Worm Wheel

7/25/2019 Worm Wheel

1/17

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$


2/17

&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!-$$)


3/17

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/


4/17

+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'*


5/17

Material+ .+ed in orm /it it+

Application+


6/17

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


7/17

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*


8/17

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


9/17


10/17

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


11/17


12/17

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


13/17

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*


14/17

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'


15/17

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


16/17

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


17/17

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&*

Documents

Worm Wheel