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Nontraditional Machining Nontraditional Machining

ProcessesProcesses

By

H.G.Shah



History of Material Development



The requirements that lead to the development

of nontraditional machining

• Very high hardness and strength of the material. (above 400 HB.)

• The work piee is too fle!ible or slender to s"pport the "tting orgrinding fores.

• The shape of the part is omple!# s"h as internal and e!ternal

profiles# or small diameter holes.

• $"rfae finish or tolerane better than those obtainable onventional

proess.

• Temperat"re rise or resid"al stress in the work piee are "ndesirable.



Conventional Machining VS

NonConventional Machining

• The "tting tool and workpiee are always in physial ontat# with arelative motion against eah other# whih res"lts in frition and asignifiant tool wear .

• %n non&traditional proesses# there is no physial ontat between thetool and workpiee. 'ltho"gh in some non&traditional proesses toolwear e!ists# it rarely is a signifiant problem.

• aterial removal rate of the traditional proesses is limited by the

mehanial properties of the work material. on&traditional proesseseasily deal with s"h diffi"lt&to&"t materials like eramis anderami based tool materials# fiber reinfored materials# arbides#titani"m&based alloys.



ontinue!

• %n traditional proesses# the relative motion between the tool and workpiee is typially rotary or reiproating. Th"s# the shape of the works"rfaes is limited to ir"lar or flat shapes. %n spite of widely "sed **systems# mahining of three&dimensional s"rfaes is still a diffi"lt task.ost non&traditional proesses were develop +"st to solve this problem.

• ahining of small avities# slits# blind or thro"gh holes is diffi"lt withtraditional proesses# whereas it is a simple work for some non&traditional proesses.

• Traditional proesses are well established# "se relatively simple andine!pensive mahinery and readily available "tting tools. on&traditional proesses re,"ire e!pensive e,"ipment and tooling as wellas skilled labor# whih inreases signifiantly the prod"tion ost.



lassification "# Processes

• ehanial etal removal -roesses

• %t is harateried by the fat that the material

removal is d"e to the appliation of mehanial

energy in the form of high fre,"eny vibrations or

kineti energy of an abrasive +et.

•/. ltra soni ahining ($).

1. 'brasive 2et ahining ('2).

3. ater 2et ahining (2).



ontinue!

$ %lectro&hemical$ 't is (ased on electro&chemical dissolution of materials (y an

electrolyte under the influence of an e)ternally applied electrical

potential.

*. %lectro&hemical Machining +%M,. -. %G

%D



ontinue!

$ Thermal Method

The material is removed due to controlled/ locali0ed heating

of the 1or2 piece. 't result into material removal (y melting

and evaporation.

The source of heat generation in such cases can (e 1idely

different.

*.%lectric Discharge Machining +%DM,.

-. Plasma 3rc Machining +P3M,. . %BM 4. 5BM



3(rasive 6ater&7et utting

• ' stream of fine grain abrasives mi!ed with air or s"itablearrier gas# at high press"re# is direted by means of anole on the work s"rfae to be mahined.

• The material removal is d"e to erosive ation of a high

press"re +et.

$ '2 differ from the onventional sand blasting proess inthe way that the abrasive is m"h finer and effetive ontrolover the proess parameters and "tting. sed mainly to "t

hard and brittle materials# whih are thin and sensitive toheat.



3(rasive 7et Machining Setup



Typical 37M Parameters

$ 3(rasive 8 3luminum o)ide for 3l and Brass.

8 Si for Stainless steel and eramic9

8 Bicar(onate of soda for Teflon

8 Glass (ed for polishing.$ Si0e

8 *:&*; Micron

$ <uantity

8 ;&*; liter=min for fine 1or2

8 *:&: liter=min for usual cuts.

8 ;:&*:: liter=min for rough cuts.




$ Medium 8 Dry air/ "-/ N-

8 <uantity> : liter=min

8 ?elocity> *;:&:: m=min

8 Pressure> -::&*:: @Pa

$ No00le

8 Material> Tungsten car(ide or saffire

8 Stand of distance> -.;4&A; mm 8 Diameter> :.*&*.- mm

8 "perating 3ngle> :C to vertical




$ #actors affecting M> 8 Types of a(rasive and a(rasive grain si0e

8 #lo1 rate

8 Stand off distance 8 No00le Pressure



• Advantages of AJM • 5ow apital ost.

• 5ess vibration.• 6ood for diffi"lt to reah area.

• o heat is genera7ted in work piee.

• 'bility to "t intriate holes of any hardness and brittleness in thematerial.

• 'bility to "t fragile# brittle hard and heat sensitive material witho"tdamage

• Disadvantages of AJM:

• 5ow metal removal rate.• 8"e to stay "tting a"ray is affeted.

• -arivles is imbedding in work piee.

• 'brasive powder annot be re"sed.



• Applications of AJM:

• 9or abrading and frosting glass# it is more eonomial than aid

ething and grinding.

• 9or doing hard s"ff"ses safe removal of smears and eramis

o!ides on metals.

• :esistive oating et from ports to deliate to withstand normalsrapping.

• 8eliate leaning s"h as removal of sm"dges from anti,"e

do"ments.

• ahining semiond"tors s"h as germani"m et.



ater 2et ahining

• The water +et mahining involves direting a high press"re (/;0&/000-a) high veloity (;40&/400 m<s) water +et(faster than the speed of

so"nd) to the s"rfae to be mahined. The fl"id flow rate is typially from

0.; to 1.; l<min

• The kineti energy of water +et after striking the work s"rfae is red"ed

to ero.• The b"lk of kineti energy of +et is onverted into press"re energy.

• %f the loal press"re a"sed by the water +et e!eeds the strength of the

s"rfae being mahined# the material from the s"rfae gets eroded and

a avity is th"s formed.

• The water +et energy in this proess is onentrated over a very smallarea# giving rise to high energy density(/010 w<mm2) High



6ater 7et Machining Setup



*ontin"e=

• ater is the most ommon fl"id "sed# b"t additives s"h as alohols#oil prod"ts and glyerol are added when they an be dissolved inwater to improve the fl"id harateristis.

• Typial work materials involve soft metals# paper# loth# wood# leather#r"bber# plastis# and froen food.

• %f the work material is brittle it will frat"re# if it is d"tile# it will "t well>

• The orifie is often made of sapphire and its diameter rangesfrom /.1mm to 0.; mm>



ater 2et ?,"ipments

$ 't is consists of three main units

+i, 3 pump along 1ith intensifier.

+ii,utting head comprising of no00le and 1or2 ta(le movement.

+iii, filter unit for de(ries/pout impurities.

$ 3dvantages & no heat produced

& cut can (e started any1here 1ithout the need for predrilled holes

& (urr produced is minimum

& environmentally safe and friendly manufacturing.

3pplication 8 used for cutting composites/ plastics/ fa(rics/ ru((er/ 1ood products

etc. 3lso used in food processing industry.



'brasive ater +et mahining

• The rate of "tting in water +et mahining# parti"larly while "tting

d"tile material# is ,"ite low. *"tting rate an be ahieved by mi!ing

abrasive powder in the water to be "sed for mahining.

• %n Abrasive Water Jet Cutting # a narrow# fo"sed# water +et is mi!ed with

abrasive partiles.

• This +et is sprayed with very high press"res res"lting in high veloities

that "t thro"gh all materials.

• The presene of abrasive partiles in the water +et red"es "tting

fores and enables "tting of thik and hard materials (steel plates over

@0&mm thik an be "t).

• The veloity of the stream is "p to A0 m<s# abo"t 1.; times the speed of

so"nd.



ontinue..

• 'brasive ater 2et *"tting proess was developed in /A70s to

"t materials that annot stand high temperat"res for stress

distortion or metall"rgial reasons s"h as wood and

omposites# and traditionally diffi"lt&to&"t materials# e.g.eramis# glass# stones# titani"m alloys



Eltrasonic machining

$ History

• The roots of "ltrasoni tehnology an be traed bak to researh on thepieoeletri effet ond"ted by -ierre *"rie aro"nd /@@0.

• He fo"nd that asymmetrial rystals s"h as ,"art and :ohelle salt

(potassi"m sodi"m titrate) generate an eletri harge when mehanialpress"re is applied.

• *onversely# mehanial vibrations are obtained by applying eletrialosillations to the same rystals.

• 9re,"eny val"es of "p to /6h (/ billion yles per seond) have been

"sed in the "ltrasoni ind"stry.

• Todays ltrasoni appliations inl"de medial imaging (sanning the"nborn fet"s) and testing for raks in airplane onstr"tion.



ltrasoni aves

• The ltrasoni waves are so"nd waves of fre,"eny higher than

10#000 H.

• ltrasoni waves an be generated "sing mehanial# eletromagneti

and thermal energy so"res.

• They an be prod"ed in gasses (inl"ding air)# li,"ids and solids.

• agnetostritive transd"ers "se the inverse magnetostritive effet toonvert magneti energy into "ltrasoni energy

• This is aomplished by applying a strong alternating magneti field to

ertain metals# alloys and ferrites



ontinue..

• -ieoeletri transd"ers employ the inverse pieoeletri effet

"sing nat"ral or syntheti single rystals (s"h as ,"art) or

eramis (s"h as bari"m titanate) whih have strong

pieoeletri behavior.

• *eramis have the advantage over rystals in that they are

easier to shape by asting# pressing and e!tr"ding.



/&This is the standard mechanism used in most of the universalUltrasonic machines



• %n the proess of ltrasoni ahining# material is removed by miro&hipping or erosion with abrasive partiles.

• %n $ proess# the tool# made of softer material than that of the

workpiee# is osillated by the Booster and $onotrode at a fre,"eny of

abo"t 10 kH with an amplit"de of abo"t 1;.4 "m (0.00/ in).

• The tool fores the abrasive grits# in the gap between the tool and the

workpiee# to impat normally and s"essively on the work s"rfae#

thereby mahining the work s"rfae.

• 8"ring one strike# the tool moves down from its most "pper remoteposition with a starting speed at ero# then it speeds "p to finally reah

the ma!im"m speed at the mean position.

Principle of machining



ontinue..

$ Then the tool slo1s do1n its speed and eventually reaches 0ero again at thelo1est position.

$ 6hen the grit si0e is close to the mean position/ the tool hits the grit 1ith its

full speed

$ The smaller the grit si0e/ the lesser the momentum it receives from the tool.

$ Therefore/ there is an effective speed 0one for the tool and/ correspondingly

there is an effective si0e range for the grits.

$ 'n the machining process/ the tool/ at some point/ impacts on the largest grits/

1hich are forced into the tool and 1or2 piece.



ontinue..

$ 3s the tool continues to move do1n1ards/ the force acting on these gritsincreases rapidly/ therefore some of the grits may (e fractured.

$ 3s the tool moves further do1n/ more grits 1ith smaller si0es come in contact1ith the tool/ the force acting on each grit (ecomes less.

$ %ventually/ the tool comes to the end of its stri2e/ the num(er of grits underimpact force from (oth the tool and the 1or2piece (ecomes ma)imum.

$ Grits 1ith si0e larger than the minimum gap 1ill penetrate into the tool and1or2 surface to different e)tents according to their diameters and the hardnessof (oth surfaces



?letrohemial ahining

• ' pop"lar appliation of eletrolysis is the electroplating proess in

whih metal oatings are deposited "pon the s"rfae of a atholially

polaried metal.

• ?* is similar to eletro polishing in that it also is an anodidissol"tion proess. B"t the rates of metal removal offered by the

polishing proess are onsiderably less than those needed in metal

mahining pratie .



*onept

•etal removal is ahieved by eletrohemial dissol"tion of an anodially

polaried workpiee whih is one part of an eletrolyti ell in ?*.

• when an eletri "rrent is passed between two ond"tors dipped into a

li,"id sol"tion named as ?letrolysis .

• ?letrolytes are different from metalli ond"tors of eletriity in that the

"rrent is arried not by eletrons b"t by atoms# or gro"p of atoms# whih

have either lost or gained eletrons# th"s a,"iring either positive or

negative harges. $"h atoms are alled ions.



?letrolyti dissol"tion of iron.



ontinue..

$ 'ons 1hich carry positive charges move through the electrolyte in the

direction of the positive current/ that is/ to1ard the cathode/ and are called

cat anions.

$ The negatively charged ions travel to1ard the anode and are called anions.

$ The movement of the ions is accompanied (y the flo1 of electrons/ in theopposite sense to the positive current in the electrolyte.

$ Both reactions are a consequence of the applied potential difference/ that is/

voltage/ from the electric source.



ontinue..

• the workpiee and tool are the anode and athode# respetively# of

an eletrolyti ell# and a onstant potential differene# "s"ally at

abo"t /0 V# is applied aross them.

• ' s"itable eletrolyte# for e!ample# a,"eo"s sodi"m hloride (table

salt) sol"tion# is hosen so that the athode shape remains

"nhanged d"ring eletrolysis.

• The eletrolyte is also p"mped at a rate 3 to 30 meter<seond#

thro"gh the gap between the eletrodes to remove the prod"ts of

mahining and to diminish "nwanted effets# s"h as those that

arise with athodi gas generation and eletrial heating.

• The rate at whih metal is then removed from the anode is

appro!imately in inverse proportion to the distane between the

eletrodes



ontinue..

• 's mahining proeeds# and with the sim"ltaneo"s movement of the

athode at a typial rate# for e!ample# 0.01 millimeter<seond toward

the anode.

• the gap width along the eletrode length will grad"ally tend to asteady&state val"e. nder these onditions# a shape# ro"ghly

omplementary to that of the athode# will be reprod"ed on the

anode.



Schematic diagram



?* *omponents (-ower)

• The power needed to operate the ?* is obvio"sly eletrial. Thereare many speifiations to this power.

• The "rrent density m"st be high.

• The gap between the tool and the work piee m"st be low for higher

a"ray# th"s the voltage m"st be low to avoid a short ir"it.

• The ontrol system "ses some of this eletrial power.

?* * t



?* *omponents

(eletrolyte ir"lation system,

• The eletrolyte m"st be in+eted in the gap at high speed (between

/;00 to 3000 m<min).

• The inlet press"re m"st be between 0./;&3 -a.

• The eletrolyte system m"st inl"de a fairly strong p"mp.

• $ystem also inl"des a filter# sl"dge removal system# and treatment

"nits.

• The eletrolyte is stored in a tank.



%M omponents +control system,

• *ontrol parameters inl"de>

C Voltage

C %nlet and o"tlet press"re of eletrolyte C Temperat"re of eletrolyte.

• The "rrent is dependant on the above parameters and the feed

rate.

d



3dvantages

• There is no "tting fores therefore lamping is not re,"ired

e!ept for ontrolled motion of the work piee.• There is no heat affeted one.

• Very a"rate.

• :elatively fast

• *an mahine harder metals than the tool

• 9aster than ?8

• o tool wear at all.

• o heat affeted one.

• Better finish and a"ray.



Disadvantages

• ore e!pensive than onventional mahining.

• eed more area for installation.

• ?letrolytes may destroy the e,"ipment.

• ot environmentally friendly (sl"dge and other waste)

• High energy ons"mption.• aterial has to be eletrially ond"tive.



Prod cts



Products

• The two most ommon prod"ts of ?* are t"rbine<ompressor

blades and rifle barrels.

• ?ah of those parts re,"ire mahining of e!tremely hard metals with

ertain mehanial speifiations that wo"ld be really diffi"lt to

perform on onventional mahines.

• $ome of these mehanial harateristis ahieved by ?* are> C $tress free grooves.

C 'ny groove geometry.

C 'ny ond"tive metal an be mahined.

C :epeatable a"ray of 0.000;D.

C High s"rfae finish.

C 9ast yle time.



%conomics

• The proess is eonomial when a large n"mber of omple!idential prod"ts need to be made (at least ;0 "nits).

• $everal tools o"ld be onneted to a assette to make many

avities sim"ltaneo"sly. (i.e. ylinder avities in engines).

• 5arge avities are more eonomial on ?* and an be proessed

in /</0 the time of ?8.



?5?*T:E*H?%*'5 6:%8%6

t



oncept

• The main feat"re of eletrohemial grinding (?*6) is the "se of a

grinding wheel in whih an ins"lating abrasive# s"h as diamondpartiles# is set in a ond"ting material. This wheel beomes the

athode tool .

• The non ond"ting partiles at as a spaer between the wheel and

workpiee# providing a onstant inter eletrode gap# thro"gh whih

eletrolyte is fl"shed. • '"raies ahieved by ?*6 are "s"ally abo"t 0./1; millimeter. '

drawbak of ?*6 is the loss of a"ray when inside orners are

gro"nd. Bea"se of the eletri field effets# radii better than 0.1; �

0.3F; millimeter an seldom be ahieved • ' wide appliation of eletrohemial grinding is the prod"tion of

t"ngsten arbide "tting tools. ?*6 is also "sef"l in the grinding of

fragile parts s"h as hypodermi needles



oncept

• *ombines eletrohemial mahining with onventional grinding.

• The e,"ipment "sed is similar to onventional grinder e!ept that the

wheel is a rotating athode with abrasive partiles.

• The wheel is metal bonded with diamond or 'l o!ide abrasives.

• 'brasives serve as ins"lator between wheel and work piee. ' flow of

eletrolyte (sodi"m nitrate) is provided for eletrohemial mahining.

• $"itable in grinding very hard materials where wheel wear an be veryhigh in traditional grinding

S l %M d t



Sample %Med parts

unconventional

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