Design of Machine Elements Project

8/15/2019 Design of Machine Elements Project

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P R E S E N T E D B Y :

DESIGN OF MACHINEELEMENTS PROJECT

Girish Chandankar


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GEOMETRIC TOLERENCING

Geometric to erances are taken into acco!nt on " #hen the si$e and sha%e needed to &e contro edmore %recise " #hi e 'ormin( a com%onent

The" are !sed on " #hen the sha%e or 'orm has a%artic! ar '!nction and errors #o! d res! t in %oor%er'ormance)Geometric to erances are a%% ied in addition to

dimensiona to erances)


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DEFENITION

Geometric dimensioning and tolerancing(GD&T) is a symbolic language used on

engineering dra ings and com!utergenerated t"ree dimensional solid models‐#or e$!licitly describing nominal geometryand its allo able %ariation

GD*T s"m&o s a o# a desi(n en(ineer to %recise "and o(ica " descri&e %art 'eat!res in a #a" the" can &e acc!rate " man!'act!red and ins%ected)


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+H, SHO-LD GD*T .E -SED/

It is a sim% e and e''icient method 'or descri&in( theto erancin( mandated &" the desi(ner o' the %art)It sim% i'ies ins%ection &eca!se hard (a(es can o'ten

&e !ti i$ed and ins%ection 'i0t!res are o'tenmandated #hich sim% i'ies ins%ection 'or %rod!ction1!antities)It 'orces the desi(ner to tota " consider '!nction2

man!'act!rin( %rocess2 and ins%ection methods


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S,M.OLS

The s"m&o s are !sed to contro the (eometricasha%e and 'orm o' a com%onent are themse 3essim% e &!t their a%% ication needs to considered

care'! " As stated ear ier the !se o' s"m&o s sho! d &e done #ith care since the a%% ication o' to erence s"m&oto contro a 'eat!re or sha%e ma" a''ect the contro o'

the another)E0am% e444444the !se o' %ositiona to erance ma"a so contro strai(htness and ' atness)


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TA.LE FOR S,M.OLS


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De'enition indication o' to erance $one and inter%retation o'to erance $one

STRAIGHTNESS5 A strai(htness to erances%eci'ied a to erance $one

#ithin #hich an a0is ore ement m!st ie Fi()Strai(htness is a

condition in #hich ane ement o' a s!r'ace oran a0is is a strai(ht ine)


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FLATNESS5 A ' atness to erances%eci'ies a to erance $one

de'ined &" t#o %ara e % anes #ithin #hich the s!r'acem!st ie 6Fi( 789) F atness is

the condition o' a s!r'aceha3in( a e ements in one% ane)


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RO-NDNESS5 A ro!ndness 6circ! arit"9 to erance s%eci'ies a to erance $one &o!nded &" t#oconcentric circ es #ithin each circ! ar e ement o' the s!r'ace m!st ie) Ro!ndnessis a condition o' a s!r'ace o' re3o !tion in #hich2 'or a cone or c" inder2 a %ointso' the s!r'ace intersected &" an" % ane %er%endic! ar to a common a0is aree1!idistant 'rom that a0is)


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C,LINDRICIT,5 A c" indricit" to erance s%eci'ies a to erance $one &o!nded &" t#o

concentricc" inders #ithin #hich the s!r'ace m!st ie) C" indricit" is a condition o' a

s!r'aceo' re3o !tion in #hich a %oints o' the s!r'ace are e1!idistant 'rom a

common a0is )


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ANG-LARIT,5 An An(! arit" to erance s%eci'ies ato erance $one de'ined &" t#o %ara e

% ane at the s%eci'ied &asic an( e 6otherthan :8O9 'rom a dat!m % ane or a0is #ithin #hich the s!r'ace or the a0is o' the 'eat!re m!st ie)


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PARALLELISM5 A Para e ism to erance s%eci'ies a to erance $one de'ined &" t#o %ara e

% ane orines %ara e to a dat!m % ane or a0is2 res%ecti3e "2 #ithin #hich the

s!r'ace ora0is o' the 'eat!re m!st ie)


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A Para e ism to erance s%eci'ies a to erance $one s%eci'" ac" indrica to erance

$one %ara e to a dat!m a0is2 #ithin #hich the a0is o' the'eat!re m!st ie)


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Per%endic! arit"5 A Per%endic! ar to erance is a condition o' a s!r'ace2median

% ant2 or a0is at :8Oto a dat!m % ane or a0is)


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CONCENTRICIT,5Concentricit" is a conditionin #hich the a0es o' across4section e ements o' a'eat!re;s s!r'ace o'

re3o !tion are common tothe a0is o' a dat!m'eat!re) A concentricit" to erance s%eci'ies ac" indrica to erance $one #hose a0is coincides #ith adat!m a0is and #ithin #hicha cross4sectiona a0es o' the 'eat!re &ein(contro ed m!st ie)


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S!r'ace 'inish * s"m&o


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Introd!ction

S ' R * E + N + S , - . S / 0 N / 1 N S S ' R * ET E 2 T ' R E - + S T, E * , R * T E R + S T + * S / S ' R * E+ T , S T, R E E * / 3 P / N E N T S :

. Y

S ' R * E R / ' G , N E S S 1 4 + N E S S


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Im%ortance

The Im%ortance o' S!r'ace Finish in Com%onents 'or The Aeros%ace and Medica Ind!stries Introd!ction In theaeros%ace and medica 'ie ds the s!r'ace 'inish o' machinedcom%onents is o' !tmost im%ortance) Hi(h %ress!reh"dra! ic s"stems and '!e in


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S"m&o s * s%eci'ication

S"m&o are !sed to re%resent the t"%e * de(ree o's!r'ace 'inish on en(ineerin( dra#in()Dimensions o' s"m&o s


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T"%es o' s"m&o * descri%tion


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De'initions

S!r'ace te0t!re5 inc !des ro!(hness2 #a3iness2 a" and ' a#s)Pro'i e5 is the conto!r 6sha%e9 o' a s!r'ace in a % ane %er%endic! ar tothe s!r'ace)Micrometer =>? 5 7@784 m B 7 7888888 mRo!(hness5 sma %eaks and 3a e"s 'o!nd in the s!r'ace 6'ineirre(! arities9Ro!(hness hei(ht5 arithmetica a3era(e de3iation =>?)

• Roughness width: distance between two peaks that make the roughne• Waviness: larger deviation from the nominal surface on which the

roughness is superimposed• Waviness height: distance from peak to valley• Waviness width: distance between successive wave peaks or successi

wave valleys.• Lay: directions of tool marks, or grains of surface• Flaw: surface defects.


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S"m&o s%eci'ication * %arameters


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E0am% e o' s!r'ace 'inish dra#in(


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Methods to check s!r'ace 'inish


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Res! ts o' s!r'ace 'inish testin(


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Limits and Fits


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In en(ineerin( "o! are !s!a " concerned #ith a n!m&er o'%arts or com%onents 'ittin( to(ether to make an assem& "To assem& e com%onents to(ether en(ineers m!st controthe si$es o' the com%onents to make s!re that the" 'itto(ether correct ")

I' the" don;t 'it to(ether correct " then the com%onents #inot '!nction %ro%er ")

Introd!ction

assembly


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+hat is a FIT in en(ineerin( terms/


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irst consider "at is re5uired o# t"e #it

T"en decide "o muc" clearance orinter#erence you are going to gi%e your #it

T"en determine "at nominal si6e youare going to #it toget"er

Ho# do #e decide #hich 'it to !se/


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The" are &asica " an" si$e2 it ma"&e an" #ho en!m&er "o! ike5 4

78 79 ; 8; 79;; 9


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d%antages o# "a%ing a system:+nterc"angeable > %arts made at di''erent times or % aces

'it to(ether)

Time sa%ing > re'erence to a standard s"stem s%eeds !%decisions on si$es to (i3e %artic! ar 'its)

ssurance o# correct #it > act!a 'it #i &e as re1!irede3en i' desi(n si$e chan(es)

S!are Parts ? man!'act!re o' these is made easier as the"can &e made to the same standard)

+e need a s"stem to he %


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-ses the nominal si6e 'or &oth ho es andsha'ts)This si$e is determined &" stren(thconsiderations)Ca c! ations o' materia %ro%erties andstren(ths are !sed to o&tain the nomina si$e)

Remember: The nomina si$e is the same'or &oth ho e and sha't)

.ritish Standards 88


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The .ritish Standard S"stem !ses the etters o' thea %ha&et to descri&e ho# m!ch &i((er or sma er aho e or a sha't #i de3iate 'rom the nomina si$e)

This de3iation is ca ed the54 undamental de%iation

Ho es are descri&ed &" ca%ita etters H2 G etc)Sha'ts are descri&ed &" o#er case etters h2 ( etc)

.S 88


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ero ine A .

The F!ndamenta De3iation

H M

T"eundamental

De%iation

T"e

undamentalDe%iation

Nomina Si$e

T"e,oles


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T"e S"a#ts

Nomina Si$e

ero Line

F!ndamenta De3iation

F!ndamenta De3iationNomina Si$e

a

& ( m e


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M

A

An" com&ination o' ho e and sha't can &e !se

e

A e 'it

aSo &e care'! #hen

choosin( "o!r 'its the"don;t a #ork

M a 'it


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.ritish Standards To erance $onesTolerance @one

.S 88 !se n!m&ered to erance $ones 687 to 7 9


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The most acc!rate to erance $ones aren!m&ered 87 8 and 8 )

+hereas 'or more (enera en(ineerin( #ork #e !se 8 2 8K and 8 )

Fina "2 ro!(h #ork is done at 7 27 and 7 )

.ritish Standards To erance $ones

+n engineering e donAt use t"e 6eros


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,o! no# ha3e a etter and a n!m&er)

P!t them to(ether and "o! ha3e the t"%e o' 'itand the to erance that #i achie3e it) E0am% esare5

• HK2 and M:)•

For ho es )For sha'ts #e !se5( 2 hK and 'K)

Ro!nd !%


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,ere t"en is t"e com!lete #it:

T"e ,ole T"e s"a#t

H: 'K


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.S 88


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Look on the chartMa0im!m and minim!m a o#ances are sho#n in

tho!sandths o' a mi imetre

Minim!m c earance and minim!m inter'erence isminim!m ho e si$e min!s ma0im!m sha't si$eTo erance is ma0 de3iation min!s min de3iation

Limits o' si$e


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hank "o!

Design of Machine Elements Project

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