UNIT-I INTRODUCTION AND ULTRASONIC MACHINING

1
UNIT-IINTRODUCTION AND ULTRASONIC MACHINING

• Subject Non-Traditional Machining (ME 635)
• N.RAM KUMAR M.E.,
• ASSISTANT PROFESSOR
• DEPARTMENT OF MECHANICAL ENGINEERING
• CHRIST UNIVERSITY FACULTY OF ENGINEERING
• BANGALORE

2
SYLLABUS

• UNIT 1
  
  13 Hours
• INTRODUCTION History, Classification, comparison
  between conventional and Nonconventional
  machining process selection.
• ULTRASONIC MACHINING (USM) Introduction,
  equipment, tool materials tool size, abrasive
  slurry, cutting tool system design- Effect of
  parameter Effect of amplitude and frequency and
  vibration, Effect of abrasive grain diameter,
  effect of applied static load, effect of slurry,
  tool work material, USM process
  characteristics Material removal rate, tool
  wear, Accuracy, surface finish, applications,
  advantages Disadvantages of USM.
• UNIT 2
  
  11 Hours
• ABRASIVE JET MACHINING (AJM) Introduction,
  Equipment, Variables in AJM Carrier Gas, Type of
  abrasive, size of abrasive grain, velocity of the
  abrasive jet, mean number. Abrasive particles per
  unit volume of the carrier gas, work material,
  stand off distance (SOD), nozzle design, shape of
  cut. Process characteristics-Material removal
  rate, Nozzle wear, Accuracy surface finish.
  Applications, advantages Disadvantages of AJM.
• Water Jet Machining Principle, Equipment,
  Operation, Application, Advantages and
  limitations of water Jet machinery

3
SYLLABUS

• UNIT 3
  
  12 Hours
  
  ELECTROCHEMICAL
  MACHINING (ECM) Introduction, study of ECM
  machine, Elements of ECM process
  Cathode tool, Anode work piece, source of DC
  power, Electrolyte, Chemistry of the process, ECM
  Process characteristics Material removal rate,
  Accuracy, surface finish, ECM Tooling ECM
  tooling technique example, Tool insulation
  materials, Tool size Electrolyte flow
  arrangement, Handling of slug, Economics of ECM,
  Applications such as Electrochemical turning,
  Electrochemical Grinding, Electrochemical Honing,
  deburring, Advantages, Limitations.
• CHEMICAL MACHINING (CHM) Introduction, elements
  of process Preparation of work piece,
  preparation of masters, masking with photo
  resists, etching for blanking, accuracy of
  chemical blanking, applications of chemical
  blanking, chemical milling (contour machining)
  process steps masking, Etching, Process
  characteristics of CHM material removal rate,
  accuracy, surface finish, Hydrogen embrittlement,
  advantages application of CHM.

4
SYLLABUS

• UNIT - 4
  
  11 Hours
  ELECTRICAL DISCHARGE MACHINING (EDM)
  Introduction, mechanism of metal removal,
  dielectric fluid, spark generator, EDM tools
  (electrodes) Electrode feed control, Electrode
  manufacture, Electrode wear, EDM tool design,
  choice of machining operation, electrode material
  selection, under sizing and length of electrode,
  machining time. Flushing pressure flushing,
  suction flushing, side flushing, pulsed flushing
  synchronized with electrode movement, EDM process
  characteristics metal removal rate, accuracy,
  surface finish, Heat Affected Zone. Machine tool
  selection, Application, EDM accessories /
  applications, electrical discharge grinding,
  Traveling wire EDM.
• UNIT 5
  
  13
  Hours
• PLASMA ARC MACHINING (PAM) Introduction,
  equipment, non-thermal generation of plasma,
  selection of gas, Mechanism of metal removal, PAM
  parameters, process characteristics. Safety
  precautions, Applications, Advantages and
  limitations.
• LASER BEAM MACHINING (LBM) Introduction,
  equipment of LBM mechanism of metal removal, LBM
  parameters, Process characteristics,
  Applications, Advantages limitations.
• ELECTRON BEAM MACHINING (EBM) Principles,
  equipment, operations, applications, advantages
  and limitation of EBM.

5
INTRODUCTION

• What is Engineering?
• Engineering (from Latin ingenium, meaning
  "cleverness" and ingeniare, meaning "to contrive,
  devise") is the application of scientific,
  economic, social, and practical knowledge in
  order to invent, design, build, maintain, and
  improve structures, machines, devices, systems,
  materials and processes.
• Engineering is the Study of Design and working of
  any system.

6
INTRODUCTION

• What is Mechanical Engineering?
• Mechanical Engineering is one of the major
  activities in the engineering profession and its
  principles are involved in the design, study,
  development and construction of nearly all of the
  physical devices and systems.

7
INTRODUCTION
8
INTRODUCTION

• What is Manufacturing?

9
INTRODUCTION

• Types of Manufacturing Processes
• Manufacturing processes can be broadly divided
  into two groups
• Primary manufacturing processes
• Secondary manufacturing processes.
• The Primary manufacturing process provides basic
  shape and size to the material as per designers
  requirement. For example Casting, forming,
  powder metallurgy processes provide the basic
  shape and size.
• The Secondary manufacturing processes provide the
  final shape and size with tighter control on
  dimension, surface characteristics etc. Most of
  Material removal processes are mainly the
  secondary manufacturing processes.

10
INTRODUCTION

• Material removal processes can be further divided
  into mainly two groups
• 1. Conventional Machining Processes
• 2. Non-Traditional Manufacturing Processes
• Examples of conventional machining processes are
  turning, boring, milling, shaping,
• broaching, slotting, grinding etc.
• Examples of non conventional ( or also called non
  traditional or unconventional) are
• Abrasive Jet Machining (AJM),
• Ultrasonic Machining (USM),
• Water Jet and Abrasive Water Jet Machining (WJM
  and AWJM),
• Electro-discharge Machining (EDM) ,
• Electro Chemical Machining (ECM).

11
CONVENTIONAL MACHINING PROCESS

• Generally macroscopic chip formation by shear
  deformation
• Material removal takes place due to application
  of cutting forces energy domain can be
  classified as mechanical
• Cutting tool is harder than work piece at room
  temperature as well as under machining conditions
  

12
CONVENTIONAL MACHINING PROCESS
13
COMPARISON
Conventional Non Conventional
Chip Formation Generally macroscopic chip formation by shear deformation. Material removal may occur with chip formation or even no chip formation may take place. For example in AJM, chips are of microscopic size and in case of Electrochemical machining material removal occurs due to electrochemical dissolution at atomic level
Tool There may be a physical tool present. for example a cutting tool in a Lathe Machine,   There may not be a physical tool present. For example in laser jet machining, machining is carried out by laser beam. However in Electrochemical Machining there is a physical tool that is very much required for machining.




14
Conventional Non Conventional
Characteristic of Tool Cutting tool is harder than work piece at room temperature as well as under machining conditions   There may not be a physical tool present. For example in laser jet machining, machining is carried out by laser beam. However in Electrochemical Machining there is a physical tool that is very much required for machining.
Material Removal Process Material removal takes place due to application of cutting forces energy domain can be classified as mechanical   Mostly NTM processes do not necessarily use mechanical energy to provide material removal. They use different energy domains to provide machining. For example, in USM, AJM, WJM mechanical energy is used to machine material, whereas in ECM electrochemical dissolution constitutes material removal.
15
Conventional Non Conventional
Tool Contact Conventional machining involves the direct contact of tool and work piece   Whereas unconventional machining does not require the direct contact of tool and work piece.
Surface Finish Lower accuracy and surface finish. Higher accuracy and surface finish.
16
Conventional Non Conventional
Material Economy Suitable for every type of material economically. Not Suitable for every type of material economically
Tool Life Tool life is less due to high surface contact and wear. Tool life is more
Material Wastage Higher waste of material due to high wear. Lower waste of material due to low or no wear.
Noise Level Noisy operation mostly cause sound pollutions Quieter operation mostly no sound pollutions are produced.
Cost Lower capital cost Higher Capital Cost
17
Conventional Non Conventional
Equipment Setup   Easy set-up of equipment. Complex set-up equipment.
Operator level Skilled or un-skilled operator may required Skilled operator required.
Process Generally they are manual to operate. Generally they are fully automated process.
Efficiency They cannot be used to produce prototype parts very efficiently and economically. Can be used to produce prototype parts very efficiently And economically.
Spare Parts Easily Available Not so easily available
18
ULTRASONIC MACHINING

• Introduction.
• Equipment.
• Tool Materials and Tool Size and Abrasive Slurry.
  
• Cutting tool system design
• Effect of parameter Effect of amplitude and
  frequency and vibration.
• Effect of abrasive grain diameter.
• Effect of applied static load.
• Effect of slurry, tool and work material.
• USM process characteristics Material removal
  rate, tool wear, Accuracy, surface finish,
  applications,
• Advantages Disadvantages of USM.

19
INTRODUCTION

• What is the Difference between Frequency,
  Wavelength and Amplitude?
• Frequency tells us how many waves pass through a
  point at a second.
• Wavelength tells us the length of those waves.
• Amplitude tells us how big the wave is.
• In USM, abrasives contained in a slurry are
  driven against the work by a tool oscillating at
  low amplitude (25-100 microns) and high frequency
  (15-30 kHz).

20
PRINCIPLE

• The machining zone (between the tool and the work
  piece) is flooded with hard abrasive particles
  generally in the form of water based slurry.
• As the tool vibrates over the work piece,
  abrasive particles acts as indenter and indent
  both work and tool material .
• Abrasive particles , as they indent , the work
  material would remove the material from both tool
  and work piece.
• In Ultrasonic machining material removal is due
  to crack initiation, propagation and brittle
  fracture of material.

21
EQUIPMENT
22
EQUIPMENT

• Ultrasonic Machining consists of
• High Power sine wave generator.
• Magneto-strictive Transducer.
• Tool Holder.
• Tool.

23
(No Transcript)
24
High Power Sine Wave Generator

• This unit converts low frequency (50 Hz)
  electrical power to high frequency (20kHz)
  electrical power.

25
TRANSDUCER

• The high frequency electrical signal is
  transmitted to traducer which converts it into
  high frequency low amplitude vibration.
• Essentially transducer converts electrical energy
  to mechanical vibration. There are two types of
  transducer used
• 1. Piezo electric transducer
• 2. Magneto-stricitve transducer.

26
MAGNETOSTRICTIVE TRANSDUCER

• These transducer are made of nickel , nickel
  alloy sheets.
• Their conversion efficiency is about 20-30.
• Such transducers are available up to 2000 Watts.
• The maximum change in length can be achieved is
  about 25 microns.

27
TOOL HOLDER OR HORN

• The tool holder holds and connects the tool to
  the transducer. It virtually transmits the energy
  and in some cases, amplifies the amplitude of
  vibration.
• Material of tool should have good acoustic
  properties, high resistance to fatigue cracking.
• Due measures should be taken to avoid ultrasonic
  welding between transducer and tool holder.
• Commonly used tool holders are Monel, titanium,
  stainless steel.
• Tool holders are more expensive, demand higher
  operating cost.

28
TOOL

• Tools are made of relatively ductile materials
  like Brass, Stainless steel or Mild steel so that
  Tool wear rate (TWR) can be minimized.
• The value of ratio of TWR and MRR depends on kind
  of abrasive, work material and tool materials.

29
Mechanism of Material Removal
30
Material Removal Models in USM

• The following are the Material Removal Models
  used in USM
• 1. Throwing of abrasive grains.
• 2. Hammering of abrasive grains.
• 3. Cavitations in the fluid medium arising out of
  ultrasonic vibration of tool.
• 4. Chemical erosion due to micro agitations.

31
(No Transcript)
32
(No Transcript)
33
Effect of Slurry, Tool and Work Material

• MRR increases with slurry concentration.
• Slurry saturation occurs at 30 to 40
  abrasive/water mixture.
• Material Removal rate drops with increasing
  viscosity.
• The pressure with which the slurry is fed into
  the cutting zone affects MRR .
• In some cases MRR can be increased even ten
  times by supplying the slurry at increased
  pressure.
• The shape of the tool affects the MRR. Narrower
  rectangular tool gives more MRR compared to
  square cross section.

34

• Conical tool gives twice MRR compared to
  cylindrical tool.
• The brittle behavior of material is important in
  determining the MRR.
• Brittle material can be cut at higher rates than
  ductile materials.

35
APPLICATIONS

• Machining of cavities in electrically
  non-conductive ceramics
• Used to machine fragile components in which
  otherwise the scrap rate is high
• Used for multistep processing for fabricating
  silicon nitride (Si3N4) turbine blades
• Large number of holes of small diameter could be
  machined. 930 holes with 0.32mm has been reported
  ( Benedict, 1973) using hypodermic needles
• Used for machining hard, brittle metallic alloys,
  semiconductors, glass, ceramics, carbides etc.

36

• Used for machining round, square, irregular
  shaped holes and surface impressions.
• Used in machining of dies for wire drawing,
  punching and blanking operations
• USM can perform machining operations like
  drilling, grinding and milling operations on all
  materials which can be treated suitably with
  abrasives.
• USM has been used for piercing of dies and for
  parting off and blanking operations.
• USM enables a dentist to drill a hole of any
  shape on teeth without any pain

37

• Ferrites and steel parts , precision mineral
  stones can be machined using USM
• USM can be used to cut industrial diamonds
• USM is used for grinding Quartz, Glass, ceramics
• Cutting holes with curved or spiral centre lines
  and cutting threads in glass and mineral or
  metallo-ceramics.

38
ADVANTAGES

• It can be used machine hard, brittle, fragile and
  non conductive material
• No heat is generated in work, therefore no
  significant changes in physical structure of work
  material
• Non-metal (because of the poor electrical
  conductivity) that cannot be machined by EDM and
  ECM can very well be machined by USM.
• It is burr less and distortion less processes.
• It can be adopted in conjunction with other new
  technologies like EDM,ECG,ECM.

39
DISADVANTAGES

• Low Metal removal rate.
• It is difficult to drill deep holes, as slurry
  movement is restricted.
• Tool wear rate is high due to abrasive particles.
  Tools made from brass, tungsten carbide, MS or
  tool steel will wear from the action of abrasive
  grit with a ratio that ranges from 11 to 2001.
• USM can be used only when the hardness of work is
  more than 45 HRC.

40
BEST OF LUCK
41
THANK YOU