When I started my career in
the electronics manufacturing during early 90s, six sigma was prevalent where
every company wanted to achieve 6 sigma qualities at that time. According to Wikipedia, six sigma approach
was pioneered by Motorola engineers in 80s for the purpose of process
improvement. This methodology focus on
data collection and statistical analysis of data, using quality tools for root
cause identification and action plan to address the root cause thru phase by
phase approach. It is then follow data
analysis using statistic to verify if there is significant follow by
standardize action plan to sustain the improvement. It had become a big phenomenon when Jack
Welch made six sigma GE business strategy in 1995. Several American based multinational corporations
followed suit and claimed to have huge saving therefore they are making profit
and in business the biggest incentive is profit $. The word is six sigma became catch phrase for most company top
management, therefore they “force” their
organization to establish six sigma projects everywhere irrespective if it is a suitable approach or not.
When we approach the 21st
century, lean concept practice by Toyota caught the attention of the western world
when Dr. Womack et al. release an iconic
book about lean (The Machine That Changed the
World) in the 90s. This book was based
on their research in MIT about innovative management and production system use
in Toyota. As lean tools are quite simple
and easy to adopt, a lot of company start to use the popular tools such as 5s,
standard work, poke-yoke (error proof), kaizen etc., with almost immediate
results seen. Thus lean slowly take over six sigma as the groundbreaking tool
in production and management.
By the time lean become
popular, many organizations had already adopted six sigma “culture”
religiously. At the same time most
management does not want to lose out to company who embraced lean which had
gain a block buster results, they start
to assimilate lean tools and thus the beginning of term lean six sigma. Most of the training companies start to rid
the wave of trend by offering Lean six sigma course.
Lean six sigma is a very
misguided term as both lean and six sigma are entirely different. Lean is a culture and six sigma is an
approach to reduce variation contributed by poor process control. Six sigma could be part of lean and not
vice versa.
Six sigma is a structured
variation reduction methodology. I found
that a lot of engineers who had study or deploy six sigma still do NOT
understand the real meaning of variation
reduction. I would like to use the
scenario below to illustrate the meaning of variation reduction. A manufacturing company found that their
product could not customer specification for length of 308.50+/-0.30
(308.20-308.80). Base on the data
collected for product length and plotted on the control chart on the left, it
seems some data already exceed or below spec.
The company had to reject the product which does mean customer
spec. The quality engineer decided to
use six sigma approach to improve the process in order to produce parts which
consistently meet customer spec. After
improvement, the quality engineer collect the product length data and plot in
control chart (right). It was found the product
length variation had reduced with tighter control limit as compare to the chart
on the left. It also show that the
product length can consistently meet customer spec, Thus variation of the product length had
reduced using six sigma approach.
Six sigma phase by phase
approach from define, measure, analyze, improve and control is to ensure that
variation quality characteristic of the product is reduce or bring to target
per customer spec or both.
Six sigma will only meaningful
in a process improvement if useful data are collected diligently with big
enough sample size to study the current trend and make a statistical conclusion
on the population behavior. Data
collection could focus on one or at the most two parameters which are critical
to quality identified through mapping customer requirement. After improvement, data is collected again and
analyzed statistically to ensure the trend had improved for overall
population. Therefore it is very
statistical based tactical tools to achieve customer requirement be on
objective specification of certain critical quality metric and we must be able
to measure the quality metric.
Do refer to this video for more details
