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.
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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.
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