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Takt-time refers to ideal timing for production of given parts in relation to the customer requests. If takt-time is respected during work, then the necessary quantity of stock will have been produced. This goes for internal and external customers alike.
This is the first data needed for just-in-time production. Generally, takt-time of the most bottlenecked machine will determine the rhythm of an entire production line. It’s important to work on it: this variable is like the tempo given by the conductor.