Page 89 - How To Implement Lean Manufacturing

70 Cha pte r F o u r

sometimes One Touch Exchange of Dies (OTED). In his writing, Ohno refers to three
basic elements of JIT. They are pull systems, operating at takt time with continuous flow.
Those may be the big three but JIT is seldom practical without some application of
SMED technology. It is a major batch destruction technique. The basic procedure of
SMED is simple, it is a three-stage process:

1. Separate internal from external setup
2. Convert internal setup to external setup
3. Streamline all aspects of the setup operation
When a SMED application is first undertaken, we have found the best tool is the
simple Gantt chart, showing all the steps in the changeover. Gather the knowledgeable
people on the changeover, and then list all the changeover steps. Categorize them as
internal setup, external setup, or internal but can be external; also list the conditions to
make it external setup.
This is the basic starting point. From here you delete any unnecessary steps and
simplify any steps you can. Next, you convert as much internal setup into external
setup so it can be done with the machine running. With only internal work left, the
technique is generally to create as many parallel paths as possible. At this point, you can
get involved with intermediate and holding jigs, automatic adjustments, and a huge
volume of imaginative approaches to shorten the changeover time.
SMED and poka-yokes are two of the Lean techniques that are truly for the imagina-
tive. This combination is a powerful set of tools to use as we reduce lead times and more
fully utilize our processing equipment,
Much has been made of making a video of a changeover. I support this and have
found it to be useful, but generally it is best to do it after you have applied SMED tech-
niques at least once. The reason is this: When you apply SMED, the entire process will
change, so it is not very worthwhile to view the old process. You will get some minor
improvement ideas, but the majority of the ideas come from the development of the
Gantt chart referred to earlier. However, there is one large benefit to be gained from
making a video: Watching the old technique is usually humbling if not downright
funny, and feeling a little humility as well as a good laugh are both good for the soul. At
any rate, doing a video is easier than it used to be, so I do not discourage it completely.
The application of SMED technology is a key batch destruction technique and
should not be underestimated in terms of its potential. It is one of the major efforts that
must be undertaken if Lean is your objective. For further study, I suggest you go directly
to the author of the tactic, Shigeo Shingo. He has written two major books. One is A
Revolution in Manufacturing: The SMED System, (Productivity Press, 1985), his landmark
book on the topic. In his other book, A Study of the Toyota Production System, (Productivity
Press, 1989), he expanded his coverage on parts of his SMED system. He has refined his
three stages into eight techniques. It is good reading for the Lean professional.

Cycle, Buffer, and Safety Stocks Cycle, Buffer, and Safety Stocks is the three-fold
approach to inventory management used in Lean Manufacturing. Each of the three
types of stock is calculated and marked separately. The common way to separate the
stocks is to use color-coded kanban. For example, white cards are used for cycle, yellow
for buffer, and orange for safety stocks. Red is normally reserved for emergency runs.
Consequently, when a colored kanban shows up at the heijunka board, the production