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Quality Assurance by D. H. Stamatis

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103
9
Lean Manufacturing
Overview
In the last chapter, we introduced the concept of a visual factory as a fundamental
approach to improvement. In this chapter, we will discuss the notion of removing
waste (nonvalue activities) not only from individual processes but also from the
entire organization. The terminology for this methodology is Lean manufacturing.
Even though the consensus is that Lean manufacturing as applied today
is derived from Toyota’s principles of Lean production methods, the roots of
the process are in Henry Fords integrated philosophy in the Rouge Complex
in Dearborn, Michigan, in the early 1900s. The difference between Ford’s
approach and Toyotas is that Ford’s method was static, whereas Toyotas
became a dynamic process.
The term Lean manufacturing was coined by Krafcik (1988) and made popu-
lar by Womack, Jones, and Roos (1991). If the reader is interested in more details
about the history of Lean, Holweg (2007) gives a complete historical account.
The reader will notice that we identied Lean as a methodology and not a
tool. That is because Lean incorporates many tools to accomplish its mission,
which is elimination or reduction of waste—however dened. Some of these
tools are Single Minute Exchange of Dies (SMED), Value Stream Mapping
(VSM or VM), 6S, Kanban (pull system), Poka yoke (error/mistake proof-
ing), Total Productive Maintenance (TPM), rank order clustering, Statistical
Process Control (SPC/control charts), redesigning working cells, multipro-
cess handling, single point scheduling, and many others.
In essence, these and many other tools within Lean are implemented with the
intention of increasing quality while at the same time reducing production time
and costs. This is accomplished by separating the waste (muda) into three catego-
ries, which are based on Toyota’s system of preventive maintenance. They are
1. Muda (non-value-adding work). Focusing on the system, not reduc-
tion per se in individual pockets of a process. Generally, it is a reactive
activity of identifying waste and is seen through variation in output.
2. Muri (overburden). Focusing on the preparation and planning of the
process, or what work can be avoided proactively by design.
104 Quality Assurance
3. Mura (unevenness). Focusing on production leveling by utiliz-
ing a pull system such as the Kanban or the Heijunka box (SMED)
approaches. This focus is predominantly on how the work design is
implemented and the elimination of uctuation at the scheduling or
operations level, such as quality and volume.
To recognize and do something about these wastes, management must
take an active role. Its basic role is to examine the muda in the processes and
eliminate the deeper causes by considering the connections to the muri and
mura of the system. The muda and mura inconsistencies must be fed back to
the muri, or planning, stage for the next project. To optimize this link, there
are several assumptions that must be considered so that the three categories
of waste will work. The assumptions are
1. Pull processing
2. Perfect rst-time quality
3. Waste minimization
4. Continuous improvement
5. Flexibility
6. Building and maintaining a long-term relationship with suppliers
7. Autonomation (the basic idea of jidoka ) may be described as
intelligent automation or automation with a human touch
8. Load leveling
9. Production ow (just-in-time, JIT)
10. Visual control
In essence, the results of understanding these three waste categories are to
get the right things to the right place at the right time in the right quantity
to achieve perfect workow, while minimizing waste and being exible and
able to change. In order for that exibility and change to take place within an
organization, they have to be understood, appreciated, and embraced by the
actual employees who build the products (or carry out the service) and there-
fore own the processes that deliver the value. It is of paramount importance
that in addition to the employees being on board with the implementation
process, the culture and management of the organization must be ready to
embrace the change enthusiastically and be committed to removing waste.
It is worth mentioning here to practice Toyotas mentoring process of Sempai
(senior) and Kohai (junior), which has proved to be one of the best ways to
foster Lean thinking up and down the organizational structure—including
suppliers. Without a strong commitment, nothing will happen in the end.
Womack and Jones (1996) suggest an additional strategy for encouraging
companies, organizations, and teams to seek outside, third-party experts, who
can provide unbiased advice and coaching via the concept of a Lean Sensei.

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