21COE, University of Tokyo

MMRC Discussion Paper No. 202

MMRC
DISCUSSION PAPER SERIES

MMRC-F-202

Design and Manufacturing of Car Doors:
Report on Visits Made to US, European andJapanese Car Manufacturers in 2007
Daniel E. Whitney
MIT Engineering Systems DivisionCambridge MA
March 2008

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Design and Manufacturing of Car Doors: Report on Visits Made to US, European andJapanese Car Manufacturers in 2007
Daniel E. Whitney
MIT Engineering Systems DivisionCambridge MA
Everyone designs and manufactures doors differently and everyone thinks their way is thebest.

I. BackgroundStarting in 2003, a research project was initiated at MIT aimed at understanding how to
improve the design process for car doors. This research approached doors as complex
systems in their own right and sought to make recommendations on how to improve door
design in a systematic way. The results of this work, documented in [Stevens] and[Noor], are discussed in a later section of this report. 1
In 2007 the author, funded by the International Motor Vehicle Program (IMVP), visited
Europe and Japan and studied door design and manufacture by several major auto
manufacturers. The findings from these visits are also discussed later in this report.
The statement at the top of this page reflects the main finding. It contrasts the author’s
finding regarding automobile engines, which are largely designed and manufactured insimilar ways [Peschard and Whitney]. In the discussion section we speculate on why
there seems to be industry convergence in engines but not in doors. 2

II. Characteristics of Doors
Doors are highly complex structures that contain just about everything that a car as awhole contains except for power train elements. Customers interact intimately withdoors and are aware of them along many dimensions, called attributes by Ford andsimilar terms by other companies. Doors also comprise both interior and exterior
elements, causing them to be links between these two domains of the car. Many of theattributes conflict: for example, better water leakage and wind noise behavior will make it
more difficult to close the door; better side intrusion protection will make the door

1

This research project was sponsored by Ford and pursued with consideration given tocomplementing organizational changes at Ford.
2
A study done by Jay Baron of the Center for Automotive Research in Ann Arbor MI in
the late 1990s compared door locator strategies across many car companies and also
found no convergence. Also, no locator strategy could be correlated with the best
variation in door fit [Baron].

2heavier; better leakage around the glass makes it harder to raise the glass, requiringstronger motors, making the door heavier. 3
The main door architectures in use today are shown in Figure 1.

Figure 1. Three Different Door Architectures Used by Companies Visited (courtesyof Jay Baron [Baron])III. Ford Study 2003 - 2007
Ford funded a study of door design under the Ford-MIT Research Alliance. The study
was co-directed by Dr Janice Klein of the MIT Sloan School of Management and Dr
Daniel Whitney of the MIT Engineering Systems Division and Department of
Mechanical Engineering. Both management and technical aspects of door design wereaddressed. The Ford sponsors were Mr Will Boddie, then Vice President of North
American Engineering, and Mr Al Ver, then Vice President of Advanced Manufacturing.
Mr Boddie sought to improve door design by creating a new job title called Closures
System Integrator (CSI) in the Engineering Department and Mr Ver sought similar resultsby creating a new job title called Manufacturing Systems Integrator (MSI). The goal was
to increase focus on door attributes that customers pay attention to, such as wind noise,water leakage, closing effort, and squeaks and rattles, and to coordinate design and
3This list is typical but valuable detail was provided by Mr Olivier Demouy of PSA.

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manufacture of doors to achieve attribute targets with better time to market and lower
variability.
Two strands of research were conducted. In [Stevens], the organizational andmanagement issues were addressed. Engineers and managers were interviewed,
organizational behaviors and power relationships were described, and methods for
improving incentives to accept the CSIs and MSIs and address doors as systems were
proposed. Ford is known for excellence in components, but attention to components hasoften overshadowed the need to compromise among components in order to meet the
attribute targets. Power flows to the components in the form of budgets and signoff
authority, and at best the CSIs rely on reputation and persuasion to obtain thesecompromises.
In [Noor], the design process for doors was documented using the Design Structure
Matrix (DSM) methodology [Eppinger et al]. The DSM has been actively used at Ford
for nearly 10 years and several of the CSIs had learned about it while obtaining advanced
engineering degrees at MIT. DSMs are built by interviewing participants in the process.
Noor also used a second method for documenting the structure of doors as mechanicalassemblies. This method is known as the Datum Flow Chain (DFC) [Whitney]. It allows
engineers to define locator schemes for door parts and necessary assembly tooling so that
achievement of geometric attributes can be documented in a simple and consistent way.
Previous research on DSMs has shown that they are useful for documenting design
processes and showing how components, organizations, and decisions interact. Oncethese are documented for an as-is situation, they can be learned by everyone involved andthe process can be improved by removing redundancies, shortening or eliminating
feedback loops and delays, and improving the accuracy and timeliness of informationexchanges. Previous research on DFCs has shown that they not only document theengineering design intent but also display different organizational ownership of different
parts of the chains. This in turn shows where cooperation and information exchangemust be addressed in order to achieve each geometric attribute.
The DSM developed during this study traced the components and decisions related to
five important attributes and thus does not comprise the entire door design process.
Nevertheless it is large and highly interconnected. These facts show that few decisions
can be made independently from others, and management of interfaces in the door and in
the organization is essential for success. The DSM was also subjected to a time-based
stochastic simulation, which showed that not enough time exists to carefully consider all
the decisions that the CSIs and engineers want to address. As a result, the study
recommended that Ford do more to standardize components, designs, and design
processes, improve Computer-aided Engineering (CAE) methods for predicting door
attributes, and improve design-manufacturing communication. All of these changes will
shorten design time, increase the likelihood that doors will not need engineering changes
after design, and reduce rework loops in the process.

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Both studies recommended maintaining the CSI and MSI job positions and strengthening
the organizational power of those positions vis-à-vis the power of component design
supervisors.

IV.

IMVP Visits 2007

MIT and the IMVP funded a series of visits by Daniel Whitney and IMVP colleagues tocar makers in Japan and Europe in the Spring and Summer of 2007. Additional
information from visits in the US in prior years was added to the more recent visit
findings to fill in gaps. No visit to an engineering office or a plant lasting a day or two
can permit a thorough analysis; even the four year study at Ford uncovered only afraction of the activities, decisions, and effort required to design and manufacture car
doors. Thus the visits must be viewed as snapshots. Every attempt was made to keep
their content consistent so that comparisons would be possible. Each visit focused on
how door attributes are managed during design and manufacture. Particular attention inengineering was paid to job descriptions, organization charts, span of control, state ofstandardization, and design aids such as CAD and CAE. Factory visits covered door
buildup from stamped parts, door mounting to unpainted bodies, door final assembly, anddoor mounting and adjustment during final assembly, with detailed attention paid tolocator schemes.
The companies visited were A, B, C, D, E, and F. We thank our hosts at these companies.

V. Findings
The findings are summarized in Figure 1. In general, the only common thing in theprocesses documented is that all the companies remove the doors after the body is painted,
assemble components to doors on a separate line, and reassemble the doors to the cars
late in the final assembly process. Almost nothing else is common. Each visit looked ata single car’s doors in the factory, and in most cases doors for other cars at the visitedcompany are designed and made differently in many respects. Toyota is notable in its
efforts to design and make the majority of its doors based on the same standards[Whitney et al]. This is due to Toyota’s extensive use of standard components, doorarchitecture, and design and process commonality. Toyota developed its current
standards 5 to 10 years ago. We speculate Toyota’s policy of designing cars for
production anywhere in the world and its practice of making as many as 8 different carson the same line has also spurred the use of standards. The other companies visited havestandardized to lesser degrees, have launched standards practices more recently, or
standardize fewer things. Company E has the least opportunity to standardize because it
makes cars for other car companies and must follow the procedures that their customers
dictate.
In all other matters, designs, design organization, and locator schemes differ widely.
Companies A, B, C and E focus on the door itself from an organizational point of view
and are the most oriented toward the components in terms of design organization and5responsibility. Companies D and F recognize the system nature of doors more explicitly
in the organization of the engineering processes, with D actually having departments andjob titles containing the word “architecture” and “architect.” Toyota addresses the needto integrate by empowering the Production Engineering department [Whitney et al]. As
noted in Section III of this report, Ford introduced the CSI position with the same intent.
Toyota’s focus on production engineering as the integrator is unique in the car industry as
far as we know.
Another important difference among the companies visited regards the scope of design
authority accorded to the closures design organization. At a minimum, such a group has
cognizance over the sheet metal and mechanical items in and on the door. At the
maximum, this group (at company F) is responsible for all the closures and the adjacentglass all around the car. Being responsible for, or owning, all the glass as well as the
sheet metal and mechanical components allows this group to exert coordinated design
cognizance over a number of important attributes.
No one uses the same door architecture although all companies agree that simplicity, lowpart count, and stiffness are marks of a good architecture. Many say they have studied
the others’ architecture and cannot understand why they should switch, being quitesatisfied with their own choices.
Most companies showed me multiple cells in the body shop comprising multiple robots
that accomplish door buildup. These systems contained between 12 and 18 robots,
depending on the complexity of the door design and the degree to which people wereused to load or transfer parts and subassemblies.
Finally, each company has adopted different locating schemes. Hinges were observedwith one bolt hole, two bolt holes, and two bolt holes plus a locator stud for a total ofthree holes. Hinges come off doors, hinges come apart, and (in one company visited 7
years ago) hinges come off car bodies. Some doors have hinges with integral checks
while others have separate checks. Some companies locate door outer panels to inners onholes while others use hem surfaces. Some use locator holes on doors to index them tocar bodies while others measure gaps and position the doors to suit using robots or
manual techniques.

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Table 1. Summary of Findings
Company / Topic
Type of car at visitA
Sedan, mid-market

Door architecture(arch) at visit

Stamped inner andouter

Other door arch
remarks

One-piece inner

Stamped or roll
formed upper
reinforcement, one
piece innerIs this the standard
arch?
Reason for
adopting this arch

No

Emerging as thestandard
Simple, stiff, can’t
see a reason forusing roll-form
frame arch

Other
standardized items?

Date of start ofstandardization
What CAE exists

No standard arch

B
Sedan, mid-upmarket
Stamped inner andouter, outer
occupies lower half
onlyC
Sedan, mid-market
Roll-frame upper
welded to stamped
lower after lower
inner and outer arehemmed (smallest
hemmer seen)
Two-gauge inner spot
welded during door
buildup, threaded
hinge reinforcements
weld directly to innerYes

D
Sedan, economy
marketStamped inner and
outer

E
SUV

One-piece inner,
separate nut plate
reinforcement, nuts
loose in pockets inthis reinforcementNo

Two-gauge innerlaser welded prior todoor buildup; hinge
studs welded directly
to innerYes for this family ofvehiclesStamped inner andouter, outer occupies
lower half only

Simple, stiff

No standard arch

Hinges, latches

Hinges, latches, door
handles, window
regulator, static anddynamic seals

Seeking but notachieved yet

No

Still developing

5 years ago forcomponents

5 to 10 years ago

Still developing

Not applicable

Partial DCE*

Partial DCE

Regressions for DCE,
blowout, tip

Packaging
methodology in
CAD, partial DCE

DCE emerging, noise
matureF
Sedan, mid-upmarket
Stamped inner andouter, outer occupies
lower half only

One-piece inner,
separate nut plate
reinforcement, rollform frame
reinforcement
Emerging
Stiffer than roll
formed frame archand much stiffer thanstamped plus rollform upper
reinforcement
Hinges, inner andouter handles, latches,
window regulator,
static and dynamic
seals, motors
10 years ago forcomponents, 5 years
ago for door
DCE

7Company / Topic
Ability to predictdoor closing effort

A
Depends on
prototypes

B
Good understandingof current design

C
Excellent
understanding ofstandard design
Function-driven,strict adherence tostandard design

D
Some

E
Some

F
Based on CAE andfamiliar design

Basis of door
design org andmanagement of
attributes

Component-driven,system coordinator
for attributes

Component-driven,
will appoint an
integration manager
soon“Door architect”
coordinates
requirements, “doorpilot” coordinates
components, both
watch attributes
Door sheet metal,
mechanicals, anddoor glass

Function-driven,
expert experience

Door design manager
balances attributes,
plus competence
centers for subfunctions andcomponents
Entire car glass
perimeter, door sheet
metal, mechanicals

What’s in door
designresponsibility
scope
Generaldescription of door
mounting

Door sheet metal
and mechanicals

Door sheet metal
and mechanicals

Door sheet metal andmechanicals

Door inner has
hinges located toinner panel masterlocators. Mounting
fixture holds dooron outer panel holelocators andindexes to body
locators

Robot holds door,
laser measures gaps
and dist to seal, 2ndrobot tightens allbolts and nuts

Small fixture indexes
to body locators andmounts hinges tobody; doors attach via
net holes on hinges
and shoulder bolts

Door inner withhinges indexes via
master locators to
fixture installed indoor opening thatindexes to body
locators

Upper hinge plate
located to hinge
reinforcement via
threaded hole; lower
hinge plate indexed
via threaded hole toinner panel masterlocators; holes on
inner and outer usedduring hemming

Nuts loose in pockets
in reinforcement;
reinforcement locatedto inner masterlocators

Door has hinges
located to outer panel
hems. Fixtureindexes to body
locators, holds dooron outer panel hems.
In-out set by shims in
0.5mm increments
based on 2x/day
CMM check of seal
gap. Operators adjust
F/A door position toachieve gaps.
Holes on door inner,
studs on hinge plates,
outer located on hemedges for hemming

Locators usedduring door
buildup

Master locators ondoor inner, holes ondoor outer

Hinge plates
located to inner via
threaded holes thatare not used as
locators; masterlocators on inner,hem surfaces onouter used duringhemming

Door sheet metal andmechanicals

Fixture mounts front
and rear hinges tobody at once,indexing on body
locators at hinge
mount area fwd andstriker area aft.
Hinges have locator
cones that mate todoor locators. Lower
cone is loose and istightened to set inout.
Threaded hole andsmall clear hole inhinge plates, locators
on hinge
reinforcement, locatorholes on inner panel,
locator holes on outerpanel used forhemming8Company / Topic
Locators used forhingesA
Hinges located U/Dand I/O from inner,
location held withepoxy washer

B
Hinges have open
holes on both flaps

C
Hinges mounted tocar body using fixture
that holds hinges by
net pierced hole indoor side flap

Locators used fordoor mounting

Door outer locatorsand body locators,
epoxy washer set
during paint curing

Laser measurementof gaps andflushness, then bolts
are tightened

Door bolted to hinge
flap via shoulder bolt
through net piercedhole

Are screw threads(internal orexternal) used inlocation?

No (all bolts go
through open holes
except one bolt
goes through net
hole in epoxy
washer)Hinge comes off
door, epoxy washer
holds door location
on door side hingeflap
No except forsealant at innerouter jointNo

No (all bolts go
through open holes)

Door-off method

Robotics used fordoor buildup
Robotics used fordoor mounting
Other aspects ofdoor mounting

One door at a timeD
Studs onreinforcement used toplace hinge locator
studs in loose nuts;
hinges index to thesestuds
Door inner masters
mate to fixtureindexed to bodyE
Outer hem surfaces
used to locate hinges
on doorF
Cones on hinges go
into large hole on
hinge plates

Outer hem surfaces
for U/D and F/A, andshims for I/O

Yes

Yes

No (all bolts go
through open holes)

Hinges mount tobody; fixture indexed
to body uses cone on
upper hinge to locate
it to fixture, rotatesdoor about X and setslower cone
Yes

Bolt comes out of
hinge

Shoulder bolt comesout of door side flap

Door side flap comes
off locator studs on
door

Bolt comes out of
hinge

Hinge comes off
door, uses cone forrelocating

Yes

No except for sealant
at inner-outer joint

Yes

Yes

Yes

Yes: one holds andmaneuvers door,
other tightens bolts
One door at a time

No

No

No

No

One door’s hinges at
a timeOne door at a time

One door at a time

Front and rear hinges
simultaneously by
one fixture

9Company / Topic
General layout ofdoor
manufacturing*

Degree of door
adjustment at final

A
Stamping far
remote frombuildup, buildup
remote frommounting
Considerable
hammering andbending by hand or
tools

B
Stamping nearremote frombuildup, buildup
near mounting

C
Stamping near-remotefrom buildup, buildup
right at mounting

D
Stamping near-remotefrom buildup, buildup
near mounting

E
Stamping nearbuildup, buildup
remote frommounting

F
Stamping near-remotefrom buildup, buildup
near mounting

A little hammering
plus hitting striker

A little hammering
plus hitting striker

A little hammering
plus hitting striker

A little hammering
plus hitting striker

None

Yes

Crews doing door
mounting and final
adjustment swap jobs
at mid-day
Yes

Other aspects ofdoor adjustment

Door passes thumbtest**No

Yes (Tested on
previous model)

Crews doing door
mounting and final
adjustment swap jobs
each week
Yes

No, but large integral
check closes the door

Notes: DCE = door closing effort. U/D = up/down. F/A = fore/aft. I/O = in/out. CMM = coordinate measuring machine. CAD = computer-aided design.
CAE = computer-aided engineering. *General Layout: Far remote= more than 100km, remote = more than 10 km, near-remote = more than 100m,
near = less than 100m, right at = less than 10m. **Thumb test: the front door is closed to the point where the latch gently rests on the striker. Other
doors and windows are closed. The tester pushes sharply on the door with the thumb, which is placed on the door at the rear hem near the window belt.
If the door closes, it is said to pass the thumb test. In the 1990s the author found that doors in this position had to be pushed with the foot to close them.

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VI.

Discussion

Automobiles are complex products. Their design and manufacture require that they be
decomposed into manageable subunits, but there is no unique best decomposition. The
components at the bottom of the decomposition, at least with current technology, seemdistinct and easy to separate. Examples include wheels, exhaust pipes, power steering
racks, shock absorbers, windshields, and headlights. But if we go up the decomposition
we find ambiguity about which subsystems these apparently separate components belong
to. Does glass belong to body? What about its effect on heat load and thus passenger
comfort systems? Do exhaust pipes belong to chassis (for packaging and vibration) or to
power train (for their role in emissions control)? Who should own the glass in doors?
Researchers have noted these difficulties. Both [MacDuffie] and [Fourcade] discuss theambiguities over what “module” means and present via interviews and detailed casestudies the problems that occur in engineering design and supply chain management
when module boundaries are set inappropriately. [Fine and Whitney] identify this as a
generic problem in make-buy decisions. Even though the parts are similar and assemble
to each other in similar ways, the question of who owns them during design cannot beanswered unambiguously. Hence we see different organizational assignments in different
companies. Doors are a particularly acute example.
The situation with doors is complicated by the fact that their attributes conflict.
Moreover, even though the closures designers own (that is, are responsible for) the
attributes, some of the design decisions that affect the attributes are controlled byorganizations that are outside the scope of closures design organizations, even those thatown all the glass. This means that closures designers lack the necessary freedom to maketheir design choices in a simple independent way. Instead, their decisions interact witheach other, not to mention that they interact with decisions made by others.
The result, not surprisingly, is that different companies have organized door design
differently. Even those (companies C, D, and F) that recognize the system nature ofdoors most clearly, have chosen different routes. The only common thread is a movetoward standardization, but even here there are differences, with Toyota being the mostcomprehensive (parts, architectures, and processes) as well as the most rigid.
Standardization freezes the complex decisions in a place where everyone understands theoutcomes. But such freezing can keep designs from evolving in useful or innovative
ways.
Other companies, including A, B, and F, hope to manage the complexity by means ofCAE. Neither standardization nor CAE solve the problem of ownership but each eases
the discussion and decision processes by presenting the organization with welldocumented or well-understood choices.

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Not only are many organizational structures used but many door designs are used as well.
All of them work to varying degrees but each represents a different endpoint in an overconstrained design space where no design can meet all the requirements ideally.
Less common than standardization is a move to emphasize the system nature of doors
explicitly in the organization. Again, different companies have done this in different
ways or to different degrees. Toyota retains a functional organization but ensures that
middle and senior managers are fluent in system thinking and understand how things
inter-relate [Sobek]. D has renamed its major engineering organizations and job titles toemphasize architecture and interactions. F assigns a manager to a car’s closures who is
responsible to the chief vehicle engineer for all door attributes. The other companies
visited have moved less decisively along this route but appear to recognize the value of
doing so.

VII. References[Baron] Baron, J., “Benchmark Study on Dimensional Automotive Door Quality,” Center
for Automotive Research, Ann Arbor, MI, 2001
http://www.cargroup.org/manufacturing.html[Eppinger et al] Eppinger, S. D., Whitney, D. E., Smith, R. P, and Gebala, D. A., "A
Model-Based Method for Organizing Tasks in Product Development," Research in
Engineering Design, (1994) 6: pp 1-13
[Fine and Whitney] Fine, Charles, and Whitney, Daniel, "Is the Make-Buy Decision aCore Competence?" Moreno Muffatto and Kulwant Pawar (eds.), Logistics in the
Information Age, Servizi Grafici Editoriali, Padova, Italy, 1999, pp. 31-63. Also
available at http://esd.mit.edu/esd_books/whitney/pdfs/make_buy.pdf[Fourcade] "Modularization in the Auto Industry: Can Manufacturer's Architectural
Strategies Meet Supplier's Sustainable Profit Trajectories?" (with C. Midler), Proceedingsof the FISITA World Automotive Congress, Barcelona, May 23-27, 2004.
[MacDuffie] “Modularity and the Automobile: What Happened When the Concept Hit
the Road” Wharton School University of Pennsylvania working paper v 4.4, May 26,
2006[Noor] Noor, M. J., “A Comprehensive Approach to Complex System ProductDevelopment: Operations Management Tools Applied to Automotive Design” MIT
Mechanical Engineering Department Thesis, May 2007
[Peschard and Whitney] Peschard, G. and Whitney, D. “Cost and Performance Efficiencyof Automobile Engine Plants,” http://esd.mit.edu/esd_books/whitney/pdfs/Engine.pdf[Sobek] Sobek, Durward K, II, “Principles that Shape Product Development Systems: A
Toyota-Chrysler Comparison,” PhD Thesis, University of Michigan, 1997

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[Stevens] Stevens, M., “How to Develop and Deploy System Integrators Within
Component-focused Engineering Organizations,” MIT SDM Thesis, January 2005.
[Whitney] Whitney, D. E., Mechanical Assemblies: Their Design, Manufacture, and Rolein Product Development, New York: Oxford University Press, 2004
[Whitney et al] Whitney, D. E., Heller, D. A., Higashi, H., and Fukuzawa, M.
“Production Engineering as System Integrator? A Research Note based on a Study ofDoor Engineering and Assembly at Toyota Motor Corporation,” University of Tokyo
Manufacturing Management Research Center discussion series paper MMRC-169, June,
2007. Available at http://www.ut-mmrc.jp/