Ensayo Mixto

A Book Review:
Lean Thinking by Womack and Jones

Assignment for ESD.83:
Research Seminar in Engineering Systems

Prepared by
Annalisa L. Weigel
November 2000

Annalisa L. Weigel

Book Review

“We can lick gravity, but sometimes the paperwork is overwhelming.”
– Werner von Braun

Summary of Lean Thinking
Lean Thinking: Banish Waste and Create Wealth in Your Corporation by JamesP. Womack and
Daniel T. Jones was published in 1996 by Simon & Schuster, New York. This book follows a
previous highly successful book by Womack, Jones and Roos entitled The Machine That
Changed the World. Both books address the revolution in manufacturing represented by the
Toyota Production System of the Toyota Corporation of Japan. This type of manufacturing
system is called a “leansystem” and is contrasted throughout the book with the traditional “mass
production” system of manufacturing epitomized by batch-and-queue methods.
The authors argue that a lean way of thinking allows companies to “specify value, line up valuecreating actions in the best sequence, conduct these activities without interruption whenever
someone requests them, and perform them more and moreeffectively. 1 ” This statement leads to
the five principles of lean thinking: Value, Value Stream, Flow, Pull and Perfection.
Value is defined by the authors as a “capability provided to customer at the right time at an
appropriate price, as defined in each case by the customer. 2 ” Value is the critical starting point
for lean thinking, and can only be defined by the ultimate end customer. The ultimateend
customer, or the user of the product, is contrasted with interim customers, such sales, marketing,
distribution, suppliers, etc. Value also is product-specific, and the authors argue it is only
meaningful when expressed in terms of a specific product.
The value stream is defined in Lean Thinking as the set of all the “specific activities required to
design, order, and provide a specificproduct, from concept to launch, order to delivery, and raw
materials into the hands of the customer. 3 ” To create a value stream, describe what happens to a
product at each step in its production, from design to order to raw material to delivery. There are
three types of activities in the value stream – one kind adds value, and the other two are “muda”
(the Japanese word for waste) 4 :
•
••

1
2
3
4

Value-Added : Those activties that unambiguously create value.
Type One Muda : Activities that create no value but seem to be unavoidable with
current technologies or production assets.
Type Two Muda: Activities that create no value and are immediately avoidable.

Womack & Jones. Lean Thinking . New York: Simon & Schuster, 1996. p. 15.
Womack & Jones, p. 311.
Womack &Jones, p. 311.
All three definitions from Womack & Jones, p. 20.

ESD.83, Fall 2000

Page 2

Annalisa L. Weigel

Book Review

Some examples of muda are mistakes which require rectification, groups of people in a
downstream activity waiting on an upstream activity, or goods which don’t meet the needs of the
customer.
The lean principle of flow is defined as the “progressiveachievement of tasks along the value
stream so that a product proceeds from design to launch, order to delivery and raw materials into
the hands of the customer with no stoppages, scrap or backflows. 5 ” This translates as a directive
to abandon the traditional batch-and-queue mode of thinking that seems commonsense to most.
Ways to foster flow include enabling quick changes of tools in manufacturing,as well as rightsizing machines and locating sequential steps adjacent to one another.
The fourth lean principle of pull is defined by the authors as a “system of cascading production
and delivery instructions from downstream to upstream in which nothing is produced by the
upstream supplier until the downstream customer signals a need. 6 ” This is in contrast with
pushing products through a...