105877716 Nontraditional Machining

7/27/2019 105877716 Nontraditional Machining

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NONTRADITIONAL (OR)

UNCONVENTIONAL MACHINING


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History of Manufacturing

Manufacturing started during 5000 4000 BC

Wood work,ceramics,stone and metal work

Steel Production 600-800 AD

Industrial Revolution 1750 AD: Machine tools run byinvention of steam engine

Mass Production and Interchangeable Parts

Computer Controlled Machines 1965

CNC,FMS systems


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Historical development of materials

- The Early Days

Period Metals and Casting Forming Process

Egypt ~3100 B.C. to ~300 B.C

Greece ~1100 B.C. to~146 B.C

Roman Empire ~500B.C. to 476 A.D

Middle Ages 476 to1492

Renaissance 14th to

16th centuries

Before 4000B.C

Gold,copper and meteoriticiron

Hammering

4000-3000B.C.

Copper casting,stone andmetal molds,lost waxprocess,silver,lead,tin,bronze

Stamping Jewelry

3000-2000B.C.

Bronze casting Wire by cuttingand drawing, gold

leaf

2000-1000B.C.

Wrought iron,brass

1000-1 B.C. Cast iron, cast steel Stamping of coins

1A.D 1000A.D

Zinc steel Armor,coinage,for ging steel swords

1000-1500A.D.

Blast furnace, typemetals,casting ofbells,pewter

Wire drawing,goldsilver smith work


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Industrial Revolution

1750-1850

1500-1600 A.D. Cast iron cannon, tinplate Water power for metal

working,rolling mill forcoinage

1600-1700 A.D. Permanent mold casting,brassfrom copper and metallic zinc

Rolling(lead,gold,silver)

Shape rolling(lead)

1700-1800 A.D. Malleable cast iron,cruciblesteel

Extrusion (lead pipe),deep drawing,rolling(iron bars androds)

1800-1900 A.D. Centrifugal casting,Bessemer

process,electrolyticaluminum,nickel steels,Babbitt,galvanized steel, powdermetallurgy, tungsten steel, openhearth steel

Steam hammer, steel

rolling,seamless tubepiercing,steel railrolling, continuousrolling , electroplating


- The Industrial Revolution


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WW I and WW II 1900-1920A.D.

Tube rolling, hotextrusion

1920-1940A.D.

Die casting Tungsten wire frompowder

1940-1950A.D.

Lost wax for engineeringparts

Extrusion(steel),swaging, powdermetal for engineeringparts

Space Age 1950-1960A.D.

Ceramic mold, nodulariron,semiconductors,continuous casting

Cold extrusion(steel),explosiveforming,thermomechanical treatment

1960-1970 A.D Squeeze casting, singlecrystal turbine blades

Hydrostaticextrusion,electroforming

1970-1980 s Compactedgraphite,vacuumcasting,organically bondedsand,automation ofmolding and pouring, largealuminum castings foraircraft structures rapid

solidification technology

Precisionforging,isothermalforging, super plasticforming,die design byanalytical methods, netshape forming


- The Modern Age


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Requirements of a good manufacturing system

Product should meet design requirement

Economical Process

Quality should be built into the system

Should be flexible and responsive to new technology High productivity: Best utilization of man, material,

machine, capital and available resources.


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Steps in Modern Manufacturing

Production drawings;

Instruction manuals

Conceptual design and

evaluation Feasibility study

Designanalysis;codes/standards

review; physical and

analytical models

Prototype production

testing and evaluation

Definition of product need,

marketing information

Material Specification;process

and equipment selection;

safety review

Pilot Production

Production

Inspection and quality

assurance

Packaging; marketing and

sales literature

Product

CAD

CAM and CAPP


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Manufacturing of a Paper Clip

What is the function

How long does it last

How critical is the part

Material Metallic - what type

Non metallic plastic Dimension Diameter of clip

Shape of clip

Method of manufacturing Manual

Automated

Function based design Stress, StrainLife of clip

Stiffness

Style Appearance,Color,Finish

Plating,painting


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AISI 1010,swaged

and cadmium plated

AISI 1020,forging

and chromium plated

AISI 1010, luster finished

coil stock,profile

milled,resistance welded

and chromium plated

formed,welded and plated

AISI 1008, press

formed,welded and plated

Cold drawn medium

carbon steel,( similar to

AISI 1035) bright zincplated

Headed brass,nickel plated

Aluminum permanent mold

casting,machined , polished

and buffed Hardened high-carbonsteel,thread rolled and

chromium plated

AISI 1010,stamped andchromium plated

Case hardened forgingquality steel parts, black

oxide coating

AISI 1040

forging,carburized and

chromium plated

AISI 1010,stamped and

coined and chromium

plated

AISI 1010, stamped and

chromium plated

Aluminum alloy forging,

polished and buffedForged aluminum

tubing(alloy similar to

6063), polished and buffed

AISI 1010 welded tubing,

assembly resistance welded

and electrostatically

painted

AISI 1008,press formed

resistance welded and

painted

AISI 1020 tubing, machine

threaded and painted

Seamless AISI 1020 tubing

swaged tube sectionsbrazed into fork

crown,painted

Manufacturing

of a bicycle


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The requirements that lead to the development of

nontraditional machining.

Very high hardness and strength of the material. (above

400 HB.)

The work piece is too flexible or slender to support the

cutting or grinding forces.

The shape of the part is complex, such as internal and

external profiles, or small diameter holes.

Surface finish or tolerance better than those obtainable

conventional process. Temperature rise or residual stress in the work piece are

undesirable.


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NONTRADITIONAL MACHINING PROCESSES1. Mechanical Energy Processes (USM, WJC, AJM)

- high velocity stream of abrasives or fluid(or both)

2. Electrochemical Processes (ECM)- reverse of electroplating

3. Thermal Processes (EDM, Wire EDM, EBM, LBM,

PAC)

- vaporizing of a small area of work surface

4. Chemical Processes (CHM, Chemical Blanking,

PCM)


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Nontraditional Processes Used

When:1. Material is either very hard, brittle or both;

or material is very ductile: difficult material

2. Part geometry is complex or geometricrequirements impossible with conventional

methods: difficult geometry

3. Need to avoid surface damage or

contamination that often accompanies


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1. Mechanical Energy Processes

Ultrasonic machining (USM)

Water jet cutting (WJC)

Abrasive jet machining (AJM)


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1a) Ultrasonic Machining (USM

& UW)

Abrasives in a slurry are driven at high velocity

against work by a vibrating tool (low amplitude &high frequency)

Tool oscillation is perpendicular to work surface

Abrasives accomplish material removal
http://www.youtube.com/watch?v=Ea0eDp0boQU&feature=relatedhttp://www.youtube.com/watch?v=Ea0eDp0boQU&feature=related


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USM Applications

Used only on hard and brittle workmaterials: ceramics, glass, carbides, and

hard metals.

Shapes include non-round holes, holes

along a curved axis

Coining operations - pattern on tool is

imparted to a flat work surface

Produces virtually stress free shapes


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Uses high pressure,high velocity stream of

water directed at work

surface for cutting

1b) Water Jet Cutting(WJC)

5-axes water jet cutting

7 axis for trimming large parts
http://www.jaylenosgarage.com/extras/tools/calypso-waterjet-cutter/http://www.youtube.com/watch?v=GCH2BSfLJ70&feature=player_embeddedhttp://www.youtube.com/watch?v=kRU0RHgS5R4&feature=relatedhttp://www.youtube.com/watch?v=iGQezjZ28N0&feature=relatedhttp://www.youtube.com/watch?v=iGQezjZ28N0&feature=relatedhttp://www.youtube.com/watch?v=kRU0RHgS5R4&feature=relatedhttp://www.youtube.com/watch?v=GCH2BSfLJ70&feature=player_embeddedhttp://www.jaylenosgarage.com/extras/tools/calypso-waterjet-cutter/


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WJC Applications

Usually automated using CNC or industrialrobots

Best used to cut narrow slits in flat stock

such as:plastic, textiles, composites, tile,

and cardboard

Not suitable for: brittle materials (e.g., glass)

When used on metals, you need to add to

the water stream: abrasive particles

Smallest kerf width about 0.4 mm for metals,


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WJC Advantages

No crushing or burning of work surface

Minimum material loss

No environmental pollution

Ease of automation


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High velocity gas stream containing

abrasive particles (aka: sand blastingor

bead blasting)

Normally used as a finishing process rather

1c) Abrasive Jet Machining (AJM)

2 Electrochemical Machining


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2. Electrochemical MachiningProcesses

Electrical energyused in combination

with chemical

reactions to removematerial

Reverse of:

electroplating Work material must

be a: conductor

Feature dimensions

Courtesy of AEG-Elotherm-Germany


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Material removal by anodic dissolution,using electrode (tool) in close proximity

to work but separated by a rapidly

flowing electrolyte

Electrochemical Machining (ECM)


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ECM Operation

Material is deplated from anode workpiece(positive pole) and transported to a cathode

tool (negative pole) in an electrolyte bath

Electrolyte flows rapidly between two poles

to carry off deplated material, so it does not:

plate onto the tool Electrode materials: Cu, brass, or stainless

steel


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ECM Applications Die sinking - irregular shapes and

contours for forging dies, plastic molds,

and other tools

Multiple hole drilling - many holes can bedrilled simultaneously with ECM

No burrs created no residual stress

Trimmer et al, APL 2003Schuster et al, Science 2000


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Material Removal Rate of ECM

Based on Faraday's First Law: rate of metaldissolved is proportional to the current

MRR = Ar = CI

whereI= current;A = frontal area of the electrode

(mm2), r = feed rate (mm/s), and = efficiency

coefficient= specific removal rate with work material;

M= atomic weight of metal (kg/mol)

= density of metal (kg/m3),

F= Faraday constant (Coulomb)

n = valency of the ion;

Fn

MC

=


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Equations for ECM (Cont)

Resistance ofElectrode:

gR rA

=

Gap, g

Area, A

ris the resistivity of the

electrolyte fluid (Ohmm)


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Example: ECM through a plate

Aluminum plate, thickness t= 12 mm; Rectangular hole to be cut:

L = 30mm, W= 10mm

Applied current: I= 1200 amps.

Efficiency of 95%,

Determine how long it will take to cut the

hole?

30mm

10mm

Ideal CAl= 3.4410-2 mm3/amps

- other C values in Table 26.1


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Solution:

Frontal Area, A = 30 10 = 300 mm2

Applying MRR = Ar = CI

At 95% efficiency,Feed rate f

r= CI/A

fr= 0.95(3.44 10-2 mm3/amps)(1200 A)/(300

mm2)

fr= 0.131 mm/s

Find machine Time:

3 Thermal Energy Processes


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3. Thermal Energy Processes -Overview

Very high temperatures, but only: locally

Material is removed by: vaporization

Problems and concerns:

Redeposition of vaporized metal

Surface damage and metallurgical damageto the new work surface

In some cases, resulting finish is so poor that


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3. Thermal Energy Processes

Electric discharge machining (EDM)

Electric discharge wire cutting (Wire EDM)

Electron beam machining (EBM)

Laser beam machining (LBM)

Plasma arc cutting or machining (PAC)


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3a) Electric Discharge Machining(EDM)

One of the most widely used nontraditionalprocesses

Shape of finished work is inverse of tool shape

Sparks occur across a small gap between tool andwork
http://www.youtube.com/watch?v=k646HE6MxE4http://www.youtube.com/watch?v=q4FinKsDfwwhttp://www.youtube.com/watch?v=q4FinKsDfwwhttp://www.youtube.com/watch?v=k646HE6MxE4


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Work Materials in EDM

Work materials must be: electricallyconducting

Hardness and strength of work material

are: not factors

Material removal rate depends primarily on:

melting point of work material

Applications:

Molds and dies for injection molding and


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EDM uses small diameter wire as electrodeto cut a narrow kerf in work similar to a:

bandsaw

3b) Wire EDM
http://www.youtube.com/watch?v=pBueWfzb7P0&feature=relatedhttp://www.youtube.com/watch?v=pBueWfzb7P0&feature=related


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Material Removal Rate of EDM Weller Equation (Empirical);

Maximum rate: RMR =

whereK= 664

(C1.23mm3/amps);I= discharge

current; Tm = melt temp of work

material

Actual material removal rate:

MRR = vf hwkerf

23.1

mT

KI

While cutting, wire is

continuously advanced

between supply spooland take up spool to:

maintain a constant

diameter


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Wire EDM Applications

Ideal for stamp and diecomponents

Since kerf is so narrow, it

is often possible tofabricate punch and die in

a single cut

Other tools and parts withintricate outline shapes,

such as lathe form tools,

extrusion dies, and flat


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Part loaded inside avacuum chamber

Beam is focused

through electromagnetic

lens, reducing diameter

to as small as 0.025 mm

Material is vaporized in

a very localized area

3c) Electron Beam Machining (EBM)


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EBM Applications

Ideal formicromachining Drilling small diameter holes down to 0.05

mm (0.002 in)

Cutting slots only about 0.025 mm (0.001

in.) wide

Drilling holes with very highdepth to diameter ratios

Ratios greater than 100:1


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Generally usedfor: drilling,

slitting, slotting,

scribing, andmarking

operations

Holes can be

made down to

0.025 mm

3d) Laser Beam Machining (LBM)

) C ( C)


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Uses plasma stream at

very high temperatures

to cut metal 10,000C to

14,000C

Plasma arc generated

between electrode in

torch and anode

workpiece

The plasma flows

through water cooled

nozzle that constricts

3e) Plasma Arc Cutting (PAC)


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Applications of PAC

Most applications of PAC involvecutting offlatmetal sheets and

plates

Hole piercing and cutting along a

defined path

Can be operated by hand held

torch or automated by CNC

Can cut any: electrically

conductivemetal


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4. Chemical Machining (CHM)

CHM Process:

Cleaning to insure uniform etching

Masking a maskant (resist, chemically resistant to

etchant) is applied to portions of work surface not to

be etched

Patterning of maskant

Etching part is immersed in etchant which chemically


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Maskant - Photographic Resist

Method Masking materials contain photosensitive

chemicals

Maskant is applied to work surface (dip coated,

spin coated, or roller coated) and exposed to light

through a negative image of areas to be etched

These areas are then removed using photographic

developing techniques

Remaining areas are vulnerable to etching

Applications:

Small arts on thin stock roduced in hi h uantities


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Material Removal Rate in CHM

Generally indicated as penetration rates, i.e.mm/min.

Penetration rate unaffected by exposed surface

area

Etching occurs downward and under the maskant

In general, d u 2d, Etch Factor: Fe=

(see Table 26.2 pg 637)

u

d


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Chemical Blanking

Uses CHM to cut verythin sheetmetal parts

down to 0.025 mm thick

and/or for intricate

cutting patterns

Conventional punch anddie does not work

because stamping forces

dama e the thin

Parts made by chemical

blanking (photo courtesy

of Buckbee-Mears St.

Paul).


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CHM Possible Part Geometry

Features Very small holes

Holes that are not round

Narrow slots in slabs and plates

Micromachining

Shallow pockets and surface details in flatparts

Special contoured shapes for mold and

die applications


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Chemical Machining (CM)

Oldest nontraditional machining process.

material is removed from a surface by chemicaldissolution using chemical reagents or etchants like

acids and alkaline solutions.

Types of chemical machining

1. chemical MillingBy selectively attacking different areas of

work piece with chemical reagents shallow cavities can

be produced on plates, sheets, forging and extrusion.

2. chemical blankingIt is similar to blanking in sheet metals except

material is removed by chemical dissolution rather than

by shearing. Used in bur free etching of printed circuit

boards, decorative panels etc.


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CHEMICAL MACHINING


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3. Photochemical blanking

This process is effective in blanking fragile work

pieces and materials. Material is removed using

photographic techniques. Applications are electric motor

lamination, flat springs, masks for color television,

printed circuit cards etc.


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ELECTROCHEMICAL MACHINING


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Electrochemical Machining

Reverse of electroplating

An electrolyte acts as a current carrier and high

electrolyte movement in the tool-work-piece gap washes

metal ions away from the work piece (anode) before they

have a chance to plate on to the tool (cathode).

Tool generally made of bronze, copper, brass or

stainless steel.

Electrolyte salt solutions like sodium chloride or sodium

nitrate mixed in water.

Power DC supply of 5-25 V.


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Advantages of ECM

Process leaves a burr free surface. Does not cause any thermal damage to the parts.

Lack of tool force prevents distortion of parts.

Capable of machining complex parts and hard materials

ECM systems are now available as Numerically

Controlled machining centers with capability for high

production, high flexibility and high tolerances.


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ELECTROCHEMICAL GRINDING


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Electrochemical Grinding (ECG)

Combines electrochemical machining with conventional

grinding.

The equipment used is similar to conventional grinder

except that the wheel is a rotating cathode with abrasive

particles. The wheel is metal bonded with diamond or Al

oxide abrasives.

Abrasives serve as insulator between wheel and work

piece. A flow of electrolyte (sodium nitrate) is provided

for electrochemical machining.

Suitable in grinding very hard materials where wheel

wear can be very high in traditional grinding.


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ELECTRICAL DISCHARGE MACHINING


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Electrical discharge machining (EDM)

Based on erosion of metals by spark discharges. EDM system consist of a tool (electrode) and work piece,

connected to a dc power supply and placed in a

dielectric fluid.

when potential difference between tool and work piece ishigh, a transient spark discharges through the fluid,

removing a small amount of metal from the work piece

surface.

This process is repeated with capacitor discharge ratesof 50-500 kHz.


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dielectric fluid mineral oils, kerosene, distilled and

deionized water etc.

role of the dielectric fluid

1. acts as a insulator until the potential is sufficiently

high.

2. acts as a flushing medium and carries away the

debris.

3. also acts as a cooling medium.

Electrodes usually made of graphite.

EDM can be used for die cavities, small diameter deep

holes,turbine blades and various intricate shapes.


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WIRE EDM


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Wire EDM

This process is similar to contour cutting with a bandsaw.

a slow moving wire travels along a prescribed path,

cutting the work piece with discharge sparks.

wire should have sufficient tensile strength and fracturetoughness.

wire is made of brass, copper or tungsten. (about

0.25mm in diameter).


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LASER BEAM MACHINING


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ELCTRON BEAM MACHINING


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Electron beam machining (EBM)

similar to LBM except laser beam is replaced by highvelocity electrons.

when electron beam strikes the work piece surface, heat

is produced and metal is vaporized.

surface finish achieved is better than LBM. Used for very accurate cutting of a wide variety of

metals.


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WATER JET MACHINING


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Water jet machining (WJT)

Water jet acts like a saw and cuts a narrow groove in thematerial.

Pressure level of the jet is about 400MPa.

Advantages

- no heat produced

- cut can be started anywhere without the need forpredrilled holes

- burr produced is minimum

- environmentally safe and friendly manufacturing.

Application used for cutting composites, plastics,fabrics, rubber, wood products etc. Also used in foodprocessing industry.


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ABRASIVE JET MACHINING


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ULTRASONIC MACHINING


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ULTRASONIC MACHINING (UM)

In UM the tip of the tool vibrates at low amplitude and athigh frequency. This vibration transmits a high velocity to

fine abrasive grains between tool and the surface of the

work piece.

material removed by erosion with abrasive particles.

The abrasive grains are usually boron carbides.

This technique is used to cut hard and brittle materials

like ceramics, carbides, glass, precious stones and

hardened steel.

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105877716 Nontraditional Machining

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