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Visit to Nipp ond enso, July 29-30, 19911

Background

Ou r hosts for this visit were Mr. Fukaya, General Mana ger of the Produ ction

Engineering Depar tm ent, Mr Tsuchiya, Fuk aya's R&D Manager, a youngengineer Mr H arad a, and at d inner Mr Ito, the Execut ive Managing Director

of Production Engineering.

Nipp ond enso Co Ltd. is a form er subsidiary of Toyota Motor Co. that m akes a

w ide variety of autom otive comp onents, such as alternators, motors and

actuators, air cond itioning systems, engine components and controls,

rad iators, dash board displays, brake control systems, and so on. It has

man ufacturing plants worldw ide to satisfy man y automotive manu facturers.

H and ling the w ide diversity of produ ct models and respond ing to the Just in

Time ord ering system p hilosoph y have heavily affected h ow N ippon den so

designs and man ufactures produ cts.

Nipp ond enso is a high technology comp any. Basic and ap plied research cover

materials, vacuum app aratus, semicond uctor fabrication m ethods, ceramics,

robotics, vision systems, factory au toma tion software, simu lation systems for

testing d river reactions, and CAD/ CAM. Major d esign th rusts over the p ast 10

to 15 years includ e "ma naging d iversity," designing n ew p rod ucts faster,

overlapp ing design tasks wh ile man aging risk, and dram atically redu cing the

size and w eight of pr odu cts while increasing qu ality and perform ance.

The company h as 41000 emp loyees. Of these, abou t 5000 are d esign engin eers,

1500 are pr od uction engin eers. At the new R&D center w here th e visit tookplace there are currently 150 researchers. A major characteristic of

N ippon denso , which I have noted in man y previous reports dating back to

1977, is that it makes mu ch of its own au tomation equip ment a nd nearly all

of its 3500 robots. This com mitm ent to m anu factu ring equ ipm ent excellence

is one pa rt of its comm itment to man ufacturing excellence in gen eral.

The typical working year at N ipp ond enso and in Japa n generally is 2200

hou rs, comp ared w ith 1800 in the US. The governm ent is trying to get th is

red uced to 2000 by 1994 and 1800 by 1996. Each Japanese comp any is

attemp ting to reach this target, facing var ious problem s.

1 I p u b l is h e d a p a p e r o n t h i s co m p a n y t h a t c o n t a i n s in f o r m a t io n fr o m t h i s v is it

a n d o t h e r s g o in g b a c k m a n y y e a r s : " Ni p p o n d e n s o Co . Lt d . , A Ca s e St u d y o f

St r a t e g i c Pr o d u c t D e s ig n , " R e s e a r c h i n En g i n e e r i n g D e s i g n , (1 9 9 3 ) vo l 5 , p p 1 2

20 .

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Nipp ond enso characterizes its pr odu cts as follows:

Quality first

Wide range of prod uct variety

High speed mass production

Mixed p rodu ction (several varieties in one p lace) Just in Time produ ction m ethod

OEM sales mainly

These conflicting characteristics (especially variety, mass production, and

mixed pr odu ction) have driven the comp any into a variety of design and

autom ation method s. These are covered below.

Automation an d Produ ct Developm ent Techn iques

An imp ortant feature of Nipp ondenso is an obvious long term enterprise-

w ide strategy for how to grow the company into a m aster of manu facturingproducts with these characteristics. Nippondenso has evolved a systematic

app roach to m anaging d esign p rocesses, designing carefully to sup port JIT

operations, and developing larger and larger systems of automation. In the

1950's they had "spot " au tom ation (wh at we wou ld call islands); in the 60's

they h ad lines; in the 70's "areas," mean ing p resum ably several lines of the

sam e typ e or severa l lines conn ected; in th e 80's and early 90's "cube" or

"totality." Such increasing au toma tion creates serious dan gers for a comp any

w hose customers sw itch sp ecifications, alter m odel p rodu ction v olumes,

dem and instant response to ord ers, and increase variety of produ cts.

Nipp ondenso has only gradu ally realized how deep the dan gers can be andhas instituted several procedu res for combatting th em. These includ e

simu ltaneou s prod uct-process developm ent, a classification of levels of

necessary flexibility in pr odu ction, and a classification of degree of inn ovation

in d esign pr ojects.

Classifying Flexibility

N ipp ond enso's classifications are as follows:

Flexibility for Prod uct Variation - configuration, size, mod el, and typ e are

levels of variability within the p rod uct itself that are increasingly d ifficult forthe autom ation system to accommod ate

Flexibility to Design Ch ange - m inor chang es are often easy to accomm od ate,

mod el changes are hard er, and the next generation of the produ ct usually

requires a new factory

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Flexibility to Prod uction Volum e Chan ge - total volum e fluctuation requires

reassigning man ufacturing systems to d ifferent prod ucts; grad ually increasing

volume n ormally requires buying m ore capacity; fluctuations amon g pr odu ct

types requ ire reassigning prod uction capability between the types.

In response to th ese needs, Nipp ond enso has u tilized several strategies,beginnin g in the 1960's: (See Exhibit 1)

FMS-0 - Use specialized autom ation with n o flexibility and mak e rigidly

stand ard ized p rod ucts; an examp le is little control relays - Mr Fukaya n otes

that strong efforts at standard ization occur even w hen au tomation at levels 1,

2, and 3 below are adop ted. Furtherm ore, FMS -0 is the preferred ap pr oach

and is used w herever possible.

FMS-1 - Design the p rod uct w ith several versions of each p art, capab le of

being intermixed: 3 fronts, 4 midd les, 3 backs, total 36 typ es; an exam ple is a

pan el meter gage, in w hich m any var ieties of one basic model are m ademinu te by minute based on a stream of ord ers from Toyota [Nevins and

Whitney]

FMS-2 - Design the pr odu ct with a common outer shell and interchangeable

interiors, and p rovide robots and sensors as needed to make qu ick changes

from one to an other; several mod els of an air cond itioner are m ade th is way,

all being essentially the sam e size

FMS-3 - Design prod uct and process so intimately that one can even change

the outside shell's length and d iameter withou t affecting the autom ation

system . The Type III altern ator (see below) is an examp le.

Flexibility m eans not only the ability to switch som e imp ortan t factors of the

prod uct but to switch rap idly. Nipp ondenso has w orked over the decades to

cut the changeover time from h our s to minutes to second s, w hile at the same

time in creasing the rang e of flexibility.

The size of the prod uct is one of the m ost important factors in the d esign of

an au tomation system. Sup porting a later change in pr odu ct size without

rebu ild ing the system is almost im possible. Yet as cars become smaller and

lighter, so mu st their compon ents. Only the largest cars can take th e largest

compon ents; even here, however, the m anu factur ers are pressing for smallercompon ents wh ich perform m ore fun ctions. One can no longer simply

red uce the capability of the prod uct for use in a smaller car w hile keeping th e

outer shell the same. The shell must shrink, too. As m ore varieties of cars are

mad e, more sizes of the same p rodu ct are needed , each m ade in smaller

prod uction volum es than before. Lower p rodu ction volumes mean less

efficient au tomation u nless some w ay can be found to make all sizes on one

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autom ation system. Thus FMS-3 is a very difficult bu t imp ortant level to

achieve.

Sum marizing, the u ltimate factory can m ake any qu antity of any item

w ithout any penalty for switching. The d isadvantage of curr ent autom ation

systems is that they ar e too focussed on a small range of mod els of onepr odu ct. If d eman d for one version of alternat or, say, rises w hile that for

another falls, the und erloaded line cann ot help the overloaded one. Instead,

one mu st build more lines, resulting in overcapacity and w asted investment.

Several generic appr oaches exist to this long-stand ing p roblem: pred ict futu re

dem and perfectly, make sup er-intelligent m anu facturing systems that can

switch, or d esign th e prod ucts and their manu facturing processes to contain a

measure of alterability. I call the latter "smar t pr od ucts" below. It is probably

the best of the thr ee app roaches, the first being obviously un available and the

second beyond the current state of the art except in restricted but v ery useful

situations. Nipp ondenso has adopted th e smart pr odu cts approach andshow ed som e interesting examples.

Classification of N ew Product Developm ent Efforts

This classification is as follow s:

1. Inn ovative, totally new pr odu ct (10% of d esign efforts); examp les includ e

active susp ension or CRT dashboard displays

2. Strategic new product (called Jikigata); these are major, market-share-

grabbing imp rovemen ts of existing prod ucts such as radiators, alternators,and fuel pum ps

3. Semi-new p rod ucts; these are in fact minor imp rovemen ts in performan ce

of existing items; several such improvements come along between Jikigata's

The bulk of the visit focussed on the Jikigata for a new alternator .

The Jikigata Process

Jikigata efforts are d irected at prod ucts wh ich are m ainstays of the comp any,

feed a mass prod uction requirement for a pop ular car, and face importantcompetition, thus requ iring strong innovation. On top of this, such prod ucts

require timely and reliable delivery. These requirements have forced the

creation of new d esign staff organ izations and close involvem ent of top

man agement. While CAD and CAE have played imp ortant sup porting roles,

the most imp ortant element of such developm ents is creation of new

man ufacturing m ethod s to sup port the "smar t" flexible design. This has

meant m aking prod uction engineering an equal partner in the design process.

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N ippon d enso , like many Japanese comp anies, maintains Prod uction

Engineering as a corp orate level activity with a Director (equ ivalent to

Executive VP) as its head . Thu s the comp any w as long prep ared for the

required organizational changes.

It is imp ortant to realize that th is is a more soph isticated activity than mere"d esign for man ufacture" or "design for assembly." A new level of

autom ation/ flexibility is being sought, and it cannot be achieved u nless new

man ufacturing method s are created, method s which are enabled, not just

eased, by the prod uct design itself.

A Jikigata effort combines corp orate prod uction engineering and a pr odu ct

d ivision's capabilities as follows:

Corporate Prod uction Engineering Product Group

System Section Planning CenterProcessing Section Product Engineer

Materials Section Manufactu ring Department

Machinery and Tools Department Quality Assurance

Produ ct d evelopm ent begins after a laun ch d ecision by the N ew Produ ct

Developm ent Council, which app oints a prod uct developm ent team (4 - 5

engineers) and a pr ocess d evelopm ent team (2 - 3 engineers). These teams

work together to create the concept design sp ecs. Each then sp lits into separate

activities, enlarges to about 20 members each, and comes u p w ith an action

plan to m eet the spec. Once the plan is app roved it is cond ensed to a single

sheet of pap er and given to everyon e. These 40 - 50 engineers stay w ith the

pr od uct u ntil the end of the project, later being joined by abou t 100

man ufacturing equipm ent d esigners. The m ost specialized one third of the

machines (by cost) are mad e in-house, while the more ord inary ones are bu ilt

by contractors.

The plan (Exhibit 2) mu st be challenging bu t reasonab le. It mu st contain the

total view an d p lenty of detail. It involves top man agement, wh o attend

mon thly follow-up meetings. Each goal has a responsible person an d a list of

risk-managem ent actions. Each goal is classified as to its impor tance to the

pr oject an d its level of risk. The imp ortance levels range from "M" (for mu st

hav e) to "W1" (wan t very m uch) to "W2" (wan t, but n ot so mu ch). Risk

varies from "A" (feasible tod ay) to "B" (curren tly being stud ied for ap plication

to ma ss prod uction) to "C" (und er basic examination, not ou t of the lab yet).

At each p oint in th e schedu le there is a "T" (target) date after w hich, if a risky

process or design element h as not been achieved, one of the p rearranged

alternates will automa tically be substituted .

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On top of all this, Nip pon den so aimed a t redu cing the developm ent time

from the customary 6 years to 4, by overlapp ing prod uct and process

d evelopm ent activities. For th e Type III alternator the d evelopment time

app arently was 5 years.

Along with th is elaborate planning pr ocess, N ippon den so has some "usefultools." These comp rise the usu al CAD/ CAM/ CAE software, plus value

engineering, group technology, and variation redu ction, plu s N ippon den so's

own design for assembly evaluation method , a variety of system engineering

aids like discrete event simu lation and p rocess FMEA, and q ua lity

man agement m ethods (design reviews, QC techniqu es, and the Taguchi

meth od). Calling th ese "useful tools" reveals N ippon den so's priorities: get

the m ethodology in p lace first, then sup port it with tools.

All of the d ebates and trad eoffs involved in these efforts are carried ou t by

experienced p eople. When there is a major pr oblem a top execut ive decides.

Design is vulnera ble to change, often forced by th e actions of a comp etitor. Inalternators and air cond itioners, wh ere Nippon den so dominates,

comp etitors' actions are less disru ptive of the design schedu le, bu t in brake

systems where Nipp ond enso does not dom inate, the sched ule is more

vu lnerable. The availability of top m anagem ent and their w illingn ess to take

the resp onsibility and mak e d ecisions qu ickly is cru cial. In th is sense,

N ippon denso is like Nissan and other comp anies who organize to absorb

change du ring the d esign p rocess rather than tr y to resist it.

N ote, too, that Nipp ond enso is willing to u se the overlapp ing tasks method

even on pr ojects w ith lots of technical risk. Overlapp ing bring s the risk of

more change, but N ippond enso and Nissan both feel that changes forced byout side pr essures su ch as comp etitors' actions are mor e severe. This fact

slightly counters Prof Kimura's feeling that only "understood" processes and

prod ucts could be ap proached th is way. Mr Fukaya w as quite clear on this

point, and said that Concurrent Engineering (joint operation of produ ct and

process design teams with m onthly follow-up by top m anagement) was the

w ay to accomp lish it. They all agree that it is based on hu ma n

commu nication and experience, and w ish for comp uterized versions of CE. I

did not hear them su ggest any ways to create them.

N ippon denso's prod uction engineering people are also sympath etic to the

idea that comp uter aids w ill help this pr ocess and fervently wish for suchhelp, but th ey do not see it becoming available soon and do n ot think it w ill

be a dom inant featur e of their success. Yet they are d eveloping several

effective compu ter tools and see w here other s might be introd uced . See below

for a summ ary of these.

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Develop men t of the Type III Alternator

The main compon ents of an alternator are the stator, the rotor, the tw o-piece

cast outer case, and the rectifier assembly. The goals of the redesign w ere to

prod uce an alternator that could be mad e in several lengths and diameters on

the same fabrication and assembly equipm ent. Imp ortant changes in thed esign of all four comp onent s were requ ired. Some w ere relatively easy, such

as cutting d ifferent d iameter grooves on d ifferent size cases. Redesign to

per mit assem bly from one d irection w as also not too difficult to achieve.

Others requ ired considerable innovation, such as making d ifferent d iameter

stators. This was d one by coiling stator laminations stamp ed from long strips

of steel (Exhibit 3) rather th an stam ping rings from steel sheets and stacking

them up . (The amou nt of scrap ma terial is also drastically cut this w ay.) The

w ire wind ings for the stator are formed sep arately from th e stator itself and

pu shed rad ially outward into the grooves in the stator rather than being

w ound in place in the stators. Changing the d iameter of the w indings is easier

this way. Most of the size changes can be mad e almost w ithout stop ping th emanufacturing equipment.

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Cont inuous Measurement

of Mat erial Thickness

Cont inuous

Exhibit 3. High Speed Coiling of Stator Cores in Three Diamat ers and Several

Stack Heights

Altogether 74 new m anu facturing technologies were d eveloped . This p roject

occurred in the early 1980's.

The resulting d esign comes in th ree main sizes w ith capacities ranging from

35 to 80 amp s. Within each size there ar e abou t 250 variations.

These alternators are assembled on autom ated assembly lines that use m ostly

specialized au tomation for the assembly m oves themselves plus robots to

feed th e par ts from trays to the assemb ly stations. A few simple fixture

changes, accomp lished m anually, sup port changes in pr odu ct model.N ipp ond enso bu ilt these lines in 1987 after seeing a film in 1980 mad e in 1977

by our grou p at Drap er dem onstrating complete robot assembly of Ford

alternators.

The spirit of these innovations can also be seen in the w ay N ippon den so

redesigned r adiators a few years earlier. [Ohta an d H anai] A major feature w as

ma chines that could switch sizes of compon ents in a few seconds, plu s a snap -

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together assembly method that eliminated the n eed for fixtures in the

d ifferent sizes. The cost of the fixtu res wa s saved bu t mor e imp ortant ly the

time requ ired to sw itch from on e size set of fixtures to anoth er was

eliminated . Some of these techniques w ere pioneered by General Motors

H arrison Radiator Division bu t not pu t in place as comp letely as at

Nippondenso .

Radiators and alternators are clear examp les of "smar t pr odu cts," being

d esigned so that the challenging man ufacturing strategy of conqu ering variety

could be achieved w ithout basic advan ces in man ufacturing kn owledge.

Innovative manu facturing methods w ere ind eed mad e, however. Deciding

how to partition the p roblem into prod uct innovation and process

innovation clearly required a single team w orking together from the start of

the p roject. Success would have been u nlikely if pr ocess engineers had

merely critiqued the prod uct engineers' design, and w ould h ave been

impossible if the process equipm ent had been merely pu rchased from

vendors after produ ct design w as comp lete.

Use of Compu ters in the D esign Process

Nipp ondenso has a large CAD/ CAM/ CAE activity, combining their own

softw are developm ent and use of comm ercial softwar e. The system they hav e

d eveloped is similar to several comm ercially available "framew orks" in th e

sense that it sup ports m any ap plication program s as long as they respect

certain data conversion p rotocols, but there is no true comm on d ata base. In

ad dition to this core system, there is the typical array of CAE plus a ran ge of

software that sup ports prod uction prep aration and prod uction control.

The goals of CAD/ CAM/ CAE are stated as

imp roving the efficiency of prod uct d evelopm ent

shortening the lead time for new prod ucts

making it easier to design prod uct variants

helping create smaller an d lighter p rodu cts

(Note that N issan denied th at a goal of its CAD w as to shorten the lead

time...) Design is sup ported by NA DAMS ( Nip pon d enso Ad vanced Design

and Manufacturing System), wh ich has been u nd er continuous development

since 1980. It is wr itten in PL-1 with recent ad d itions in C. Outsid e cont ractorsw rote most of it und er the leadership of an internal group of program mers. It

ru ns on IBM 3090's and su pp orts about 1000 term inals. N ADAMS sup por ts

2D and 3D wireframe m odels, surface freeform shap es using Coons su rfaces

and rational B-splines, and solid models.

All items d esigned in N ADAMS are in one d atabase accessible to the

designers, including th ose who d esign p rodu ction equipment. Casting and

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molding d ies, NC machine operations, robot program ming, operating mod els

of parts and prod ucts, and simu lations are examp le applications sup ported.

There is an expert system to help d evise cutting process plans, typical CAE for

vibration, stress and th ermal analyses, mold flow simulations to aid d ie

d esign, and some fault tolerance analysis software that w as not explained

further.

For examp le, the mold flow p rogram (IMAP, developed by Toyota Central

R&D Laboratories, Inc.) helped N ipp ond enso red uce the w eight of its air

conditioner case and avoid h aving a hole develop d uring m olding. The

nu mber of actual prototyp es needed w as redu ced by 66%.

The metal cutting expert system is based on Metcut's data plu s 650 rules

provid ed by N ippond enso's process engineers. The rules comp rise knowledge

abou t how to process certain geometries plu s form ulas for calculating

feed rates and tool wear, for exam ple. The software chooses tool material and

size, cut dep th, feedrate, cutting speed, an d cutter rotation rate. In a side-by-side test, process engineers pr ovided process plans for a p recision su rface that

varied by 4 to 1 in recomm ended cutting speed . Only one engineer

recommen ded a cutting sp eed as high as the expert system did. This cutting

speed was verified in a test. The system th us h as the capability to solve three

pr oblems: lack of experienced p rocess plan ners, non-u niformity of their

plan s, and un w illingness of plan ners to choose aggressive plans, thu s costing

time and m oney un necessarily.

Tou r of CAE Facility

The facility I toured was a training center. It contains a w ide var iety ofw orkstations bu t m ostly IBM 5080's. I saw tw o d emon strations: robot offline

programming and supercompu ter output showing FEM studies.

Robot offline program ming is sup ported by a w ireframe 3D modeler that

perm its a user to build u p a mod el of a w orkstation from basic shapes. A

primar y function of the program is to predict and im prove th e cycle time of

the robot workstation. The comp uter already has m odels of Nip pon denso's

various robots (which it makes in-hou se). I could not find ou t how the

coordinate d ata were pu t in so that workp ieces, fixtures, and teach p oints for

the robot could be described. Collision avoidance is done by trial and error,

u sing the mod eler's intersection cap ability. Straight line pat hs are comp utedau tomat ically as a first try an d th e user m odifies them to avoid obstacles or

imp rove cycle time.

Several FEM examp les were av ailable. These includ e fluid flow in p lastic

injection mold ing, turbu lent mixing an d heat tran sfer inside the air

conditioner betw een cold an d h ot air, stress-strain, and flow inside a fuel

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man ifold. NADAMS supp orts pre-and post-processing, and a commercial

FEM pa ckage does the calculations on the m ainfram e.

Developments in Assembly Techn ology

Two interesting activities of the Assembly R&D grou p w ere presented by MrHarad a and Mr Sugito: Design for Assembly, and Assembly Technology. The

Assembly R&D grou p h as only 5 mem bers and was begun in 1985. Its jobs

includ e interacting with the research commu nity at home and overseas,

developing ways to simp lify produ cts using their own DFA methodology, and

d eveloping ways to assemble difficult p rod ucts that can't be simplified.

Assembly Technology is divid ed into tw o para llel efforts: dexterous/ intricate

assembly an d large variation assem bly of simp le items. (Exhibit 4)

Engineering inn ovation is used on the first kind w hile economic app roaches

are u sed on the second because th ey are already technically easy but too costly

to automate.

For large variation p rod ucts, an econom ic analysis showed that cost of

prep aring and feeding parts grow s mu ch faster than other costs as the nu mber

of variations grow s. Efforts are going into var ious "low cost" feeding an d

prep aration method s, includ ing an attempt at low cost bin picking. Bin

picking is being u sed in only one factory app lication, however. Other

app lications are u nd er d evelopm ent. Reconfigurable grippers and pallets are

also und er consideration, along w ith such app roaches as molding grou ps of

parts on to one backbone and cutting th em off at the moment of assembly.

For technologically challenging assembly tasks, such as fitting un wieldy ,flexible, and warp ed items together, Nipp ondenso long ago conclud ed that

"intelligent, dexterous, and ad apt able" robots were too expen sive or

un available. Instead, th ey d ecided to "utilize the char acteristics of the

pr odu ct" as well as to redesign the p rodu ct so that assembly could be

accomp lished. This is another example of the "smart prod uct" app roach.

A fine example show n w as fitting top an d bottom halves of molded p lastic air

conditioner h ousings togeth er. (Exhibit 5) These fit by tongu e and groove

arou nd a large perim eter ("island "). Since the cases war p, the ha lves cann ot

just be push ed together . Fixtu ring cou ld be used to force the halves in to th e

correct shape but that w ould require costly fixtures and/ or making the partstoo flimsy.

The problem gets w orse wh en the joint has a gap ("discontinu ity") or two

rather th an covering the entire perimeter. The w orst situation occurs w hen

there are "intermediate parts" such as pivoted d amp er doors w here one end

of the hinge pin fits in a hole in one case half and the other en d fits in a hole

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in the other h alf. Such d oors are placed up right in the lower h alf but flop

over to one side and the hinge pin w ill not line up with th e up per h alf's hole.

People cur rently assemble these par ts. They pu sh and bang th e case halves

together, reaching inside to line u p th e dam per h inge pins and the case holes.

It is an obvious bottleneck on the p rod uction line an d inherently difficult toautomate.

The robot solutions have been dem onstrated in the lab but not app lied in the

factory. They are elegant and involve a mix of robot angu lar man euvering of

the top p art, redesign of tongue and groove shapes, and redesign of dam per

d oors. This is the app roach I called "smart p rod uct" above.

To fit a tongu e-groove that covers the ent ire perim eter, the robot tilts the top

half and m ates the parts on one side. It then p ivots the top h alf dow n gently

by hinging at the initial contact point, and the tongu e rolls into the groove.

When th e joint has a gap, the above method is used, starting at a p ivot point

opp osite the gap and rolling around so that the parts are mated at one end of

the gap . A vision system is then u sed to find the top in relation to the bottom

at the other end of the gap, and the robot pushes and slightly d eforms the top

half until the parts are aligned. Then the pivot-roll method is used to m ate

the parts w hile not d isturbing the m ate achieved at the first end of the gap.

When there ar e several gap s, the one in the m ost flexible region of the case is

ma ted first, then the n ext most flexible, and so on.

When there is one dam per d oor, the robot pushes it upright with the top half

of the case and catches the d oor hing e in the hole in the case. Then it repeatsthe tongu e-groove method . The hinge pins on the dam per are mad e extra

long so that they do not fall out du ring the pivoting operation. When there

are several doors, this process is repeated for each door, and the hinge p in of

each d oor is designed to be longer than that of the next d oor so that the

sequence of door m ates can be controlled.

Whether this scheme can be app lied reliably and at high enough speed in the

factory is unclear at this time but given N ipp ond enso's past record, it will be.

It is a pretty sop histicated app roach and represents "design for assembly" as

high art.

Nipp ondenso has also developed its own DFA evaluation method.

Nipp ond enso s method is broader and more sophisticated than typical DFA

method ologies, wh ich m ost people agree focus too m uch on small parts. It

contains 65 points of evaluation, such as how parts m ust be p repared for

feeding, how m any variations there are in p arts and p rodu ct, whether a p art's

feeding m ethod sup ports variety, how difficult the assembly technique mu st

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be, and how man y parts there are (the most imp ortant item). Produ ction

engineers perform th e evaluations and give advice to the prod uct designers.

An in teresting red esign activity is called Variation Redu ction. Its aim is to

red uce the effect of multiple mod els on the assembly processes. Method s used

includ e mod ularizing the prod uct into fixed p ortions and variable portions,supp ressing minor variations and using more common parts instead, and

using the FMS-1 technique. This top ic is a su bject of ongoing research an d Mr

H arada is gathering more examples from arou nd the comp any.

Twice a year they h old a DFA seminar to tra de stories, hear adv ice from both

prod uct engineers and p rocess engineers, and teach the method. Mr H arada's

goal is to create a DFA progra m based on a solid m odeler that w ill help

prod uct d esigners evaluate their own designs. Other comp anies I have asked

about su ch an app roach (a subject of my own research) say that they do n ot

believe prod uct designers will ever have the time or kn owledge to d o such

evaluations themselves. Mr H arada will move to N ippond enso TechnicalCenter USA, Inc. near Detroit and w ill survey r esearch opp ortun ities from

there.

Prof Kimu ra noted later that both Boothroyd/ Dewhu rst and Draper

Laboratory research on d esign for assembly and simplification of prod ucts

have had a strong influence in Japan . The B/ D method is very pop ular

although its limitations are recognized.

Reference

[Nevins and Whitney] J L Nevins and D E Whitney, eds, Concurrent Designof Products and Processes, New York: McGraw-Hill, 1989, pp 54-58.

[Ohta and Hanai] K. Ohta and M. Han ai, "Flexible Autom ated Prod uction

System for Automotive Radiators," 1st Japan-USA Symposium on Flexible

Au tom at ion , Osaka, Japan , 1986, Kyoto: Japan Assoc of Autom atic Control

Engineer s, pp 553-558.