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Sekisui's Three-Day House
Steps Toward Upost-JIT, Post-TOM" Manufacturing
Robert W. Hall and Yoshinori Yamada
ekisui Housing Division builds 80 percent of a
house in three days. Fabrication of parts takes
a day, assembly of modules another day, and
after overnight transport to the site, erection takes
less than a day. The process reminds Americans of
an old-fashioned barn raising, except that a modern
house is much more complex than a barn.
Traditionally, Japanese houses were lightly
constructed. Many lasted only 15 years. In a land
where typhoons and earthquakes were part of everyone's experience, common sense dictated not building an expensive house if it would just blow away,
and not building a heavy one if it would likely fall
on you.
Asteel-framed Sekisui Heim house departs
from old Japanese thinking. The modules are
designed and tested to withstand 240 m.p.h.
typhoon winds and a 7.8 Richter earthquake. Sekisui sells peace of mind as well as new technology.
Sekisui appeals to young professionals, and
especially those who are technically-oriented. The
modules can be fully wired to accept appliances
and telecommunications equipment. A"smart"
Sekisui house has timers and controls for lights
and appliances, and these can be reprogrammed
by telephone if desired. Since Sekisui began as a
chemical company synthesiZing building materials, they have always had a significant research
function. Most building contractors think they
cannot afford formal R&D.
S
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Target
Sekisui's R&D centers on a testing laboratory
built especially to research complete, integrated
housing modules and systems, including a wind
tunnel and vibration stands. The company prides
itself on advanced materials research for housing.
To bring innovation and new technology to the
customers, the average age of the Sekisui Housing
Division R&D staff is 28.
The design and production phases of building this kind of house are very instructive to manufacturers, but that is only part of the housing
business. Almost as many people work in Sekisui
sales offices and field service operations as in the
plants. In seventy percent of the cases, old houses
must be removed from the site of new ones. Site
preparation averages about ten days. Trimming,
landscaping, inspections, and follow-up consume
about another thirty days after erection. During
this time, Sekisui field crews want to complete the
"punch list" details from the inspections and the
inevitable changes suggested by customers. In
Japan, inspections by the lending institutions are
generally tougher than those by government
authorities. "Punch work" is more difficult after
the move-in. Many construction companies try to
evade as much of it as possible because punch work
is a profit eater, but being able to do it right is the
reason Sekisui competes on quality, not price.
Although only 20 percent of the labor is done
on-site, the customer leadtime from order entry to
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move-in is about 40 days. That leadtime represents a
challenge for further improvement.
The average Sekisui house contains about 1400
square feet, and is composed of 13 modules. Houses
range in size from about 1000 square feet to 3000 square
feet, and cost $100,000 to $400,000, not counting land
prices. Houses near urban areas are cheap compared to
the value of the land they sit on. The cost of having real
estate unoccupied during construction weighs on owners'
minds and pocketbooks, which stimulates the need to
complete a house quickly.
Attributes of a Quality House
The Sekisui attributes of a quality house are:
1. Safety: Besides standing up to typhoons and
earthquakes, a house should be fire resistant. The
current materials standard is a 15-minute delay
before fire can consume a house, and the firewarning system should be fail-safe. Houses built in
snow-belt regions should hold up to 15 meters of
snow on the roof - well beyond anything expected.
2. Durability: Ahouse should have a long life.
Materials should be resistant to corrosion and insect
attack. In addition, the modular design should make
it easy to retrofit expansions or changes with little
evidence of the later modifications. Sekisui fully
guarantees each house for ten years against almost
anything.
3. Living Comfort: The heating, lighting, and
communications systems should be initially designed
as the customer wants. As customers discover oversights, or as their needs change, later modifications of
these systems should also be easy to make. The house
should be easy to keep clean using spill-resistant
materials, for example, and the maintenance should
also be easy and inexpensive. Sekisui sells houses
based on life-cycle costs, not initial cost.
4. Economy: The objective is to be competitive with
stick-built housing, still preferred by most buyers.
Currently, the initial cost per square meter is about
the same as stick-build, but the quality is higher.
5. Installation Speed: The primary urgency is in
supplying replacement houses. The total on-site
process is: raze, foundation preparation, erection,
interior/exterior finish, and inspection/changes. For
customer satisfaction, Sekisui does not want the
time-line of this process to ever exceed 50 days.
A typical finished Sekisui house.
Design System
Modules come in 24 standard sizes and are
designed to enable overall structures that easily pass
Japanese building codes and lending institution expectations. Some modules are small "bathrooms," and
some are large living spaces. All can be finished with
unique design features according to the wishes of the
owner - different windows, doors, built-in appliances,
finishes, etc.
Owners guide the design of their own house on a
CAD system at the sales office. Those with the wherewithal can exercise greater creativity than merely selecting
options. However, Sekisui's CAD system for customers is
presently limited to a flat screen; virtual reality is not
used to assist customers to visualize the house, as has
been demonstrated on American television.
The average house contains 28,000 part numbers.
In complexity, Sekisui rates it above an automobile (46000 part numbers), but much simpler than a commercial jet airplane (over a million part numbers).
One of the keys to the three-day house is tight
dimensional tolerances. Sekisui maintains plus or minus
one millimeter dimensions everywhere in construction
- simple to remember, and everything fits the first time.
For example, installing kitchen cabinets in stick-built
houses often requires "dimensional adjustments" somewhere, even when irregular fits are covered by wide molding or other trim. ASekisui house is designed so that
everything fits the first time.
The technical capabilities of the CAD system are
basic. Work is generally done in 2-D, with limited use of
3-D views, but Sekisui makes the most of it. Design
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july/August 1993
To accomplish everything within minimum leadtime, information going to suppliers and to Sekisui
plants must be nearly perfect. The quality objective is
fail-safe, no-defect construction, so both the design and
the production processes are laden with fail-safe checks.
For example, the design system converts the wiring
requirements to bills of materials with color coded wire
that facilitates error-free connections both in the module assembly plants and in the field.
In addition, sales advisors and detailing engineers
closely monitor their own work. Detailing room bulletin boards are covered with the record of error-free
work by each detailer and their plans for improvement.
One of the objectives of both training and system modification is eliminating the causes of error.
Field assembly of modules.
Materials System
Heim house module assembly line.
Sekisui employees
are very proud that
no saws) planes) or
other dimensional
adjustment tools
are permitted in the
assembly plant meaning everyone
must do their job
correctly the first
time.
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Target
begins with a customer in a field office. Asales agent
and a technical advisor assist the customers to develop
their own plans directly in the CAD system. The version
used in the sales offices uses "artificial intelligence"
routines to estimate the cost of designs. If a customer
wants an extra bathroom which necessitates reconfiguring the entire layout, the system will cough up a cost
estimate for the change on the spot.
On average, it takes about a month to complete a
sale and ready each customer's plan for order entry.
The design is downloaded from the sales office to the
nearest of the seven Sekisui housing plants unless it is
overloaded. At the plant, order entry engineers check
each plan and finish the details necessary to ready it for
production. The detailing takes one or two hours.
The Tokyo Heim Plant is a good example of the
Sekisui factory system. In 1992, it had a capacity of
6000 steel-framed modules per month, plus 1300 twoby-four modules. The assembly plant is fed by a fabrication plant, and all the Sekisui employees are very
proud that no saws, planes, or other dimensional
adjustment tools are permitted in the assembly plant
- meaning everyone must do their job correctly the
first time.
Each Heim module baSically consists of a steel
box framed with angle iron. As much content as possible is filled into each module at the plant - walls,
flooring, wiring, plumbing, fixtures, built-in cabinets
and appliances, doors, windows, and much of the trim.
No more than nine days of orders are in queue
before fabrication begins. This is the maximum leadtime allowed for suppliers to ready materials for delivery. Deliveries at assembly are expected to arrive no
more than four hours before needed. Only two percent
of incoming material must pass inspection. Naturally,
Sekisui is working to reduce incoming inspection to
zero. Actual inventory at assembly averages about three
hours. The workforce takes inventory and corrects the
records once a month. Total inventory, including fabrication and raw materials, is about four days.
About half of the parts are brought in using a Kanban system. The other half are job-specific components
brought in by a sequencing schedule. All these unique
components are conspicuously identified with a module
number and the customer's name. The plant does not
use bar codes in assembly. Bar codes cannot be read by
humans, and the scanning procedures take too long. The
irregular sizes of components and limited space thwart
automatic read stations.
The size of the materials used in housing makes
material handling and shipping a central operating
problem for the Tokyo Heim Plant. About 400 trucks
per day deliver material close to the point of use. The
plant makes maximum use of carts and dollies moveable by human power to minimize disruption from lift
truck traffic.
Sekisui Housing Division has about 200 suppliers
Thirty of them are classified in a special group with
whom Sekisui works closely to improve quality. Sekisui
suppliers receive payment bonuses or penalties depending
on the overall quality of their service to Sekisui.
The production planning system might be
described as a combination of MRP with JIT. The bill
of material is generated by the design system. Since
every house may have unique engineering, various
"artificial intelligence" rules and routines call out the
detailed materials to prevent oversights. The bill of
materials is essentially three levels - part, subassembly, and module. The critical feature is assuring that
all unique parts are identified with their modules, subassemblies, and owners because the system must print
J.D. labels for all of them.
After explosion, the customer-specific parts from
suppliers are transmitted to them with a standard leadtime of nine days. Common raw materials are time offset
for ordering from various suppliers. Since Sekisui's quality requirements are stiff, few raw materials can truly be
considered commodities, but some of the leadtimes are
long. For instance, most wood is imported, some from
North America.
From this point, the materials system becomes a
kanban and order sequencing system. It operates much
as does a sequencing schedule to bring in seats and other
major subassemblies to an automotive plant, except on a
broader scale.
Plant Operations
Fabrication and assembly of modules are paced by
the module assembly lines. The takt time (planned cycle
time between completion of modules) is three minutes.
Throughput time at assembly is three hours, covering all
operations from welding the steel frame to Sign-off of
each module to the shipping yard.
At the Tokyo Heim Plant, steel houses are assem-
A traditional Japanese house interior.
bled on two lines. Athird line is dedicated to the 1\vo-U
(2x4) wood frame houses. Though preferred by some
customers, the 1\vo-U house is more laborious to
assemble because Sekisui has so far not been able to
develop a nailing robot to fasten the wooden walls
together in a fixture.
For the steel frame modules, angle iron is
clamped in a fixture and welded by robots just as is
done with car bodies in an auto plant. The steel members of any module are apt to be uniquely pre-cut with
holes to accommodate whatever the owner has elected
to put in the module.
The same fixture and robots are flexible enough
to process any of the 24 module sizes in a lot size of one
in any sequence. Sekisui now believes that the process
for programming these robots has now been encased
with sufficient fail-safe provisions that it is essentially
error-free. Oapanese now sometimes refer to this condition as "Zero Defects," but the implication is much
stronger than that implied by the old American use of
the term.)
Fifteen inspectors work in the Tokyo Heim assembly plant. Most of the errors are missed operations, and
most inspection is to assure that work is complete. Any
worker can stop a line, but a manager cannot. The
workers religiously practice Jidoka - temporary stopping of operations for correction or improvement and have a program of Total Productive Maintenance.
The quality of work is measured using a system of
green, yellow, and red demarcations of defect rates. Yellow suggests corrective action; red that operations are
becoming unacceptable.
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July/August 1993
I
The Japanese tend toward building vertically because of limited land space.
The main lines move about eight feet per minute.
Materials are slotted to approximately the correct location
along the line, but irregular material content for each
module prevents material locations being as precise as in
an auto plant. Each line station is manned by a team of
workers. All workers must be familiar with work one station ahead and one behind. To keep the line moving with
a variable work content in each module, they must routinely float through three stations. Workers sight-read
instructions and drawings carried with each module
down the line. These drawings are generated by the system after the order entry engineers add detail to the
design that originated with the customer in a sales office.
Kitchen modules are significantly more complex
than most others, so they take more assembly labor,
which would drastically unbalance the line. Kitchen
modules are shunted to a side line for extra work using a
longer takt time.
The first station after frame weld mounts the exterior
walls on the frame. It is fed by a subassembly area about
100 ft. x 50 ft., extraordinarily small for the size and volume of material moving through it. To accomplish this
feat, the walls stand vertically on movable platforms. The
platforms themselves move in two directions so that the
work snakes through the area like a line at an airline
ticket counter. Each wall is stuffed with color-coded
wiring harness. Windows and doors are mounted later.
Workers must be highly skilled, but Sekisui prefers
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Target
not to hire artisans accomplished in stick-build construction to work in the plant - too hard to "untrain." Their
instinct is to adjust a part if it does not fit or work rather
than make permanent correction using the system. To
further discourage tinkering, the company also permits
no fabrication tools to be used in assembly.
Workers are high school graduates selected for their
promise in this kind of work. All must become adept at
reading drawings and instructions. However, Sekisui gives
little or no formal training on this. New workers receive
initial instruction in safety procedures and quality processes. Then they go to work in the plant where almost
everything else is learned by the buddy system.
All workers receive a salary. None are direct labor in
the traditional sense, but they are paid overtime. Their
average salary is eqUivalent to about $25 per hour, which
is comparable to wages paid to Japanese automobile
company workers.
Improvement processes are aggressive. Productivity
has been rising at a rate of ten percent per year. Sekisui's
business goal is to be able to reduce prices by three percent a year.
Significance
Sekisui Housing Division is an example of a
Japanese company evolving toward what the Japanese
themselves are beginning to call "post-TQM, post-JIT
operations." As can be seen, "post" does not signify that
operating excellence is no longer important. Rather, a
company like Sekisui, having mastered the basics of
excellence, must combine them with technology and
imagination to redefine the concept of of its business.
Anew business concept begins and ends with what
an enterprise can do for a customer. The Sekisui case
illustrates several aspects of a radically new approach to
business:
Involve the Customer in the Process. ASekisui customer can design his own house - within limits.
No customer can have anything imaginable. Many wild
ideas are illegal, illogical, ecologically harmful, annoying to others, or ridiculously expensive - but not all of
them. Sekisui's business concept is to make new ideas
possible, not impossible. Part of the service is educating
the customer about new possibilities and on how to function in a smart house.
Involving the customer in this way is what is meant
by "customer-in" manufacturing rather than "productout," which is researching what we think customers
want, building it (or committing to designs), and hoping
for the best. Another name for an involved customer is a
"prosumer," someone personally involved in the process
of creating their own products and services, which with
computer design is high-tech do-it-yourself.
Securing the Customer
When a customer of a three-day house later wants
to add-on or remodel, a company without access to the
CAD record has little chance of getting the business. In
fact, if anything in the house malfunctions, Sekisui is the
company most likely to get the call. (One can imagine
an owner wanting to keep the CAD record disk in a lock
box along with the deed just in case Sekisui goes out of
business or becomes unreasonable.)
Environmentally Sound
Sekisui has yet to emphasize this aspect of their
concept, but Sekisui modules can seemingly be refurbished and upgraded for many years unless severely damaged. If everyone in Japan went for a Sekisui-type house,
in a generation or so the housing market would start
shifting from new construction to maintenance.
Information-Based
The three-day house is impossible without computers - and without working through using them in
more imaginative ways. They bring the customer into
the process and enable "making anything in lot sizes of
one in any sequence," but with the efficiency of mass
production.
Total Operations System
Sekisui is approaching a different kind of operations system. In the current state, the plants are advanced
examples of the Toyota Production System, but greater
customer satisfaction with much less waste is still possible. One oppurtunity to decrease waste is Sekisui's
fledgling "JIT-MRP" system, which might be better
termed an "orchestration system." With consistent
improvements by both customer and suppliers, much
opportunity still exists to tighten operations with that
kind of system, but it only encompasses plant production.
The big opportunities are in design, materials,
and field systems. Highly durable materials that can
easily be disassembled and reused elsewhere present
opportunities never before considered. Lack of quality
and databases made it impossible. No one really knows
the magnitude of opportunity that is now presented. It's
too early in history.
© 1993AME®
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July/August 1993