## Takt Time: Let’s Do Somebody’s Homework

On the back end of this site, I see the search terms that landed people here. This one showed up yesterday:

"a packaging process works two, 8 hour shifts per day. there are two 15 minutes breaks per shift. daily production requirements are 240 packed units, with a planned machine down time of 30 mins per shift, team has to work 60 mins overtime per shift, it is a 4 member team – calculate takt time"

OK, readers, let’s help him out. What’s the answer?

Why is this phrasing ambiguous if the author of the question is looking for a “right” answer?

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## Comments 9

Is it 240 in 8 hours or 9 hours? Exclude the overtime.

Posted 30 Jan 2014 at 7:22 am ¶If this isn’t a trick question……My math is:

Time available = 480′ per shift, less 30′ breaks and 30′ downtime but with an added 60′ overtime gives a net 480′ available per shift…….. Demand is 120 units per shift…so takt time = 480’/120units = 4’……..

Posted 30 Jan 2014 at 7:22 am ¶um . . . and customer demand is . . . ??

Posted 30 Jan 2014 at 7:37 am ¶The ambiguous thing to me was that I don’t know if the planned machine down time is during the breaks. If it’s not then I also get 4. If it is then I get 4.25. This is fun!

Posted 30 Jan 2014 at 8:27 am ¶I think Ron is onto something that begs the question: what is the purpose of calculating takt time in the first place?

(Plenty of companies do just fine without even knowing what takt time means.)

Posted 30 Jan 2014 at 8:34 am ¶Theoretical or actual takt? Makes a difference! Plus you’re right, Mark, what’s the point? Is it being used for CI activity, or just to go on some sort of management report?

Posted 04 Feb 2014 at 11:37 am ¶Assuming that we are searching only for the mathematical answer and not the philosophical “why”, what is unclear to me is the overtime part. If it is mandatory then they really work 2, 9 hour shifts and not 2 8 hour shifts plus overtime.

Either way my confident answer is 4

Posted 05 Feb 2014 at 8:11 am ¶it simply means its cycle time is more than its takt time, that is why they work overtime, it is either the process is improved to bring the cycle time less than 4′

Posted 25 Feb 2014 at 8:24 am ¶cycle time is 4′ 25″

takt time 4′

I don’t think it says anything about the cycle time, only that they work overtime. We don’t know why they work overtime. They might have stoppages, shortages, or a lot of other possible reasons.

I see:

2 x 8 hours = 16 hours x 60 = 960 minutes total work time.

But there are two 15 minute breaks / shift.

2 x 15 x 2 shifts = 60 minutes

So we have 900 minutes of available time to work.

If we just use THAT, then the takt time would be:

900 available minutes / 240 units of production = 3.75 minutes or 225 seconds.

The question is whether or not we count the planned machine down time as “available minutes” or not. The purists would not consider that in the takt time calculation.

However that leaves us with a theoretical number that is of no value on the shop floor. They *must* work faster if they are going to succeed at the end of the day.

So I would subtract the machine downtime:

900 available minutes – 2 x 30 minutes planned downtime leaves 840 minutes to get the work done.

Now we have a new number:

840 / 240 = 3.5 minutes or 210 seconds.

We are getting closer.

If they set up the day to work to that figure, they will *just barely* be done at the end of the day.

So I’d likely pull some more available time out and put it in my back pocket to buffer issues, and we end up with what has a number of names.

“Actual takt” (vs. “theoretical takt”) has already been mentioned above.

Mike Rother would call this “Planned cycle time”

I have also heard it called “Operational takt time”

And, if you read some older books (pre 90 or so) you see the term “cycle time” used interchangeably for all of these.

We are going to use this number to calculate how many people we need, knowing that if we don’t populate job, we will make up the difference with overtime.

Now… there is a lot more to do. This “test question” was just “Calculate the takt time.”

The ambiguity, in my mind, comes down to whether or not the available time used in that calculation should include the planned machine downtime or not.

I am, by the way, assuming that nobody works during the breaks, and production stops. This is usually the case, but not always. But in test questions like this, it would always be appropriate to exclude break time from available time.

Thus, in a multiple choice test, I would eliminate 960 / 240 = 4 minutes right away.

Thoughts?

Posted 25 Feb 2014 at 9:04 pm ¶## Post a Comment