Design for Manufacturing and Assembly.ppt

7/21/2019 Design for Manufacturing and Assembly.ppt

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Ken Youssefi UC Berkele 1

Design for Manufacturing and Assembly

Design for manufacturing (DFM) is design based on

minimiing t!e cost of "roduction and#or time to market

for a "roduct$ %!ile maintaining an a""ro"riate le&el of

'uality !e strategy in DFM in&ol&es minimiing t!e

number of "arts in a "roduct and selecting t!e a""ro"riate

manufacturing "rocess

Design For *ssembly (DF*) in&ol&es making attac!ment

directions and met!ods sim"ler


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Ken Youssefi UC Berkele +

DFM and DFA Benefits

,t reduces "art count t!ereby reducing cost ,f a

design is easier to "roduce and assemble$ it canbe done in less time$ so it is less e-"ensi&eDesign for manufacturing and assembly s!ould

be used for t!at reason if no ot!er

,t increases reliability$ because if t!e "roduction

"rocess is sim"lified$ t!en t!ere is less

o""ortunity for errors

,t generally increases t!e 'uality of t!e "roduct for t!e

same reason as %!y it increases t!e reliability


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Ken Youssefi UC Berkele .

DFM and DFA

DFM and DF* starts %it! t!e formation of t!e

design team %!ic! tends to be multi/disci"linary$including engineers$ manufacturing managers$

cost accountants$ and marketing and sales

"rofessionals

!e most basic a""roac! to design for

manufacturing and assembly is to a""ly design

guidelines

You s!ould use design guidelines %it! anunderstanding of design goals Make sure t!at t!e

a""lication of a guideline im"ro&es t!e design

conce"t on t!ose goal


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DFM and DFA Design Guidelines

Minimie "art count by incor"orating multi"le functions into

single "arts e&eral "arts could be fabricated by using different

manufacturing "rocesses (s!eet metal forming$ in2ectionmolding) *sk yourself if a "art function can be "erformed by a

neig!boring "art


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Modularie multi"le "arts into single sub/assemblies


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Design to allo% assembly in o"en s"aces$ not

confined s"aces Do not bury im"ortant com"onents


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6arts s!ould easily indicate orientation for insertion

6arts s!ould !a&e self/locking features so t!at t!e

"recise alignment during assembly is not re'uired 7r$

"ro&ide marks (indentation) to make orientation

easier




tandardie "arts to reduce &ariety




Design "arts so t!ey do not tangle or stick to eac!

ot!er


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Distinguis! different "arts t!at are s!a"edsimilarly by non/geometric means$ suc! as color

coding




Design "arts to "re&ent nesting ;esting is %!en

"arts are stacked on to" of one anot!er clam" to

one anot!er$ for e-am"le$ cu"s and coffee lids


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Design "arts %it! orienting features to make

alignment easier


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6ro&ide alignment features on t!e assembly

so "arts are easily oriented




Design t!e mating "arts for easy insertion 6ro&ide

allo%ance on eac! "art to com"ensate for &ariationin "art dimensions




Design t!e first "art large and %ide to be stable and

t!en assemble t!e smaller "arts on to" of itse'uentially

,nsertion from t!e to"

is "referred




,f you cannot assemble "arts from t!e to" do%n

e-clusi&ely$ t!en minimie t!e number of insertiondirection ;e&er re'uire t!e assembly to be turnedo&er



Minimizing the Number of Partso determine %!et!er it is "ossible to combine neig!boring

"arts$ ask yourself t!e follo%ing 'uestions=

If the answer to all questions is NO,you should

find a way to combine the parts.

Must t!e "arts mo&e relati&e to eac! ot!er>

Must t!e "arts be electrically or t!ermally

insulated>

Must t!e "arts be made of different material> Does combing t!e "arts interfere %it!

assembly of ot!er "arts>

?ill ser&icing be ad&ersely affected>


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Minimizing the Number of Parts

!e conce"t of t!e theoretical minimum number of parts

%as originally "ro"osed by Boot!royd (198+)During t!e assembly of t!e "roduct$ generally a "art

is re'uired only %!en@

1. A kinematic motion of the part is required.

. A different material is required.

!. Assembly of other parts would otherwise be

pre"ented.

,f non of t!ese statements are true$ t!en t!e "art is notneeded to be a se"arate entity

KISS Keep It Simple Stupid


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DFM Design Guidelines

*not!er as"ect of design for manufacturing is to make

eac! "art easy to "roduce

!e u" to date DFM guidelines for different "rocesses

s!ould be obtained from "roduction engineerkno%ledgeable about t!e "rocess !e manufacturing

"rocesses are constantly refined

DFM D i G id li


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Ine!tion Molding

In#ection $oldin%

Fabri!ation of Plasti!s


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Ine!tion Molding

Minimie section t!ickness$cooling time is "ro"ortional to

t!e s'uare of t!e t!ickness$

reduce cost by reducing t!e

cooling time

6ro&ide ade'uate draftangle for easier mold

remo&al




Ine!tion Molding

*&oid s!ar" corners$ t!ey

"roduce !ig! stress and

obstruct material flo%

Kee" rib t!ickness less t!an

4:A of t!e "art t!ickness in

order to "re&ent &oids andsinks




Ine!tion Molding

6ro&ide smoot! transition$

a&oid c!anges in t!ickness

%!en "ossible

Kee" section t!ickness uniform

around bosses




Ine!tion Molding

Use standard general tolerances$ do not tolerance@Dimension olerance Dimension olerance

: d +3 :3 mm : d 1: ::+ inc!

+3 d 1+3 :8 mm 1 d 3: ::. inc!

1+3 d .:: 1: mm 3 d 1+: ::0 inc!

.:: 13 mm 1+: ::3 inc!

tandard t!ickness

&ariation

Minimum t!ickness recommended@

:+3 inc! or 43 mm$ u" to 1+3 for large

"arts

ound interior and e-terior corners to

:1/:13 in radius (min)$ "re&ents an

edge from c!i""ing




"otational Molding

* "redetermined amount of "lastic$ "o%der or li'uid form$

is de"osited in one !alf of a mold

!e mold is closed

!e mold is rotated bia-ially inside an o&en

!e "lastics melts and forms a coating o&er t!e inside

surface of t!e mold

!e mold is remo&ed from t!e o&en and cooled

!e "art is remo&ed from t!e mold

otational molding "rocess consists of si- ste"s

" i l M ldi M hi


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Ken Youssefi UC Berkele +8

"otational Molding Ma!hines

ock and roll mac!ine

Eertical %!eel mac!ine

!uttle mac!ine

urret mac!ine


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Ken Youssefi UC Berkele +9

"otational Molding

Ad"anta%es

Molds are relati&ely ine-"ensi&e

otational molding mac!ines are muc! less

e-"ensi&e t!an ot!er ty"e of "lastic "rocessing

e'ui"ment

Different "arts can be molded at t!e same time

Eery large !ollo% "arts can be made

6arts are stress free

Eery little scra" is "roduced


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Ken Youssefi UC Berkele .:

"otational Molding

&imitations

Can not make "arts %it! tig!t tolerance

arge flat surfaces are difficult to ac!ie&e

Molding cycles are long (1:/+: min)

$aterials

6olyet!ylene (most common)$ 6olycarbonate (!ig! !eat

resistance and good im"act strengt!)$ ;ylon (good %ear

and abrasion resistance$ good c!emical resistance$ good

toug!ness and stiffness)


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Ken Youssefi UC Berkele .1

"otational Molding

6olycarbonate %all t!ickness is ty"ically

bet%een :4 to .53 inc!es$ 1+3 inc! being an

ideal t!ickness 6olyet!ylene %all t!ickness is in t!e range of 1+3

to +3 inc!$ u" to 1 inc! t!ick %all is "ossible

;ylon %all t!ickness is in t!e range of :4 to 53inc!

Nominal wall thickness

" i l M ldi # l


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Ken Youssefi UC Berkele .+

"otational Molding #$amples

" t ti l M ldi # l


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Ken Youssefi UC Berkele ..

"otational Molding #$amples

DFM D i G id li


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Sheet%metal Forming


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DFM Design Guidelines &asting


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DFM Design Guidelines % &asting

Casting$ one of t!e oldest manufacturing "rocesses$ dates

back to 0::: BC %!en co""er arro%!eads %ere made

'astin% processes basically in"ol"e the introduction of a

molten metal into a mold ca"ity, where upon

solidification, the metal takes on the shape of the mold

ca"ity.

im"le and com"licated s!a"es can be made fromany metal t!at can be melted

G-am"le of cast "arts= frames$ structural "arts$

mac!ine com"onents$ engine blocks$ &al&es$ "i"es$

statues$ ornamental artifactsH

Casting sies range form fe% mm (teet! of a i""er)

to 1: m ("ro"ellers of ocean liners)


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&asting Pro!esses

1 6re"aring a mold ca&ity of t!e desired s!a"e %it!

"ro"er allo%ance for s!rinkage

+ Melting t!e metal %it! acce"table 'uality and tem"

. 6ouring t!e metal into t!e ca&ity and "ro&iding

means for t!e esca"e of air or gases

0 olidification "rocess$ must be "ro"erly designedand controlled to a&oid defects

3 Mold remo&al4 Finis!ing$ cleaning and ins"ection o"erations

Sand &asting 'erminolog(


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Sand &asting 'erminolog(


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Ken Youssefi UC Berkele 0:

&asting Defe!ts

(ot spotsI t!ick sections cool slo%er t!an ot!er sections

causing abnormal s!rinkage Defects suc! as &oids$ cracks

and "orosity are created


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&asting Defe!ts and Design &onsideration

DFM D i G id li & ti


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Ken Youssefi UC Berkele 0+


ecommended minimum section t!ickness


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Ken Youssefi UC Berkele 0.



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DFM Design Guidelines Ma!hining

Documents

Design for Manufacturing and Assembly.ppt