Takt Time vs. Cycle Time vs. Total Cycle Time

[tomccchang]

I am confused over takt time, cycle time and total cycle time.

For example, if I have 4 steps to complete one signle production item output, and each step takes :

step 1 : 5 sec (hand insertion)
step 2 : 0.8 sec ( SMT )
step 3 : 8 sec ( 3 machines in series, each machine has 2 sec, 8 sec, 5 sec )
step 4 : 2 sec (AOI)

Can I say the cycle time is 8 sec, while the total cycle time is 15.8 sec ( 5+0.8+8+2 ), and takt time is 5/0.8/8/2 for each step ?

Thanks.
Tom

[wmarhel]

Originally Posted by tomccchang

Can I say the cycle time is 8 sec, while the total cycle time is 15.8 sec ( 5+0.8+8+2 ), and takt time is 5/0.8/8/2 for each step ?

Tom

Since your example process has four operations or steps, each operation would have their own "cycle time" or, the time it takes from the start of one piece until the beginning of the next piece.

"Total cycle time" would be the sum of all the process steps or the 15.8 seconds you calculated.

Takt time is the pace required to satisfy customer demand. For example, on a single 8-hour shift you have 480 minutes of available work. Subtract the time for any paid breaks and/or meetings (start of shift, quality, etc.) For this example we'll take two 10-minute breaks and one 10-minute meeting at the beginning of the shift.

This leaves 480 (total shift time in minutes) - 30 (time for two breaks and one meeting) for a total of 450 available minutes per shift.

If the customer places an order for 900 units, and the parts are scheduled to be produced on a single shift, then the takt time is 1 minute.

450 available minutes / 900 units = .5 minutes (30 seconds) per unit.

As long as the processing time is below the takt time, life is good.

Wayne

[VT-IE]

I had this exact same question, thanks for the clarification. But I'd like to take it one step further: Let's say you have a machine that performs overlapping processes within itself(for instance it starts to infeed a new part as it outfeeds a finished part). How do you define the time it takes to complete a part from start to finish? How do you define the time between finished parts coming out of the machine?

Thanks,
Andy

[Geoff Withnell]

Originally Posted by VT-IE

I had this exact same question, thanks for the clarification. But I'd like to take it one step further: Let's say you have a machine that performs overlapping processes within itself(for instance it starts to infeed a new part as it outfeeds a finished part). How do you define the time it takes to complete a part from start to finish? How do you define the time between finished parts coming out of the machine?

Thanks,
Andy

Actually it is not too difficult. Pick some point in the cycle, e.g. when a part clears the machine on the output side. As part 1 reaches this point, start timing. When the 6th part reaches this point, stop timing. Divide elapsed time by 5. This is the cycle time. I measure several cycles to even out rndom variation. How many parts may be in what part of the cycle is really not relevent.

Geoff Withnell

[Umang Vidyarthi]

To sum it up in short:

Takt time : minutes of work per unit produced = T

Available time : Actual available minutes per day/shift =Ta

Total demand : Units required to be produced per day/shift = Td

The Takt time T = Ta / Td

Cycle time : The time interval between start and finish of an operation

Total cycle time : Total time interval between start and finish of all operations.

Umang

[VT-IE]

Originally Posted by Geoff Withnell

Actually it is not too difficult. Pick some point in the cycle, e.g. when a part clears the machine on the output side. As part 1 reaches this point, start timing. When the 6th part reaches this point, stop timing. Divide elapsed time by 5. This is the cycle time. I measure several cycles to even out rndom variation. How many parts may be in what part of the cycle is really not relevent.

Geoff Withnell

Thanks for the reply Geoff. It looks like both companies I've worked for have been using "takt time" and "cycle time" interchangeably.

Thanks,
Andy

[VT-IE]

[QUOTE=Umang Vidyarthi;243589]
Cycle time : The time interval between start and finish of an operation/QUOTE]

If there is some overlap in an operation then your definition of "cycle time" may be flawed. For instance, each part may spend 20 seconds in the operation, but because the input and output of the parts are overlapping, a finished part may roll off the end of the operation every 15 seconds.

This is really all semantics, but I'd still like to get my vocabulary corrected.

Thanks,
Andy

[Umang Vidyarthi]

[QUOTE=VT-IE;243619]

Originally Posted by Umang Vidyarthi

Cycle time : The time interval between start and finish of an operation/QUOTE]

If there is some overlap in an operation then your definition of "cycle time" may be flawed. For instance, each part may spend 20 seconds in the operation, but because the input and output of the parts are overlapping, a finished part may roll off the end of the operation every 15 seconds.

This is really all semantics, but I'd still like to get my vocabulary corrected.

Thanks,
Andy

Hello Andy,

IMO overlapping does not influence the 'cycle time'. The difference due to overlap is recognised in the 'Total cycle time'.

Geof may wish to opine on this.

Umang