toyota production system - mit

8/9/2019 Toyota Production System - MIT

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Toyota

Production

System

Lecturer:

Stanley

B.

Gershwi


2/49

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


4/49


5/49

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


6/49

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


7/49

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


8/49


9/49

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.


10/49

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


11/49

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


12/49

TPS

a b A


Basic ideas

Kanban

syst

• Worker from

downstream

withdraws

so

from

storagewithdrawal k

B C

• He detaches

production

k


13/49

Basic ideas

TPS

Kanban

syst

a b A


B C

•

Unattached

kanbans

are

to

tell

upstre

how much to


14/49

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.


15/49

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


16/49

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.


17/49

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


18/49

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


19/49

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.


20/49

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)

.


21/49

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


22/49


23/49

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


24/49

Basic ideas

TPS

Autonomati

• Not automation.

•

“The

autonomous

check

of

the

abnormal

in

process.”

•

Built-in

mechanism

to

prevent

production

oproducts.


25/49

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.


26/49

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


27/49

Basic ideas

TPS

Improvement

ac

•

Worker

suggestions

via Quality Control (Q

•

This

provides

good

ideas,

and

workers

bec

more

part

of

the

team.


28/49

Kanban

•

Kanban

is not TPS. Kanban is a subsyste

•

Information

flow

system.

• Low level shop floor control.


29/49

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


30/49

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.


31/49

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


32/49

Two cards

Kanban

Simplified

fl


movement movementm

• After the operation, the withdrawal kanban

the

upstream

buffer,

and

a

part

and

a

prod


33/49

Two cards

Kanban

Simplified

fl


movement movementm

• When a buffer has a free withdrawal kanba

moves

to

it

from

the

upstream

buffer,

and

a


34/49

Two cards

Kanban

Simplified

fl

•

The

number

of

each

kind

of

kanban

is

fixestage.

• If a machine fails, the next machine can ke

operating


35/49

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


36/49

Two cards

Kanban

Withdrawal

ka


37/49

Two cards

Kanban

Production-orderin


38/49

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


39/49

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


40/49

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.


41/49

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.


42/49


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.


43/49


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


44/49


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


45/49

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.


46/49

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.


47/49

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


48/49

TPS

• This has been a very brief overview.

•

TPS

has

been

extremely

successful.

• TPS has been extremely influential.


49/49

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2.854 / 2.853 Introduction to Manufacturing Systems

Fall 2010

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