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Regulation 2008ME2026 UNCONVENTIONAL MACHINING

PROCESSES(Common to Mechanical and Production)

UNIT I Introduction (5)Unconventional machining Process – Need – classification –

Brief overview .

UNIT II Mechanical Energy Based Processes (10)Abrasive Jet Machining – Water Jet Machining – Abrasive

Water Jet Machining - Ultrasonic Machining. (AJM, WJM, AWJMand USM). Working Principles – equipment used – Processparameters – MRR-Variation in techniques used – Applications.

UNIT III Electrical Energy Based Processes (8)Electric Discharge Machining (EDM)- working

Principle-equipments-Process, Parameters-Surface Finish and MRR-electrode / Tool – Power and control Circuits-ToolWear – Dielectric– Flushing – Wire cut EDM – Applications.

UNIT IV Chemical and Electro-chemical EnergyBased Processes (12)

Chemical machining and Electro-Chemical machining (CHMand ECM) - Etchantsmaskant - techniques of applyingmaskants-Process Parameters – Surface finish andMRR-Applications. Principles of ECM-equipments-SurfaceRoughness and MRR Electrical circuit-Process Parameters-ECG andECH - Applications.

UNIT V Thermal Energy Based Processes (10)Laser Beam machining and drilling (LBM), plasma Arc

machining (PAM) and Electron Beam Machining (EBM). Principles– Equipment –Types - Beam control techniques – Applications.

TOTAL: 45 PERIODS

Regulation 2013UNCONVENTIONAL MACHINING PROCESSES

UNIT I INTRODUCTION (6)Unconventional machining Process – Need – classification –

Brief overview .

UNIT II Mechanical Energy Based Processes (9)Abrasive Jet Machining – Water Jet Machining – Abrasive

Water Jet Machining - Ultrasonic Machining.(AJM, WJM, AWJMand USM). Working Principles – equipment used – Processparameters – MRR- Applications.

UNIT III Electrical Energy Based Processes (9)Electric Discharge Machining (EDM)- working

Principle-equipments-Process Parameters-Surface Finish and MRR-electrode / Tool – Power and control Circuits-Tool Wear – Dielectric– Flushing – Wire cut EDM – Applications.

UNIT IV Chemical and Electro-chemical EnergyBased Processes (11)

Chemical machining and Electro-Chemical machining (CHMand ECM)-Etchants – Maskant - techniques of applying maskants- Process Parameters – Surface finish and MRR-Applications.Principles of ECM- equipments-Surface Roughness and MRRElectrical circuit-Process Parameters-ECG and ECH - Applications.

UNIT V Thermal Energy Based Processes (10)Laser Beam machining and drilling (LBM), plasma Arc

machining (PAM) and Electron Beam Machining (EBM). Principles– Equipment –Types - Beam control techniques – Applications.

TOTAL: 45 PERIODS

CONTENTS

UNIT I

Introduction

1.1 Introduction .......................................................... 1.1

1.1.1 Manufacturing ............................................... 1.1

Manufacturing Engineering .......................... 1.2

1.1.2 Manufacturing operations ............................ 1.2

1. Processing operations ................................ 1.2

2. Machining operations / MaterialRemoval process ............................................. 1.2

1.1.3 Types of machining processes...................... 1.3

1.2 Conventional Machining Process .................... 1.3

1.2.1 Major Characteristics of Conventionalmachining ................................................................ 1.4

1.2.2 Drawbacks of Conventional machining...... 1.4

1.3 Unconventional Machining Process................ 1.5

1.3.1 Need for Unconventional Machining.......... 1.6

1.3.2 Characteristics of Unconventional machining 1.6

1.3.4 Classification of Unconventional machiningprocesses ................................................................... 1.7

1.4 Mechanical Energy Based Processes .............. 1.8

1.5 Thermal Energy Based Processes.................... 1.9

1.6 Electrical Energy Based Processes ................. 1.9

1.7 Chemical Energy Based Processes .................. 1.10

1.8 Hybrid Processes.................................................. 1.10

1.9 Process Selection ................................................. 1.11

Contents 1

(a) Physical parameters of the process 1.11

(b) Capability to machine - different shapes 1.12

(c) Applicability of process to different workpiece material ................................................. 1.12

(d) Process capabilities or machiningcharacteristics ................................................. 1.13

(e) Process economy........................................ 1.14

1.9.1 Advantages of Unconventional machining. 1.15

1.9.2 Disadvantages of Unconventional machining 1.15

1.9.3 Comparison of conventional machiningwith unconventional machining............................ 1.16

1.10 Points To Remember......................................... 1.16

1.11 Review Questions With Answer...................... 1.17

UNIT II

MECHANICAL ENERGY BASED PROCESSES

2.1 Introduction .......................................................... 2.2

2.2 Abrasive Jet Machining (AJM) Or MicroBlast Machining ......................................................... 2.2

2.2.1 Elements of Abrasive jet machining........... 2.4

1. Gas propulsion system.............................. 2.4

2. Abrasive feeder / Hopper......................... 2.4

3. Nozzle.......................................................... 2.5

4. Abrasives..................................................... 2.6

5. Mixing Chamber........................................ 2.7

6. Machining Chamber.................................. 2.7

2.2.2 Working Principle ......................................... 2.8

2.2.3 Process Parameters ....................................... 2.8

2 Unconventional Machining Processes

1. Standoff distance (SOD) or Nozzle tipdistance............................................................ 2.9

2. Abrasive flow rate / Mass flow rate ..... 2.9

3. Gas pressure / Nozzle pressure .............. 2.10

4. Mixing ratio ............................................... 2.10

5. Velocity of Abrasive particles................... 2.11

6. Abrasive grain size.................................... 2.11

2.2.4 Process capabilities ....................................... 2.12

2.2.5 Advantages ..................................................... 2.12

2.2.6 Disadvantages................................................ 2.13

2.2.7 Applications.................................................... 2.13

2.3 Abrasive Water Jet Machining (AWJM)........ 2.14

2.3.1 Elements of Abrasive Water jet machining 2.16

1. Pumping unit............................................. 2.16

2. Abrasive feed system................................. 2.16

3. Abrasive water jet nozzle ......................... 2.16

(i) Single side feed jet nozzle ....................... 2.17

(ii) Multi jet central feed nozzle .................. 2.18

4. Catcher........................................................ 2.18

2.3.2 Working principle.......................................... 2.18

2.3.3 Process parameters........................................ 2.18

1. Pressure of the water................................ 2.19

2. Mass flow rate of water ........................... 2.20

3. Size of the abrasive particles .................. 2.20

4. Abrasive flow rate ..................................... 2.20

5. Standoff distance....................................... 2.21

Contents 3

6. Type of abrasive material ........................ 2.21


2.3.5 Applications.................................................... 2.22

2.3.6 Advantages ..................................................... 2.22

2.3.7 Disadvantages................................................ 2.22

2.4 Water Jet Cutting Or Water Jet Machining 2.22

2.4.1 Elements of Water jet machining ............... 2.23

1. Pumping unit............................................. 2.23

2. Intensifier.................................................... 2.23

3. Accumulator ............................................... 2.24

4. Nozzle.......................................................... 2.24

5. Catcher / Drainer..................................... 2.25




2.4.5 Advantages ..................................................... 2.27

2.4.6 Disadvantages................................................ 2.28

2.4.7 Applications.................................................... 2.28

2.5 Ultrasonic Machining......................................... 2.28

2.5.1 Elements of Ultrasonic machining ............. 2.29

1. Power supply.............................................. 2.29

2. Transducer.................................................. 2.31

(i) Piezoelectric type ....................................... 2.31

(ii) Magneto restrictive transducer............... 2.31

3. Tool feed mechanism ................................ 2.32

Tool holder or Horn or Concentrator.......... 2.32


(i) Amplifying type ......................................... 2.33

(ii) Non amplifying type ............................... 2.33

4. Abrasive slurry .......................................... 2.34

Characteristics of Abrasive slurry................ 2.35

Abrasives ......................................................... 2.35



2.5.4 Material removal rate .................................. 2.41


2.5.6 Advantages ..................................................... 2.42

Limitations ...................................................... 2.43

2.5.8 Applications of ultrasonic machining......... 2.43

2.6 Other Related Process........................................ 2.43

2.6.1 Abrasive Flow Finishing process (AFF)..... 2.44

2.6.2 Magnetic Abrasive Finishing: (MAF) ......... 2.44

2.7 Points To Remember........................................... 2.44

2.8 Review Questions With Answer ...................... 2.47

UNIT III

ELECTRICAL ENERGY BASED PROCESSES

3.1 Introduction .......................................................... 3.1

3.2 Electrical Discharge Machining...................... 3.2

3.2.1 How sparking takes place............................ 3.3

3.2.2 Elements of EDM machine.......................... 3.4

1. Power supply.............................................. 3.4

Power generating circuits or generators...... 3.6

Contents 5

(i) Resistance – Capacitance type (RC type)Relaxation generator: ..................................... 3.6

(ii) Rotary impulse type generator............... 3.7

(iii) Electronic pulse generator ..................... 3.8

2. Dielectric medium / fluid........................ 3.9

The flushing process during spark erosion 3.10

Open flushing ................................................. 3.11

Pressure flushing............................................ 3.12

Suction flushing ............................................. 3.13

Combined flushing ......................................... 3.14

Problems due to Ineffective Flushing .......... 3.15

3. Tool and Tool Materials .......................... 3.15

4. Servo mechanism....................................... 3.18



1. Spark On-time (pulse time or Ton):........ 3.21

2. Spark Off-time (pause time or Toff ): ..... 3.21

3. Arc gap (or) spark gap: ........................... 3.22

4. Discharge current (current Ip):................ 3.22

5. Voltage (V): ................................................ 3.22

6. Duty cycle (): ............................................ 3.22

3.2.5 Material Removal Rate ................................ 3.22

3.2.6 Process capabilities of EDM........................ 3.23

3.2.7 Advantage....................................................... 3.24

3.2.8 Disadvantages................................................ 3.24

3.2.9 Application of EDM...................................... 3.24


3.3 Wire Electrical Discharge Machining(W-EDM) ........................................................................ 3.25

3.3.1 Elements of W- EDM: .................................. 3.26

1. Computerized Numerical Control (CNC) 3.26

2. Power Supply............................................. 3.27

3. Mechanical Section.................................... 3.27

4. Dielectric System ....................................... 3.27



1. Frequency.................................................... 3.29

2. Wire positioning......................................... 3.30

3. Wire Tension .............................................. 3.30

4. Electrode Wire Material ........................... 3.30

5. Work piece Material.................................. 3.31

6. Dielectric fluid ........................................... 3.31

7. Flushing Pressure...................................... 3.32


3.3.5 Advantages ..................................................... 3.33

3.3.6 Disadvantages................................................ 3.33

3.3.7 Applications.................................................... 3.33

3.3.8 Difference between EDM and Wire EDM.. 3.34

3.4 Other Related Process........................................ 3.34

3.4.1 Electrical Discharge Grinding (EDG)......... 3.34

3.4.2 Electric Discharge Diamond Grinding(EDDG)..................................................................... 3.35


3.6 Review Questions ................................................. 3.37

Contents 7

UNIT IV

CHEMICAL AND ELECTRO-CHEMICAL ENERGYBASED PROCESSES

4.1 Chemical Machining........................................... 4.1

4.1.1 Steps involved in chemical machining ...... 4.2

1. Cleaning the Work piece .......................... 4.2

2. Coating with masking material .............. 4.3

3. Scribing of the maskant........................... 4.3

4. Etching of required portion ..................... 4.4

5. Cleaning masking material...................... 4.4

Maskant........................................................... 4.5

4.1.2 Methods of applying the maskants ............ 4.6

Etchants........................................................... 4.6


4.1.4 Advantages of chemical machining ............ 4.8

4.1.5 Disadvantages of chemical machining ....... 4.8

4.1.6 Applications.................................................... 4.9

4.2 Electro Chemical Machining............................ 4.9

4.2.1 Electrolysis ..................................................... 4.10

Faraday’s law of electrolysis ........................ 4.11

Functions of Electrolysis ............................... 4.11

4.2.2 Elements of Electro chemical machining... 4.12

1. Power supply.............................................. 4.13

2. Electrolyte supply and filtering system .. 4.13

Electrolyte: ....................................................... 4.14

3. Tool and Tool feed system....................... 4.14


4. Workpiece and work handling system.... 4.15



4.2.5 Metal Removal Rate ..................................... 4.17


4.2.7 Advantages ..................................................... 4.18

4.2.8 Disadvantages................................................ 4.18

4.2.9 Comparison of EDM and ECM .................. 4.19

4.3 Electro Chemical Honing (ECH) ..................... 4.19

4.3.1 Elements of Electro Chemical Honing ....... 4.20



4.3.4 Advantages of ECH ...................................... 4.25

4.4 Electro Chemical Grinding (ECG) .................. 4.25

4.4.1 Elements of Electro chemical Grinding ..... 4.27

4.4.2 Metal Removal Rate in ECG ...................... 4.28


1. Contact Pressure........................................ 4.29

2. Grinding Wheel Speed.............................. 4.29

3. D.C Potential ............................................. 4.30

4. Abrasive grain size.................................... 4.30


4.4.5 Advantages ..................................................... 4.30

4.4.6 Disadvantages................................................ 4.31

4.4.7 Applications.................................................... 4.31

4.5 Other Related Processes .................................... 4.32

Contents 9

4.5.1 Electro Stream Drilling (ESD).................... 4.32

4.5.2 Electro Chemical Deburring (ECD) ............ 4.33

4.6. Points To Remember.......................................... 4.33


UNIT V

THERMAL BASED ENERGY PROCESS

5.1 Laser Beam Machining (LBM) ........................ 5.1

5.1.1 Lasing Process ............................................... 5.2

(i) Spontaneous Emission.............................. 5.3

(ii) Stimulated Emission ............................... 5.4

5.1.2 Types of laser ................................................ 5.4

(i) Based on lasing medium......................... 5.4

5.1.3 Process principle............................................ 5.6

5.14 Process parameters......................................... 5.8

5.1.5 Process Capabilities ...................................... 5.8

5.1.6 Applications of Laser Beam Machining..... 5.8

5.1.7 Laser Beam Drilling..................................... 5.9

5.1.8 Advantages ..................................................... 5.9

5.1.9 Disadvantages................................................ 5.10

5.1.10 Applications.................................................. 5.10

5.2 Electron Beam Machining ................................ 5.10

5.2.1 Elements of Electron Beam Machining...... 5.11

1. Electron Beam Gun .................................. 5.11

2. Vacuum system.......................................... 5.12

3. Power supply.............................................. 5.13


5.2.2 Working principle ........................................ 5.14


1. Beam Current ............................................ 5.15

2. Duration of pulses..................................... 5.15

3. Number of pulses required ...................... 5.16

4. Lens current ............................................... 5.16


5.2.5 Advantages ..................................................... 5.16

5.2.6 Disadvantages................................................ 5.17

5.3 Plasma Arc Machining (PAM) / Plasma ArcCutting (PAC).............................................................. 5.17

5.3.1 Plasma............................................................ 5.18

5.3.2 Types of plasma arc production ................. 5.19

(i) Non transferred type ................................ 5.20

(ii) Transferred type:...................................... 5.20

5.3.3 Elements of Plasma Arc cutting: ................ 5.20

1. Power supply system:................................ 5.21

2. Gas supply system..................................... 5.21

(i) Air plasma................................................. 5.21

(ii) Nitrogen plasma ...................................... 5.22

(iii) Argon / hydrogen plasma .................... 5.22

(iv) Oxygen plasma ........................................ 5.22

3. Cooling water system................................ 5.22

4. Plasma Torch............................................. 5.22

(i) Air Plasma Torch..................................... 5.23

(ii) Dual gas Torch........................................ 5.24

Contents 11

(iii) Water injected torch ............................... 5.25

(iv) Oxygen injected torch ............................. 5.25



Cutting Speed ................................................. 5.27

Cutting current ............................................... 5.27

Cutting height / Stand off distance (SOD) 5.27

Gas pressure and Gas flow rate.................. 5.27


5.3.7 Advantages ..................................................... 5.28

5.3.8 Disadvantages................................................ 5.28

5.3.9 Applications.................................................... 5.28



Anna University Solve Question Papers


UNIT I

Introduction

Regulation 2008

Unconventional machining Process – Need –Classification – Brief overview

Regulation 2013

Unconventional machining Process – Need –Classification – Brief overview

1.1 INTRODUCTION

1.1.1 Manufacturing

Manufacturing is the broad term used todescribe the production of components whichstarts with idea creation and ends with productrelease.

Manufacturing can be defined in two aspects.First one is a technical based definition andanother one is an economical based definition.

Technically, manufacturing can be defined asthe application of physical and chemicalprocesses to alter the shape, size and propertiesof the given material to make parts andproducts.

Economically, it is defined as the process ofdoing the value added activities in order toconvert the raw materials in to items of greatervalues by means of one or more processing and/ or assembly operations.

Introduction 1.1

Manufacturing Engineering Manufacturing engineering is the subject, which

deals with the study of various processesrequired to produce components and variousassembly operations required to assemble themin to machine and mechanisms.

1.1.2 Manufacturing operationsThese can be divided into two basic types

1. Processing operations

2. Machining operations

1. Processing operations

The processing operations can be classified as

1. Shaping processes

(a) Solidification processes

(b) Particulate processes

(c) Deformation processes

(d) Material removal processes

2. Property changing processes

(a) Heat treatment

3. Surface processing operations

(a) Coating and deposition processes

(b) Cleaning and surface treatment processes

2. Machining operations / Material Removal process Machining is an important process by which

the products are manufactured to therequired dimensions with desired surface

1.2 Unconventional Machining Processes

finish, by gradually removing the unwantedmaterial.

Removal of material is accomplished bystraining a local region of the work piece tofracture by the relative motion of the tooland the work.

1.1.3 Types of machining processes

It covers several processes which we usuallydivide into the following categories.

1. Conventional machining process

(i) Cutting – generally involves single point ormulti point cutting tools with clearlydefined geometry.

(ii) Abrasive processes such as grinding,honing.

2. Unconventional machining

Utilizing mechanical, electrical, chemical, thermalenergies in their direct form to remove the material.

1.2 CONVENTIONAL MACHINING PROCESS

In Conventional machining process the cuttingtool is used to remove the material from thework piece in the form of chips.

To perform the operation, relative motion isrequired between the tool and work.

Relative motion is given in most of themachining operations as primary motion andsecondary motion.

Primary motion is named as cutting speed andsecondary motion is named feed.

Introduction 1.3

The shape of the tool and its penetration in tothe work surface, combined with these motions,produce the desired shape of the resulting worksurface.

Examples:

Cutting processes – Shaping, turning, milling, drilling,sawing, broaching

Abrasive processes – Grinding, honing

1.2.1 Major Characteristics of Conventionalmachining

Generally macroscopic chip formed due to sheardeformation

Material removal takes place due to applicationof cutting forces.

Energy domain can be mainly mechanical

Cutting tool is harder than work piece at roomtemperature as well as under machiningcondition.

Mechanism of Material removal is shearing.

1.2.2 Drawbacks of Conventional machining

Cutting tool should be harder than the workmaterial.

Removal of chips from the work zone will be theproblem

Advanced materials like, titanium, FRC,Mnemonics, HSTR, are difficult or impossible tomachine.


1.3 UNCONVENTIONAL MACHINING PROCESS

The recently developed materials for aerospaceand nuclear industries have good mechanicalproperties such as high strength, hardness,toughness. Conventional machining processes tomanufacture the components out of thesematerials are lacking.

Innovative geometric design of products andcomponents were putting lot of pressure oncapabilities of conventional machining processes.

In the given Fig. 1.1 Merchant displayed thegradual increase in strength of the material withyear wise development of material in the aeroindustry.

These things demand the need of new processesin the industry as an efficient and economicalternative to conventional machining processes.

350

700

1400

3500

7000

14000

19301915 1945 1960 1980

Al

A lA lloy

H S T RAlloy

C om positeM aterials

Titan ium

Year of D eve lopm en t

Ulti

mat

e T

ensi

le S

tren

gth

Kg

f/cm

2

Fig. 1.1 Evolution of materials

Introduction 1.5

These processes do not necessarily usemechanical energy to provide material removal.They use other forms of energy also.

1.3.1 Need for Unconventional Machining

The need arises to machine newly developedmetals and non metals which often have specialproperties such as high strength, high hardness,high toughness that make them difficult tomachine by ordinary conventional methods.

Lack of tool materials to machine the newlydeveloped high strength materials.

The need for unusual and complex partgeometries in the aero space, automobile, marineindustries and, electronic industries.

The need to avoid surface damages.

1.3.2 Characteristics of Unconventional machining

Material removal may occur with chip formationor even no chip formation.

Chips are of microscopic size (AJM) or atomicrange (ECM)

There may be the physical tool (ECM) but nodirect contact with work.

In some processes physical tool may not bepresent (LAM)

Tool need not to be harder than work piecematerial (In case of EDM, copper is used tomachine hardened steel).


1.3.4 Classification of Unconventional machining processes

The unconventional machining processes areclassified on the basis of

Types of energy used

Mechanism of material removal

Media for energy transfer

Source of energy.

The following Fig. 1.2 shows the board classificationof the processes based on type of energy used.

Fig. 1.2 Classification based on type of energy

UnconventionalMachiningProcesses

Therm alEnergy Based

Processes

ElectricalEnergy Based

Processes

ChemicalEnergy Based

Processes

MechanicalEnergy Based

Processes

Introduction 1.7

Based on the medium of energy transfer

Electrons - EBM

Pressurized gas - AJM

Water - WJM

Ultrasonic waves - USM

Plasma, Laser – PAM, LBM

Chemical Reagent – CHM, ECM

Based on the mechanism of material removal

Erosion – Mechanical Energy basedprocesses

Electric Discharge – Electrical Energy basedprocesses

Chemical Etching – Chemical Energy basedprocesses

Melting and Vaporization – Thermal basedprocesses

Ion Displacement - Thermal based processes

During the last few decades more than 15 differentunconventional machining processes have been inventedand used for various purposes.

Some of the processes available are listed below

1.4 MECHANICAL ENERGY BASED PROCESSES

In mechanical energy based techniques, mechanicalenergy in its direct form is used to remove the materials.The mechanism of material removal is mainly erosion,chipping, not shearing as in the case of conventionalmachining.


The following are the some of the mechanical energybased processes.

(a) Ultrasonic Machining (USM)

(b) Abrasive Jet Machining (AJM)

(c) Water Jet Machining / Water Jet Cutting (WJM)

(d) Abrasive Water Jet Machining (AWJM)

(e) Abrasive Flow Machining (AFM)

(f) Magnetic Abrasive Finishing (MAF)

1.5 THERMAL ENERGY BASED PROCESSESIn thermal energy based processes the heat energy

of laser beam, electron beam, and plasma beam can beutilized directly to remove the materials from the worksurface. The mechanism of material removal is meltingand vaporization.

The following are the list of thermal basedunconventional machining processes.

(a) Plasma Arc Machining (PAM)

(b) Laser Beam Machining (LBM)

(c) Electron Beam Machining (EBM)

1.6 ELECTRICAL ENERGY BASED PROCESSESIn Electrical energy based technique the heat

energy available in the electric spark is used to removethe material from the workpiece. When a spark isdeveloped between two electrical contacts a small amountof material is removed from each contact. The mechanismof material removal is melting and vaporization ofmaterial.

Introduction 1.9

The following are the examples for electrical energybased nontraditional machining.

(a) Electrical discharge machining (EDM)

(b) Wire cut electrical discharge machining(W-EDM)

(c) Electrical Discharge Grinding (EDG)

1.7 CHEMICAL ENERGY BASED PROCESSES

In Chemical energy based techniques the materialis removed by the controlled chemical dissolution incontact with a strong acidic or alkaline chemical reagent.The mechanism of material removal process is chemicaldissolution.

The following are the examples for chemical basedenergy processes.

(a) Chemical Machining (CHM)

(b) Electro Chemical Machining (ECM)

1.8 HYBRID PROCESSES

Hybrid processes combines the advantages of bothconventional processes and nontraditional processes.

The following are the examples of different hybridprocesses.

(a) Electro Chemical Grinding (ECG)

(b) Electro Chemical Spark Machining (ECSM)

(c) Electro Chemical Arc Machining (ECAM)

(d) Electro Discharge Abrasive Grinding (EDAG)

(e) Electro Chemical Honing (ECH)


1.9 PROCESS SELECTIONThe unconventional machining processes are not

considered as substitute for conventional machiningmethods because of their very low material removal rateand high cost of machining.

The following factors are considered for the selectionof a particular unconventional process of machining.

(a) Physical parameters of the process. Example :Type and amount of power required

(b) Capability to machine different shapes

(c) Applicability of process to different work piecematerial

(d) Process capabilities or machining characteristics

(e) Process economy.

(a) Physical parameters of the processTable 1. Process parameters of the process

Paramete

rsUSM AJM ECM CHM EDM EBM LBM PAM

Potential

(V)220 220 10 – 45 150000 4500 100

Current

(Amp)12 (A.C) 1.0

10000

(D.C)–

50

(Pulsed

D.C)

0.001

(Pulsed

D.C.)

2

(Average

200

Peak)

500

(D.C)

Power

(W)2400 220 100000 – 2700 150 – 50000

Cap

(m.m)0.25 0.75 0.20 – 0.025 100 150 7.6

MediumAbrasive

in water

Abrasive

in gas

Electrolyte Liquid

chemical

Liquid

dielectricVaccum Air

Argon

or

hydrogen

Introduction 1.11

(b) Capability to machine - different shapes

Application of unconventional machining process isalso influenced by geometric shapes it has to machine.

Very small holes (Dia < 0.125mm)(Smaller than dia range ofconventional drill bit)

– EBM, LBM

Holes with large depth to diaratio (d/D > 20) – ECM, EDM

Holes that are not round – EDM, ECM

Narrow slots – EBM, LBM,WJC, AWJC,W-EDM

Shallow pockets and surfacedetails on flat surfaces. – CHM

(c) Applicability of process to different work piecematerial

All the hard and difficult to machine materials canbe easily machined by unconventional machiningprocesses. But all the methods cannot be used to machineall the materials.

Table 2. Applicability of process

Metals Alloys

Process Aluminium SteelSuperalloy

TitaniumRefractory

material

USM Poor Fair Poor Fair Good

AJM Fair Fair Good Fair Good

ECM Fair Good Good Fair Fair

CHM Good Good Fair Fair Poor


Metals Alloys

Process Aluminium SteelSuperalloy

TitaniumRefractory

material

EDM Fair Good Good Good Good

EBM Fair Fair Fair Fair Good

LBM Fair Fair Fair Fair Poor

PAM Good Good Good Fiar Poor

Non-Metals

Process Ceramics Plastic Glass

USM Good Fair Good

AJM Good Fair Good

ECM – – –

CHM Poor Poor Fair

EDM – – –

EBM Good Fair Fair

LBM Good Fair Fair

PAM – Poor –

(d) Process capabilities or machining characteristics

The machining characteristics of differentnon-conventional processes can be analyzed with respectto

(a) Metal removal rate

(b) Tolerance maintained

(c) Surface finish obtained

(d) Depth of surface damage

(e) Power required for machining

Introduction 1.13

The process capabilities of non-conventionalmanufacturing processes have been compared in table

Table 3. Process capabilities

Process MRR

mm3/min

Tolerance(p)

Surface(p) CLA

Depth ofsurfacedamage

(p)

Power(watts)

USM 300 7.5 0.2-0.5 25 2400

AJM 0.8 50 0.51.2 2.5 250

ECM 15000 50 0.1-2.5 5.0 100000

CHM 15 50 0.5-2.5 50 –

EDM 800 15 0.2-1.2 125 2700

EBM 1.6 25 0.5-2.5 250 150(average)

2000(peak)

LBM 0.1 25 0.5-1.2 125 2(average)

PAM 75000 125 Rough 500 5000

Conventinoal

machining

5000 50 0.5-5.0 25 3000

(e) Process economy

The economics of the various processes are analysedon the basis of following factors and given in Table

(a) Capital cost

(b) Tooling cost

(c) Consumed power cost

(d) Metal removal rate efficiency

(e) Tool wear.


Table 4. Process economy

Process Capitalcost

Tooling cost

Powerconsumption

cost

Materialremoval rate

efficiency

Toolwear

USM. L L H M

AJM VL L L H L

ECM VH M M L VL

CHM M L H M VL

EDM M H L H H

EBM H L L VH VL

LBM L L VL VH VL

PAM VL L VL VL VL

MCG L L L VL L

1.9.1 Advantages of Unconventional machining They are suitable for machining hard, brittle

and the so called ‘Exotic’ materials.

They are suitable for workpieces with highshape complexity.

They fulfill high surface integrity and precisionrequirements.

They meet miniaturization requirements.

1.9.2 Disadvantages of Unconventional machining Very slow material removal rate.

Initial cost is very high.

Most of the processes are not suitable for massproduction.

Introduction 1.15

1.9.3 Comparison of conventional machining withunconventional machining

Table 5. Comparison between conventional andunconventional machining

S.NoConventional

MachiningUnconventional

machining

01 There is a physicalcontact between hardtool and work material

No Such physicalcontact

02 Tool should be harderthan work material

No tool (LBM), If tool isused, no need to beharder than workmaterial (USM, EDM)

03 Mechanism of materialremoval is shearing

Mechanism of materialremoval will vary basedon energy used

04 Chip formation will bein the macroscopic level

Chips formed are in therange of microscopiclevel (AJM), atomiclevel (ECM)

05 Materials like titanium,FRC, HSTR, Ceramicsare difficult to machine

These materials areeasily machined.

1.10 POINTS TO REMEMBER

Unconventional machining process are classified onthe basis of

Type of energy used.

Mechanism of material removal.

Media for energy transfer.


Source of energy.

Based on energy used the processes are classified as

Mechanical energy based processeseg:- WJM, AJM, USM

Thermal energy based processeg:- EBM, PAM, LBM

Electrical energy based processeg:- EDM, EDG, W-EDM

Chemical energy based processeg:- CHM, ECM, ECG, ECH

Process selection can be done on the basis of

Physical parameters of the process.

Capability to m/c different components.

Process capabilities.

Process economy.

Suitability for different workpiece materials.

1.11 REVIEW QUESTIONS WITH ANSWER

1. State the need of unconventional machiningprocesses.

The need arises to machine newly developedmetals and non metals which often have specialproperties such as high strength, high hardness,high toughness that make them difficult tomachine by ordinary conventional methods.

Lack of tool materials to machine the newlydeveloped high strength materials.

Introduction 1.17

2. Write the importance of surface finishing in themachining operations. [May/ June 2014]

Surface finish is more important in machiningcomponents, because it reduces the friction whenthe component makes contact with the other.And also it gives the good appearance. Generallyin aerospace and medical applications goodsurface finish is required.

3. What is the necessity of unconventional or non– traditional machining processes?

[May/ June 2012]

Refer Answer for Question No 1

4. Mention the thermal energy basedUnconventional Machining Processes.

[ May/ June 2012]

The following are the list of thermal basedunconventional machining processes.

(a) Plasma Arc Machining (PAM)

(b) Laser Beam Machining (LBM)

(c) Electron Beam Machining (EBM)

5. What are the advantages of UnconventionalMachining Processes? [May/June 2013]

They are suitable for machining hard, brittleand the so called ‘Exotic’ materials.

They are suitable for work pieces with highshape complexity.

They fulfill high surface integrity andprecision requirements.

They meet miniaturization requirements.


6. List the Unconventional Machining processesbased on thermal energy


7. Name the important factors that should beconsidered during the selection of anunconventional machining process for a givenjob. [May/ June 2011]

The following factors are considered for the selectionof a particular unconventional process of machining.

(a) Physical parameters of the process. Example :Type and amount of power required

(b) Capability to machine- different shapes

(c) Applicability of process to different work piecematerials. (d) Process capabilities or machiningcharacteristics (e) Process economy.

8. Classify modern machining processes on thebasis of the type of energy employed.

[May/ June 2011]

Modern Machining processes are classified asfollows based on type of energy employed.

Mechanical Energy based processes

Electrical Energy based processes

Chemical Energy based processes

Thermal Energy based processes.

Introduction 1.19

9. Enlist the requirement that demands the use ofadvanced machining process.

[Nov/Dec 2012, April/May 2008]


10. Why unconventional mechanical machiningprocess is not so effective on soft metals Likealuminum? [Nov/Dec 2012, April/May 2008]

Unconventional Machining process is not veryeffective on soft metals like aluminium because it ishighly difficult to maintain the close tolerance andaccuracy desired.

UnconventionalMachiningProcesses

Therm alEnergy Based

Processes

ElectricalEnergy Based

Processes

ChemicalEnergy Based

Processes

MechanicalEnergy Based

Processes


11. What are the industrial needs forunconventional machining processes?

[May/June 2009]


12. Write down the energy transfer media, energysource and mechanism of metal removal for thefollowing process.

(a) Water jet machining Electro chemicalmachining

ProcessEnergy

TransferMedia

Energysource

Mechanismof Material

removal

Water jetmachining

Water Mechanical Erosion

Electro chemicalmachining

Electrolyte Chemicalreaction

Dissolution

13. Why is unconventional mechanical machiningprocess not popular? [Nov/Dec 2009]

The unconventional machining process is not sopopular because of its cost and not able to go for massproduction.

14. How do you minimize pulsation in Water jetmachining? [Nov/Dec 2009]

In water jet machining the pulsation is reduced byusing an Accumulator which stores the water andsupplies continuously.

Introduction 1.21

15. Compare Unconventional and conventionalmachining processes

S.No.

ConventionalMachining

Unconventionalmachining

01 There is a physicalcontact between hardtool and work material

No Such physical contact

02 Tool should be harderthan work material

No tool (LBM), If tool isused, no need to beharder than workmaterial (USM, EDM)

03 Mechanism of materialremoval is shearing

Mechanism of materialremoval will vary basedon energy used

04 Chip formation will be inthe macroscopic level

Chips formed are in therange of microscopiclevel (AJM), atomic level(ECM)

05 Materials like titanium,FRC, HSTR, Ceramicsare difficult to machine

These materials areeasily machined.

16. Recommend the suitable process to cut glassinto two pieces.

Glass

For non conductive materials certain process likeECM, EDM, PAM, EBM are ruled out, because they aresuitable to m/c only electrically conductive materials.

LBM is avoided b’cas it is an expensive process.

WJM, AWJM, USM can be applied. Based onaccuracy required any one can be selected.


Documents

AIR WALK PUBLICATIONS - airwalkbooks.comairwalkbooks.com/images/pdf/pdf_46_1.pdf · Electric Discharge Machining (EDM)- working Principle-equipments-Process Parameters-Surface