be achieved.

80. Work Material

82. Advantages of USM
• Cost of metal removal is low.
• Noiseless operation.
• Equipment is safe to operate.
• There is no heat generation in this process. So
the physical properties of the work material
remain unchanged.
• Non conducting materials of electricity can be
easily machined.

83. Disadvantages
• Metal removal rate is low.
• Softer materials are difficult to machine.
• Wear rate of the tool is high.
• The initial equipment cost is high.
• High power consumption.
• Tool cost is high.

84. Applications of USM
• Holes as small as 0.1mm can be drilled.
• precise and intricate shaped articles can be
machined.
• Its used for making Tungsten Carbide and
Diamond wire drawing dies and dies for
forging and extrusion process.