Takt Time vs. Cycle Time vs. Total Cycle Time

tomccchang

Involved In Discussions
#1
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

Quite Involved in Discussions
#2
Re: Takt Time vs Cycle Time vs Total Cycle Time

tomccchang said:
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
 
V

VT-IE

#3
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

Inactive Registered Visitor
#4
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
 
U

Umang Vidyarthi

#5
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 :D
 
V

VT-IE

#6
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
 
V

VT-IE

#7
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
 
U

Umang Vidyarthi

#8
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'. :nope:

Geof may wish to opine on this.

Umang
 

Geoff Withnell

Inactive Registered Visitor
#9
Hello Andy,

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

Geof may wish to opine on this.

Umang

If ylou are looking at an ongoing process, the length of time a unit spends in processing is usually not an issue. Think of an automotive assembly line. Each vehicle may spend several hours moving down the line, but the line's "cycle time" is usually thought of as how frequently a finished vehicle comes off the end of the line. On the other hand, if one is considering a 6 position rotary table machining center, and you only run 6 pieces, the cycle time would include the time from when you loaded the first piece on, until the time you unloaded the sixth piece, which would be significantly different.

Geoff Withnell
 

wmarhel

Quite Involved in Discussions
#10
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

Umang :D
Umang,

Takt time is solely the rate of production required to meet customer demand. While your equation is technically correct, your definition of it, "minutes of work per unit produced" is incomplete. The ideal scenario would be for takt and cycle time to be equal, but this rarely the case. Cycle time is often slower or faster so adjustments would need to be made. A better definitition would perhaps be "target rate of production". Your definition as stated would basically be the same as that for cycle time.

I would also clarify the equation to support takt to be customer demand and not "total demand". If my customer only wants 100 pieces/day, but I choose to make 150, then theoretically my takt is based on 100/day. From a capacity and/or planning standpoint, I may be looking at increased demand in the near future and wish to employ some other method such as level loading in order to alleviate the need for overtime. But that doesn't change the fact that takt is customer focused.

Please don't think I'm nitpicking, I'm just trying to present the perspective based on the "purist" approach since that is what most people will have been taught or read versus what one company may or may not do. What it really comes down to is what may work for one company doesn't necessarily guarantee success for another.

Wayne
 

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