Re: SIP is not Takt Time

"Mary Poppendieck <[email protected]>" <[email protected]> Sat, 08 Feb 2003 16:06:44 -0000
Newsgroups gmane.comp.programming.software-in-process
Message-ID <[email protected]>
Dossy,
I agree, takt time is the goal, not the actual time.  Say you want 
100 cars to roll off your line in an 10 hour day, that means that 
they need to roll off at the rate of 10 per hour or one every six 
minutes.  So six minutes is the desired takt time.  I reluctantly 
concede that the actual rate at which cars are rolling off the line 
(say one every 7 minutes) can be called cycle time.  By whatever 
name, this time is not a duration, it is a rate.

What I think about, however, is not how many stories per week (or 
whatever) a team can complete, I worry about how long it takes a 
story, once articulated, takes to get finished.  This time – 
whatever we call it – is the important time for SIP.  I used to call 
this cycle time, now I call it service time, some people call it 
lead time.  Basically it is the time from when something goes into a 
queue until the time it comes out.  It is a duration, not a rate. I 
don't think we have a word for the target of this time – but I 
surely could be wrong. 

Mary Poppendieck

--- In [email protected], Dossy <dossy@p...> wrote:
> On 2003.02.08, Mary Poppendieck <mary@p...> <mary@p...> wrote:
> > I have decided to use the term *service time* to refer to the 
time-
> > in-queue definition of cycle time and takt time to refer to the 
line-
> > balancing use of the term cycle time.   
> 
> It was pretty clear to me that takt time, being a goal, is what the
> cycle time needs to be in order for supply to meet demand.
> 
> I can say, "in order to get to work in the morning, I need to 
drive 26
> miles."  This is takt time -- it's the desired goal.
> 
> Now, suppose in the morning I have to run to the post office and 
drop
> off a letter, and stop at the gas station and get gas.  This adds a
> whole 2 miles to my commute.  For that morning, it took me 28 
miles to
> get to work.  This is the cycle time for that morning's commute.
> 
> Am I all washed up here?
> 
> -- Dossy
> 
> -- 
> Dossy Shiobara                       mail: dossy@p... 
> Panoptic Computer Network             web: 
http://www.panoptic.com/ 
>   "He realized the fastest way to change is to laugh at your own
>     folly -- then you can let go and quickly move on." (p. 70)


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