Benefits
of Takt Time
The
simplicity of the concept belies its extraordinary effects.
Among these are:
Production
Stability- by
limiting overproduction, it stabilizes the system and prevents
buildups of inventory and the subsequent stops and starts.
Workcell
Design- Takt time helps cell designers. In an ideal
workcell, all tasks are balanced, they all require the same time
to execute and that time equals the Takt time. If any operation
requires more than the Takt time, the cell cannot produce at the
necessary rate.
In
the first illustration, below the cell cannot make the necessary
quantity because operation #4 exceeds the Takt time. In the
second chart, the work has been balanced at Takt time or
slightly below. This, however, is not the only way to balance
workcells.
 
Psychological-
immediate feedback of
performance is a powerful motivator. When a workcell team tracks
takt time, they have a heightened awareness of output rates and
potential problems. They attempt to achieve the Takt time on
each cycle and immediately make necessary corrections.
When
Charles Sorensen conceived and built the Willow
Run Bomber plant, he designed it for "A
bomber an hour". He did not say
"nineteen ships per day" or "120 per week."
Sorensen understood the value of steady, repetitive output.
At
one point in planning a subordinate asked Sorensen how they
should schedule such a complex operation. "Cast Iron
Charlie" shot back- "Your
schedule is to build a bomber an hour!". The
result was a very simple and effective scheduling system using broadcast
and kanban. There were no computers in 1940. |
History
of Takt Time
Takt
is a German word which refers to the beat of music.
It can also mean cycle, rhythm or repetition time. Sometimes it
refers to the baton of an orchestra leader.
During
the 1930's, Germany and Japan were part of the Axis and German
engineers helped organize the Japanese aircraft industry. They
used the analogy of a conductor's baton setting rhythm for the
entire orchestra. After the war, Toyota
picked up the word and concept for its Just In Time or Toyota
Production System.
Limitations
of Takt Time
Takt
time is useful for simple cells These are
typical of the workcells at Toyota and what most people think of
when they picture a cell. Such cells have:
Job-shops
and other low-volume, high-variety operations can also use
cellular manufacturing, it's just a bit more complicated.
Takt time has little relevance for these Group
Technology workcells.
Here
we must account for setup times, multiple routings and varied
work times. Mr. Lee's book, "Facilities
and Workplace Design" shows how to do this.
You may download the chapter
on workcells from the upcoming Second Edition
Problems
can result from an unjustified preoccupation with Takt time. Designers
who think only of Takt time may conclude that certain products
cannot use Cellular Manufacturing and their companies lose
the many benefits.
In
other situations, an obsession with Takt time, One Piece flow
and linear cells leads to unsuitable designs. This
can have disastrous results as shown in our page "When
Kaizen Blitzing Replaces Strategy".
Takt
time is a powerful and valuable concept. Like all intellectual
constructs, it has limits. |
