Mech 424 Lecture 72007

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DFA, DFM, & DFMA 1

DFA, DFM, & DFMA 1

Lecture 7

The contents of this lecture are the sole copyright of M. Ham & J. Jeswiet

They are intended for use only by students in MECH 424 !ife Cycle Engineering

"ueen#s $ni%ersity ingston '( Canada.

Unlicensed use of the contents of this lecture outside MECH 424 is illegal .

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The topic for today is

DFA, DFM & DFMA

The topic for today is

DFA, DFM & DFMA

From the BDI BDI website

BBoothroyd & DDewhurst I I nstitute

website

DFA/DFM/DFMA is

supposed to:

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What is DFA/DFM/DFMA

• DFA – how easy things go together – DFA: Design of components taking into account how they will be

assembled together to ensure that assembly costs areminimied!

• DFM – how easy things can be made – DFM: Design of components taking into consideration the

processes that will be used to manufacture them to ensure thatmanufacturing costs are minimied!

• DFMA – balance between ease of making " assembly – DFMA: #t is ob$ious that these two goals are often incompatible

and hence compromises must be made!• Environmental factors are not directly taken into account,Environmental factors are not directly taken into account,

improved uality ! reduced "aste, and thus does indirectlyimproved uality ! reduced "aste, and thus does indirectlyimpact the environment#impact the environment#

• DFD – how easy things take apart

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DFA DFM DFMA DFE

DF$

DFD

DF$$

DFA ! desi%n for assemlyDFM ! desi%n for manufacture

DFE ! desi%n for Environment

DFD ! desi%n for disassemly

DF$ ! desi%n for service

DF$$ ! desi%n for si' si%ma

DF( ! desi%n for (

)ro%ression of the development of DFMA* how it developed

DF(+s

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%roduct &osts

i%hest impact on reducin% cost - reducin% parts


BBoothroyd & DDewhurst I I nstitute website

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&ost 'eduction (pportunities

DFA

DFM

DFMA



simplifyin%simplifyin%

&&

reducin%reducin%

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Model )

Early DFA

• *hipping crates forfloorboards

• %aint colour

• Assembly +ine

• (perating Door

• &hoke

http://www.hfmgv.org/exhibits/showroom/1908/tbig.jpg

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.n 1/0/, .n%ersoll2and not only cut product development time in half

ut also reduced the numer of parts needed3

2esults of .n%ersoll2and pro4ect "ith DFMA

5efore After

6ompressoroil cooler parts

0808 9/9/

:umer offasteners

;0;0 9898

:umer ofassemlyoperations

1

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Ford $s! ,M ?5oothrotd & De"hurst, 1///@

• Front -umper of )aurus .after DFA

– 01 parts

• Front -umper of ,rand %ri2 – 011 parts

• 304 producti$ity gap – due to ease of

assembly• Ford5s parts fit together easier

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.n a survey of 0/ industries "ho used DFMA

it "as found that the follo"in% reductions "ere achieved, on

avera%e

188



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5oothroyd and De"hurst look at this as follo"s*



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modern methods of analysis

traditional vie"* B"e desi%n it, you uild itC, ?still prevalent today@

chan%in% attitudes ?more team"ork@

hy "ere these improvements suddenly possile and not efore

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13 6oncurrent En%ineerin%

13 2educe Manufacturin% & Assemly 6osts

93 2educe Time to Market

;3 2educe Desi%n 6osts=3 Etc3

93 5enchmarkin% 6ompetitors )roducts

;3 Analyin% $upplier 6osts

13 Most contracts have a clause to reduce costs

annually

Ways to Use DFMAWays to Use DFMAWays to Use DFMAWays to Use DFMA

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Manual

Most fle'ile & Most e'pensive

$kill of "orkers effects assemly times

ard Automation

6ustom toolin% - only make one product

$oft Automation

2oots

More de'terity 5GT dum

Types o Assembly Types o Assembly Types o Assembly Types o Assembly

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13 2educe numer of parts

93 2educe numer of different parts $tandardie parts;3 $implification of assemly

=3 2eduction numer of processes

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13 durin% operation of the product, does the part move relative to all

other parts already assemled

Hnly %ross motion should e consideredI small motions can e

accommodated y other means such as inte%ral elastic elements3

93 must the part e of a different material than or e isolated from all

other parts already assemled

Hnly fundamental physical needs for material differences are

acceptale3

;3 must the part e separate from all other parts already assemled

The only reason to have it separate "ould e that assemly or

disassemly ?for maintenance reasons H:LJ@ of other separate parts

"ould e impossile3

The three "riteriathree "riteria a%ainst "hich a part must e

e'amined, as it is added to the product assemly, are*

#ustii"ation o $art #ustii"ation o $art #ustii"ation o $art #ustii"ation o $art

Th t t l k t thi i ith l

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The est "ay to look at this is "ith an e'ample3

6onsider a motor drive assemly that is reuired to sense and

control its position on t"o %uide rails, as sho"n schematically*

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)roposed desi%n of a motor drive assemly)roposed desi%n of a motor drive assemly

A li ti f th th it i i

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Application of the three criteria %ives*

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From the fore%oin% analysis it can e seen that*

if the motor and sensor suassemlies could e arran%ed to snap or

scre" into the ase and

if a plastic cover could e desi%ned to snap on,

in theory, there "ould e only four parts needed instead of nineteen3

The ore%oin% was done without "onsiderin% any pra"ti"al limitations

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The Desi%ner andor desi%n team is no" placed in a position of havin% to

ustiy the e'isten"e o the parts ustiy the e'isten"e o the parts that did not satisfy the DFA criteria3

Kustification comes from practical, technical or economic considerations3

For e'ample* it could e ar%ued that t"o scre"s are needed to secure the

the motor and one scre" is needed to position the sensor ecause any

alternatives are impractical for a lo" volume operation such as this3

o"ever the desi%n of the scre"s could e improved y providin% them

"ith Bpilot pointsC to facilitate assemly3

5ased upon the fore%oin% some desi%n rules can already e estalished3

Advanta%e in the Desi%n )rocess*

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(ome Desi%n )ules * lo%i"al

A common theme throu%hout DFAcommon theme throu%hout DFA, is the need to

reduce the numer of fastenin% devices, "ith scre"s

ein% the main culprit

if scre"s are used, one standard sie should e used

all scre" heads should e the sameI

a common scre" driver can then e used

all scre"s should have pilot points to facilitate easier

assemly

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The follo"in% chan%e could easily e made*

the po"der metal ushin%s are unnecessary ecause the part can

e machined from an alternative material "ith the ri%ht frictional

characteristics, such as :ylon

The follo"in% are difficult to 4ustify*

separate standoffs

end plate

cover

the si' scre"s

e started "ith this3

5efore %oin% further it is necessary to have estimates of

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5efore %oin% further it is necessary to have estimates of

assemly times

costs

Techniues are availale to make these estimates ut "ill not e dealt"ith here3

$uffice it to say "e can estimate the times and costs sho"n in the ne't

tale3

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5oothroyd and De"hurst do one thin% at this point that is particular

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5oothroyd and De"hurst do one thin% at this point that is particular

to their DFMA analysis3

They calculate the BManual Assembly +i"ien"y, + maC

here - min ! the theoretical part minimum

t a ! the theoretical, lo"est assemly time3

this is an ideal minimum

t ma ! the estimated assemly time to complete assemly of

the actual product

.t should e noted these criteria are applied "ithout takin% %eneral

desi%n considerations into account3

E N t

t m a

a

m a

= m i nThis is done "ith the euation*

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"here

- min ! = parts,

t ma

! 1>8 sec,

t a . ;3< sec

As an example:

the desi%n efficiency for the motor drive is, E N t

t

m a

a

m a

= m i n

Then and E ma = 8.8% E m a = •4 3 5

1 6 0

.

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.t can e seen that those parts that didn+t meet the criteria for the

minimum part count involved a total assemly time of 1983> seconds

)able 0

theoretical assembly assembly

no! part count time6 sec cost .centsbase 0 0 7!8 9! )he assembly cost is for a

bushing 9 1 09!7 01!9 labour rate of ;71 per hour

motor sub 0 0 !8

motor screw 9 1 90 0

sensor sub 0 0 =!8

set screw 0 1 01!> =!=stand?off 9 1 0> 07!7

end plate 0 0 =!3 < Design @fficiency =!=4

end plate screw 9 1 0>!> 07!=

plastic bus 0 1 7!8 9! )ime for parts deleted 091!>

thread leads 8 3!9 in ideal situation6 sec

reorient 3!8 7!=

co$er 0 1 !3

co$er screw 3 1 70!9 9> for redesign6 sec

2edesi%ned motor after analysisI

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2edesi%ned motor after analysisI

t"o motor mount scre"s have een kept

'esults for DFA analysis for redesign of Motor dri$e assembly

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base 0 0 7!8 9!

motor sub 0 0 3!8 7!=

motor screw 9 1 09 01sensor sub 0 0 =!8

set screw 0 1 =!8

thread leads 8 3!9

plastic co$er 0 0 3 7!7

)otals < 3 3> 7=!3

Design efficiency 9>4 )his percentage approaches the range found6

from e2perience6 for electro?mechanical de$ices

*a$ings in assembly cost 1!8;#ncrease in design efficiency 73=4

'esults for DFA analysis for redesign of Motor dri$e assembly

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At the end of the chan%es

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At the end of the chan%es

due to DFMA are*

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13 2educe numer of parts

93 2educe numer of different parts $tandardie parts;3 $implification of assemly

=3 2eduction numer of processes

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• (ne )ime &osts – )ooling – Design/De$elopment – &ontacting / Bendor *election

– %roduct )esting

• &ontinuous &osts – Material – Assembly

– #n$entory – #nspection

)edu"e number o dierent parts *)edu"e number o dierent parts *

(tandardie parts(tandardie parts

)edu"e number o dierent parts *)edu"e number o dierent parts *

(tandardie parts(tandardie parts

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• @asier faster

• +ess opportunity for mistakes

• @asier to automate

(implii"ation o Assembly (implii"ation o Assembly (implii"ation o Assembly (implii"ation o Assembly

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• +ess steps faster

• +ess material handling less damage

• +ess operations less opportunity fordefects

• Balue Added processes in C remo$e on?

Balued Added steps

)edu"tion -umber o $ro"esses)edu"tion -umber o $ro"esses)edu"tion -umber o $ro"esses)edu"tion -umber o $ro"esses

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0ess Fasteners0ess Fasteners

espe"ially s"rews & boltsespe"ially s"rews & bolts

0ess Fasteners0ess Fasteners

espe"ially s"rews & boltsespe"ially s"rews & bolts

Left to ri%ht* simplest, lo" cost to most parts hardest to assemly

BBoothroyd & DDewhurst I I n", 1222

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• )akes time toseparate

• 'eEuires people• ard to automate

)edu"e Tan%lin% / -estin% )edu"e Tan%lin% / -estin% )edu"e Tan%lin% / -estin% )edu"e Tan%lin% / -estin%

3u%h #a"4 3u %h #a"4 , 5661

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• ow does this fit it in with M@& 393G

• ow does this fit into @ngineeringG

(o What7 (o What7 (o What7 (o What7

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13 6ritical orientation - ovious - see & fit

93 :oncritical orientation - fit in any direction

8rientation8rientation8rientation8rientation

&

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+nsure A""ess & 9isibility +nsure A""ess & 9isibility +nsure A""ess & 9isibility +nsure A""ess & 9isibility

www!uniontire!ca/tireassfr!htmwww.detnews.com/2004/project/0405/04/901-134795.htm

+asy part handlin%+asy part handlin%

+asy part handlin%+asy part handlin%

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• *ie

• Weight

• *hape• *harp edges

• *ticky

• )angled " ested• etc!

+asy part handlin% +asy part handlin% +asy part handlin% +asy part handlin%

/) d l ti / li t ti

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)edu"e lo"atin%/ali%nment operations )edu"e lo"atin%/ali%nment operations

manual/time "onsumin% manual/time "onsumin%

)edu"e lo"atin%/ali%nment operations )edu"e lo"atin%/ali%nment operations

manual/time "onsumin% manual/time "onsumin%

http://www!hfmg$!org/rouge/tour!aspH

Assemble rom Assemble rom

TopTop

Assemble rom Assemble rom

TopTop

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Thank you for your attentionThank you for your attention

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Mech 424 Lecture 72007