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Toyota
Production
System
Lecturer:
Stanley
B.
Gershwi
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TPS
• Primary source: Toyota Production System by Ya
Monden
•
See
also:
“Decoding
the
DNA
of
the
Toyota
Produ
System” by Steven Spear and H. Kent Bowen, Har
Business
Review
,
September-October,
1999.
• Goals of TPS:
� reduction of costs — ie, reduction of waste
�
increase
of
total
sales/total
assets
� improvement of total productivity
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Context
TPS
• Developed by Toyota after WWII:
� In the postwar period, the West was pros
was
important
to
satisfy
demand.
�
Japan
was
poor.
Cost
minimization
and
ewere
most
important.
�
TPS
is
low
tech,
not
dependent
on
comp
actions
easily
understandable.
Currently TPS is widely imitated Ford P
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Basic ideas
TPS
Concepts
•
Continuous
flow
of
production
� Just in time: produce necessary units in
necessary
quantities
at
the
necessary
tim
�
“Autonomation”
—
jidoka
—
autonomouscontrol.
• Flexible work-force — shojinka.
•
Creative
thinking
—
soikufu
—
capitalizing
i
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Basic ideas
TPS
Systems
and
me
• kanban
• production smoothing
• reduction of setup time
•
standardization
of
operations
to
attain
line
• machine layout and multi-function workers
•
improvement
activities
• visual control
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Basic ideas
TPS
“DNA”
Spear and Bowen: “We found that, for outsiders, the
understand
that
the
Toyota
Production
System
createcommunity of scientists.”
The Four Rules:
1. All work shall be highly specified as to content, seq
timing, and outcome.
2.
Every
customer
supplier
connection
must
be
directmust be an unambiguous yes-or-no way to send re
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Basic ideas
TPS
Just in tim
• In final assembly of a car, the subassemblies arrive
they
are
needed.
• Inventories are therefore not needed.
• Cannot be achieved by central planning.
• People at each process withdraw from previous pro
what they need.
•
People
at
each
process
produce
what
is
necessary
what
has
been
taken
by
next
process.
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Basic ideas
TPS
Kanban
syst
• A part of TPS.
•
An
information
system
to
control
production
quantit
• Kanban: a card in rectangular vinyl envelope.
• Withdrawal kanban: describes quantity that subseq
process must withdraw.
• Production-ordering kanban: describes quantity tha
process must produce.
• Kanbans circulate within factories and between fac
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TPS
a b A
Withdrawal kanban Production kanban
Basic ideas
Kanban
syst
• Products: A,
B C • Components
•
a’s
and
b’s
a
at
upstream
production
k
attached to p
they
are
put
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TPS
a b A
Withdrawal kanban Production kanban
Basic ideas
Kanban
syst
• Worker from
downstream
withdraws
so
from
storagewithdrawal k
B C
• He detaches
production
k
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Basic ideas
TPS
Kanban
syst
a b A
Withdrawal kanban Production kanban
B C
•
Unattached
kanbans
are
to
tell
upstre
how much to
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Basic ideas
TPS
Fine
tuning
• Engine line normally producing 100 engine
• Next process requests lots of 5 with withdr
kanban.
•
Withdrawals
occur
20
times
per
day.
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Basic ideas
TPS
Fine
tuning
• If demand is reduced to 90 per day, withdr
occur
18
times
per
day.
• The process is stopped after 90 are produ
•
If
demand
is
increased
to
110
per
day,
withoccur
22
times
per
day.
• The additional engines are produced in ov
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Basic ideas
TPS
Production
smo
• If kanban is used and production at a stag
fluctuates,
the
previous
stage
must
hold
in
and
have
excess
capacity.
•
Therefore,
final
assembly
will
use
minimal
reduce fluctuation.
• Also, final assembly will withdraw small lot
previous
stages.
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Basic ideas
TPS
Example
•
Plant
produces
10,000
Toyota
Coronas
in
� 5,000 sedans, 2,500 hardtops, 2,500 wa
• 1 month = 20 eight-hour shifts
•
Production
is
divided
equally.
Every
shift:
�
250
sedans,
125
hardtops,
125
wagons
•
eight-hour
shift
=
480
minutes.
Therefore
utime = 480/500 = .96 minute = 57.5 secon
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Basic ideas
TPS
Example
•
One
sedan
must
be
generated
every
1
min
• One hardtop must be generated every 3 m
• One wagon must be generated every 3 mi
•
Possible
sequence:
sedan,
wagon,
sedan,sedan,
wagon,
sedan,
hardtop,
...
•
As
long
as
there
is
no
setup
cost,
a
seque
this
is
preferable
because
it
minimizes
inve
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Basic ideas
TPS
Setups
• Major emphasis on reduction of setup time
• Pressing department setup times:
� 2-3 hours, 1945-1954.
�
15
min.,
1955-1964.
�
3
min.
after
1970.
• External setup: setup work that can be do
operation
is
taking
place.
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Basic ideas
TPS
Process
Des
• Previous layout: rows of machines organiz
(lathe,
mill,
etc.),
and
one
worker
per
mach
• TPS layout:
�
Machines
organized
to
smooth
material
fl�
Each
worker
handles
three
different
mac
� Worker deals with one piece at a time (o
flow)
.
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Basic ideas
TPS
Process
Des
• Benefits
�
inventory
reduced
� fewer workers needed
�
workers
feel
better
about
their
jobs
�
workers
become
part
of
factory
team
bec
their
increased
knowledge
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Basic ideas
TPS
Job Standardiz
• Late in the month, central planning office t
production
department
the
volume
require
next
month
—
ie,
the
next
month’s
takt
tim
system).
• Process managers determine how many w
needed.
•
Lines
are
rebalanced
so
cycle
time
=
takt
t
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Basic ideas
TPS
Autonomati
• Not automation.
•
“The
autonomous
check
of
the
abnormal
in
process.”
•
Built-in
mechanism
to
prevent
production
oproducts.
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Basic ideas
TPS
Autonomati
• If a machine produces a defect, it stops the
line.
• For manual operations, workers can stop t
line.
• Pokayoke: “foolproof” system for checking
prevent
defects.
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Basic ideas
TPS
Visible
control
s
• Andon: electric light board.
•
Board
is
large
and
high
and
therefore
visib
points in factory.
•
When
a
worker
delays
a
job,
he
turns
on
alight.
• When a worker stops a job, he turns on a
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Basic ideas
TPS
Improvement
ac
•
Worker
suggestions
via Quality Control (Q
•
This
provides
good
ideas,
and
workers
bec
more
part
of
the
team.
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Kanban
•
Kanban
is not TPS. Kanban is a subsyste
•
Information
flow
system.
• Low level shop floor control.
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Non-kanban syst
Kanban
• In ordinary production control systems, sch
are
issued
to
all
processes
(push
).
• It is difficult to adapt to demand fluctuation
disruptions,
etc.
• Therefore, the company must hold invento
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Pull
Kanban
• Kanban is a Pull system .
•
When
scheduling
changes
occur,
it
is
enou
notify final assembly.
•
All
preceding
stages
learn
about
changes the
kanban
system.
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Two cards
Kanban
Simplified
fl
Production kanban Withdrawal kanban M
movement movementm
• When a machine is available, and it has a
kanban, a part and a withdrawal kanban m
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Two cards
Kanban
Simplified
fl
Production kanban Withdrawal kanban M
movement movementm
• After the operation, the withdrawal kanban
the
upstream
buffer,
and
a
part
and
a
prod
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Two cards
Kanban
Simplified
fl
Production kanban Withdrawal kanban M
movement movementm
• When a buffer has a free withdrawal kanba
moves
to
it
from
the
upstream
buffer,
and
a
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Two cards
Kanban
Simplified
fl
•
The
number
of
each
kind
of
kanban
is
fixestage.
• If a machine fails, the next machine can ke
operating
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Two cards
Kanban
Simplified
fl
• Each box in this picture can represent a
sub-process,
consisting
of
several
machine
than just a single machine.
�
It
could
be
an
entire
factory.
• Therefore, flow into and out of a box need
same, at each time instant.
•
Actual
movement
of
kanbans
can
be
more
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Two cards
Kanban
Withdrawal
ka
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Two cards
Kanban
Production-orderin
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Other kanbans
Kanban
• Supplier kanban: same as withdrawal, ex
external
supplier
• Signal kanban: same as production kanba
sent
to
production
station
when
inventory
gto
a
reorder
point.
• Material requisition kanban: same as prod
kanban,
but
sent
to
a
material
storage
arealocal inventory goes down to a reorder poi
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Rules
Kanban
1.
Each
process
withdraws
the necessary pr
from
the
previous
in
necessary
quantities
necessary time.
•
To
enforce
this,
workers
must
first
be
wo•
Kanbans
must
be
attached
to
the
produc
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Rules
Kanban
2.
Each
process
produces
only
what
is
withd
subsequent
process.
3. Defective products are never moved to nex
4.
The
number
of
kanbans
should
be
minimiz5.
The
kanban
system
should
be
used
to
ada
fluctuations
in
demand.
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Smoothing Total Productio
Production
Quantities
• Minimize the variance of total output in a p
�
Produce
the
same
amount
every
day.
• Amount produced in a day is the total for a
period
(eg,
one
month)
divided
by
the
numdays
in
a
month.
� The planning period should be as short a
possible.
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Smoothing Total Productio
Production
Quantities
Waste
Reduc
•
System
must
be
set
up
for
peak
demand
in
When
demand
is
less
than
the
peak,
capawasted.
•
When
production
is
not
smoothed,
inventoaccumulates between stages.
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Smoothing Total Productio
Production
Quantities
Adaptation
to
De
• If demand increases, hire temporary worke
shifts,
etc.
• If demand decreases,
�
dismiss
temporary
workers,
�
transfer
workers
to
lines
with
increased
d
� decrease overtime,
�
fill
up
workers’
time
with
quality
control
m
i i
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Smoothing Total Productio
Production
Quantities
Each
Model’s
Pro
• Mix models to minimize inventory.
•
Mix
models
to
maximize
utilization.
Examp
�A parts require 70 minutes in a line; B p
require
60
minutes;
C
parts
require
50
m� If they are produced
AAAA...BBBB...CCCC...,
the
produ
of
the
line
changes
over
time
(1/70;
1/60� If they are producedABCABCABCA
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Smoothing Comparison with
Production
Quantities
• MRP: more data handling.
•
MRP:
usually
weekly
time
buckets.
• Kanban designed to absorb fluctuations; M
recalculate
master
production
schedule
we• MRP may be better with very short produc
where
smoothing
is
difficult.
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5S
•
Seiri:
throw
out
what
you
don’t
need.
•
Seiton:
lay
out
things
neatly.
• Seiso: clean up
•
Seiketsu:
standardize
above
activities.
• Shitsuke: inspire workers, and have them
conforming
to
rules
a
habit.
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TPS
Toyota’s Notion of th
A
common
vis
The output of an ideal person, group of people, or m
•
is
defect
free
(features,
performance
the
customer
• can be delivered one request at a time (a batch siz
• can be supplied on demand in the version requeste
• can be delivered immediately;
• can be produced without wasting any materials, lab
or
other
resources
(such
as
costs
associated
with
i
• can be produced in a work environment that is safe
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TPS
• This has been a very brief overview.
•
TPS
has
been
extremely
successful.
• TPS has been extremely influential.
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