Actual Takt Time is Planned Takt Time, Actually



By Jon Miller | Post Date: September 21, 2008 2:15 PM | Comments: 3

This week I am in the land of takt time: Germany. A banner on a railroad underpass for a local news program advertised "news at 60 minute takt." An 80-year old black-and-white photograph at a local museum had a caption of workers building zeppelin airship parts "at machine takt" paced by mechanical devices, a novelty in those days. I am looking forward to learning perhaps a few more native uses of the word takt which has become a part of the world's lean lexicon from Germany via Japan.

Takt time is a key concept for achieving one of the goals of lean: synchronizing supply with demand to avoid all wastes associated with overproduction. In practice this means calculating the pace of customer demand by dividing the net available time to work for a period by the customer demand for that period. The net available time is independent of the number of resources (people, equipment, etc.) available and represents hours open for business.

There is also something called Actual Takt Time which like many Japanese words and phrases that come from the Toyota Production System, suffers a bit in translation. When one asks "What is the actual takt time?" it may simply be a clarifying question, rather than asking for the Actual Takt Time or "jikko takt time" with a long O (実行タクトタイム) as a Toyota person might refer to it.

We have seen this "actual takt time" term sometimes misused to mean the actual pace at which parts are being produced, or line-off speed. This is not at all Actual Takt Time. That may be called the line speed, production pace, production rate, or simply the varying cycle times from process A to B, but it is not the actual takt time. For example in the book The Elusive Lean Enterprise authors Keith Gilpatrick and Brian Furlong state:

Once you have eliminated your backlog, and have determined what actual Takt Time should be for any period, you should rebalance your lines, or limit the hours of production to meet the actual Takt Times.

In English "Practical Takt Time" or "Executed Takt Time" would be more appropriate translations, since "actual" implies true or pure instead of processed or adjusted, as is the case with Actual Takt Time. In contrast to the true takt time that is calculated from net available time per shift divided by demand per shift, the so-called Actual Takt Time is calculated when one must operated within hours other than the standard working hours. This adjusted takt time that is used to plan production around a period of time other than a standard shift, such as reduced or extended hours, in order to practically deliver a required quantity over that period. Takt Time is calculated strictly from net working time divided by the demand for that period, but Actual Takt Time is calculated by factoring in practical issues that reduce or add to the net available time.

Jon,

Good post. I am going to link to it from the TPM Log today because you have addressed one of the problems I frequently encounter among people who really should know better. I am constantly having to redefine takt time to managers and engineers who mistake it for cycle time and cause much confusion.

Poster: Mike Gardner | Post Date: September 22, 2008 5:11 AM

How do we establish actual tact time when we always have a backlog due to over scheduling in which we have no control of ? Looking for some help.

Poster: michael czerpak | Post Date: August 2, 2009 10:59 AM

Hi Michael

If the over scheduling is because of true customer demand then takt time should be recalculated to include that demand. If capacity is not sufficient, you need to do kaizen to create capacity.

If the over scheduling is for unnecessary goods due to push, the first step is to stop this overproduction. Takt time is almost meaningless without flow and pull, and pull stops overproduction.

If you would like to give me a bit more background I could give you a more in-depth answer.

Poster: Jon Miller | Post Date: August 11, 2009 8:57 AM
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