Worm Wheel
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Transcript of Worm Wheel
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Material Science and
Metallurgy(2131904)
Open Ended Problem
Academic ear 201!"1#
(3rdSem)
Batch : 1A19
Branch : Mechanical (class-1)
Topic : Gears (Spur, Helical, Bevel,
Worm)
Spur $ear: 1!11!119!-!1 to
1!11!119!-!"%elical $ear:1!11!119!-!# to
1!11!119!-1$
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&e'el $ear 1!11!119!-1% to
1!11!119!-1&
orm $ear 1!11!119!-19 to1!11!119!-$$
O*M $EA*(1!11!119!-19 to 1!11!119!-$$)
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Photo courtesy Emerson PowerTransmission Corp.
&a+ic *e,uirement o- orm $ear
Worm 'ears are use hen lar'e 'earreuctions are neee*
http://www.emerson-ept.com/http://www.emerson-ept.com/http://www.emerson-ept.com/http://www.emerson-ept.com/ -
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+t is common or orm 'ears to havereuctions o $!:1, an even up to %!!:1 or
'reater*
The orm can easil turn the 'ear, .ut the 'ear
cannot turn the orm* This is .ecause the an'le
on the orm is so shallo that hen the 'ear
tries to spin it, the riction .eteen the 'ear an
the orm hols the orm in place*
This eature is useul or machines such as
conveor sstems, in hich the loc/in' eature
can act as a .ra/e or the conveor hen the
motor is not turnin'*
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Material+ .+ed in orm /it it+
Application+
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Material 0otes Applications
Worm
Acetal 0lon
2o 3ost, lo utTos, omesticappliances,instruments
3ast +ron45cellentmachina.ilit,
meium riction*
6se inre7uentlin moern
machiner
3ar.onSteel
2o cost,reasona.lestren'th
8oer 'ears ithmeium ratin'*
HareneSteel
Hi'h stren'th, 'ooura.ilit
8oer 'ears ithhi'h ratin' ore5tene lie
Wormheel
Acetal0lon
2o 3ost, lo utTos, omesticappliances,instruments
8hosBrone
easona.lestren'th, lo
riction an 'oocompati.ilit ithsteel
0ormal material ororm 'ears ithreasona.lee;cienc
3ast +ron45cellentmachina.ilit,meium riction*
6se inre7uentlin moernmachiner
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Material Specication /it Proper
ame
Worm 'ear sets are usuall use to reuce speean increase tor7ue* Since the orm riveuner'oes more contact stress ccles than theorm 'ear, the orm rive is usuall o a stron'ermaterial*a+t ironprovies ura.ilit an ease o
manuacture*
Alloy +teelprovies superior ura.ilit an
corrosion resistance* Minerals ma .e ae tothe allo to urther haren the 'ear*
a+t +teelprovies easier a.rication, stron'
or/in' loas an vi.ration resistance*
arbon +teel+are ine5pensive an stron', .ut
are suscepti.le to corrosion*
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Aluminumis use hen lo 'ear inertia ith
some resilienc is re7uire*
&ra++is ine5pensive, eas to mol ancorrosion resistant*opperis easil shape, conuctive an
corrosion resistant* The 'ear
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Propertie+ o- SAE #! So, rom these it is clear that .rone is the
most appropriate material or orm*
An SA4 "> is 'enerall most common use
material or orm
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Manu-acturing Proce++ *e,uired
-or orm
Material Selection
The inuction process onl re7uires a errous
material to create heat in the or/* To haren
steel, hoever, re7uires an allo ith relativel
hi'her car.on amounts* 3omon steels use in this processin' or
proucin' 'ear orms are 1>! or 1!>!* The
latter is less e5pensive .ut has a loer
machina.ilit*Tpicall, allos havin' 3ar.on levels o !*-
!*" 3ar.on oCer e5cellent inuction
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harenin' characteristics or .oth epth an
pattern*Depenin' on the harness level or tolerances,
a variet o steels are availa.le that oCer 'ooinuction harenin' a.ilit*The machina.ilit o the steel is ver important
in this processin', .ecause the orm is .ein'
@nishe ith a cuttin' process, so surace
rou'hness is critical*Since orms tpicall run ith .rass or .rone
'ears, ear is critical* The smoother the surace the .etter the lie o
the 'ear* 1"rms (!*a) is possi.le an not
unhear o .ut $!-$rms is more tpical an
controlla.le*
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orm Production Metod+
The e5act orm o the orm teeth is a unction othe metho use to @nish the teeth* Worms ma
.e mille in a threa miller or similar machine,
usin' a ou.le conical millin' cutter havin' an
inclue an'le e7ual to to times the pressure
an'le o the orm* Worm tooth 'rinin' is
usuall one in a threa 'rinin' machine, usin'
a 'rinin' heel resse ith a ou.le conicalorm* The orm teeth ma also .e prouce .
usin' a sin'le-point tool in a lathe* This is the
same metho use or cuttin' scre threas*
8rouction 7uantities o @ne pitch orms oten
have the teeth prouce . rollin', usin' the
same tpe o e7uipment use or rollin' scre
threas* Multiple-threa orms are oten
prouce . ho..in', 'eneratin' the teeth as a
helical 'ear* Aitionall, e7uipment is availa.le
or @nishin' orm teeth . 'rinin' one tooth
Ean/ at a time, usin' the Eat sie o a 'rinin'
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heel* Machines are also availa.le emploin' the
same principles or millin' teeth* This sstem is
most commonl use on lar'e orms*
Worm Wheel 8rouction Worm heel teeth are
most commonl prouce . ho..in'* To
methos are commonl useFthe raial
ineemetho or the tan'ential ee metho*
4ither metho can .e use to prouce a throate
orm heel* Beore the ho. can .e esi'ne anmanuacture, it is necessar that the ho.
esi'ner .e provie ith inormation a.out the
orm prouction metho, an etails o the
orm tooth pro@le, in orer that the ho. can
prouce a orm heel ith a tooth pro@le
conu'ate to the orm*
A) *adial in-eed obbing
aial inee ho..in' is most commonl use or
orm heels havin' a relativel lo lea an'le,
an or commercial 'rae proucts* There are a
lar'e num.er o orm 'ear sets manuacture to
replace ama'e or orn e7uipment* Man o
these are mae in plants that on
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accurac o the tooth pro@le, hich is 'enerate
as a num.er o Eats or acets* aial inee
ho..in' is 'enerall consiere to .e the most
economical metho o orm heel prouction*
&) angential obbingTan'ential ho..in' is 'enerall the preerre
metho or proucin' orm heels havin' hi'h
lea an'les, an 'ears re7uirin' particularl
accurate tooth pro@les* +t is necessar to use a
ho..in' machine e7uippe ith iCerential
'earin', so that the ho. is e lon'ituinall
alon' its a5is as it revolves* The ho. is esi'ne
ith a tapere section an a clinrical section*
The tapere portion o the ho. rou'hs the teeth,
an as the ho. avances, the clinrical section
o the ho. @nishes the teeth* The com.ination othe rotar an a5ial motion creates a conition
similar to usin' a ho. ith man cuttin' Eutes*
As a result o this the tooth pro@le consists o a
'reat man ver small Eats, more nearl
appro5imatin' the theoretical tooth pro@le*
) 5y obbing l cuttin', or E ho..in', is another metho
that is use to manuacture orm heels* This
uses a cuttin' tool that is essentiall one
@nishin' tooth rom a ho., mounte in a suita.le
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holer on the ar.or o a ho..in' machine
e7uippe or tan'ential ho..in'* This one tooth
is traverse throu'h the or/, tan'entiall* The
cuttin' tool is usuall reerre to as a =E cutter=or =E tool*= The tool ill rou'h an @nish the
orm heel in a sin'le pass, e5cept in cases
here the num.er o teeth in the 'ear an the
num.er o threas in the orm have a common
actor* +n these cases the E tool ill have to .e
ine5e or each threa in the orm until the
orm heel is complete*
*e-erence+
A0S+AGMA $!11-A9& 3linrical Worm'earin'Tolerances an +nspection Methos, American
Gear Manuacturers Association, 199&*