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

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

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

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

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

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

[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

[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

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

[QUOTE=VT-IE;243619]

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

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

[QUOTE=Umang Vidyarthi;243624]


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

What if you were investigating your lead time and you were examining the "time in system"? Correct me if I'm wrong, but when doing a value stream map you use the sum of the cycle time in each process to calculate a total cycle time, then later use that number to determine lead time(add total cycle time to time the WIP spends in the system between processes). It could have an impact there, but its probably not significant. Can you see my confusion?

Thanks,
Andy

[QUOTE=Geoff Withnell;243654]

What if you were investigating your lead time and you were examining the "time in system"? Correct me if I'm wrong, but when doing a value stream map you use the sum of the cycle time in each process to calculate a total cycle time, then later use that number to determine lead time(add total cycle time to time the WIP spends in the system between processes). It could have an impact there, but its probably not significant. Can you see my confusion?

Thanks,
Andy

Sure, cycle time and lead time are different requirements. Lead time = time to first piece (equal to time wip spends in system) + (n-1) x cycle time. Think of a line that takes 2 hours ofor a piece to traverse (wip time in process) with a cycle time of 1 minute, as I defined above. Then the lead time for 100 pieces would be 120 minutes (to get the first piece) + 99 minutes (to get the rest of the lot) or 3 hours 39 minutes.

Geoff Withnell

[QUOTE=Umang Vidyarthi;243624]


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

The main point raised here is, whether the definition of cycle time given- "The time interval between start and finish of an operation"- is correct or not.

2.Time consumed on the assembly line is covered in 'Total cycle time'.

3.For making 6 pcs only, I will not prefer to load it on a 6 position rotary table machining center.

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

IMHO "Rate of production" relates to 'Number of units produced per minute', which in turn relates to cycle time and not to Takt time as you have suggested. There is a popular mis-concept about the Takt time, which in fact is taken as "Minutes per Unit" and not as "Units per Minute.

2.The concept of 'customer demand' is absolutely correct while catering for a single customer. In case of multiple customers, one has to consider 'Total demand' (of course of the customers). This terminology also covers the after market demand. Obviously, in the days of 'Lean manufacturing' & 'Zero inventory' ideology, no one wishes to produce without a demand! IMO, 'Total demand' is the controlling word, since the customer is automatically behind the demand! Therefore Takt is focused on 'Demand' - created by customer(s) and/or market.

:topic:

'TAKT' is a German word for the 'Baton' used by orchestra conductors to make the musicians play in unison.

Umang :D

IMHO "Rate of production" relates to 'Number of units produced per minute', which in turn relates to cycle time and not to Takt time as you have suggested. There is a popular mis-concept about the Takt time, which in fact is taken as "Minutes per Unit" and not as "Units per Minute.

Umang :D


I think you took the paragraph out of context regarding my statement about "rate of production". My comment about rate of production was directed at your equation and then description of takt for the variable "T". At some point though, once takt has been determined, then essentially this does become the desired "rate of production" off a line, workcell, etc. From this perspective:

Takt = rate of customer demand = rate of production to satisfy customer demand

It all starts to fuse together at some point and turns into an exercise of semantics. Whether or not the cycle time can meet takt is a different story altogether. In those instances it is time to look at alternative methods to align with takt.

Wayne

I've got a question about cycle time. When takt time is calculated out and also the cycle time for each process, to plot it up to identify the bottleneck, how should I capture the cycle time for that plot? Is it from the ideal machine running rate or from the real operation output rate?

In the case of real operation output rate, should I uses an output per day devided by the available time per day which is included in all the downtime or should I use only the uptime of each operation?

Thank you =)

I've got a question about cycle time. When takt time is calculated out and also the cycle time for each process, to plot it up to identify the bottleneck, how should I capture the cycle time for that plot? Is it from the ideal machine running rate or from the real operation output rate?

In the case of real operation output rate, should I uses an output per day devided by the available time per day which is included in all the downtime or should I use only the uptime of each operation?

Thank you =)

Always use real times. You could put an additional line showing where the theoretical rate is supposed to be, but it is always better to focus on reality versus what was stated in the sales pitch.

The actual output should in the same unit as takt time. Takt time is typically expressed in seconds, and so the cycle time (c/t) should be as well. Example for a linear assembly line of three stations:

--------------Takt---c/t
Station 1----10------8
Station 2----10-----12
Station 3----10------9

The problem station is #2. You could try to take two seconds from station #2 and shift it to station #1, or move one second of work to both stations #1 and #3. The preferred option would be to reduce station #2 to eight or nine seconds for better flow, but still produce at the 10 second takt.

Wayne

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
--------------------------------------------------------

I am really confusing about lead time and total cycle time

0. Total cycle time = sum of all cycle time from every station?

1. As you define the toal time interval between start and finish of all operations. Does it mean that it includes material waiting time between stations.

2. What is different between the total cycle time and Lead time?

3. In the Little law, what kind of time do you use? cycle time or lead time?


4. How do you think about below formula:

Cycle time = (Value Added time + Non Value Added time) at one station

Lead time = Cycle time + material waiting time

--------------------------------------------------------

I am really confusing about lead time and total cycle time



Lead time would encompass the entire value stream: material lead times, total manufacturing time, transportation times, etc.

Total cycle time would be restricted to the sum of just those elements in manufacturing.

For a more concrete variations, I would reference the APICS' (Association of Operations Management) dictionary (http://www.apics.org).

Wayne

Lead time would encompass the entire value stream: material lead times, total manufacturing time, transportation times, etc.

Total cycle time would be restricted to the sum of just those elements in manufacturing.

For a more concrete variations, I would reference the APICS' (Association of Operations Management) dictionary (http://www.apics.org).

Wayne
------

Thank Wayne

I am clear now

For lead time calculation. I assume a case as follows:

Station1 (2h) Station 2 (10h) Station 4 (2h)
Station 3 (2h)

Parts from station 1 will go to Station 2 and 3 for processing. Station 2 & 3 are parallel to each other. after Station 2 & 3 it all come to gether to assemble in station 4. station cycle time is assumed as in bracket

Total cycle time = 2+10+2+2 = 16 hr

Lead time = 2+ 10 + 2 = 12 hr (the longest path)

is my understanding correct? please advise

Thank you in advance:agree1::agree:

Chomvn

------

Thank Wayne

I am clear now

For lead time calculation. I assume a case as follows:

Station1 (2h) Station 2 (10h) Station 4 (2h)
Station 3 (2h)

Parts from station 1 will go to Station 2 and 3 for processing. Station 2 & 3 are parallel to each other. after Station 2 & 3 it all come to gether to assemble in station 4. station cycle time is assumed as in bracket

Total cycle time = 2+10+2+2 = 16 hr

Lead time = 2+ 10 + 2 = 12 hr (the longest path)

is my understanding correct? please advise

Thank you in advance:agree1::agree:

Chomvn

Actually, if processes are in parallel, I would say the cycle time is 14 hours (the time it takes for a unit from start to finish). The TOTAL # of labor hours to produce a unit would be 16 hours, but you would still be getting a unit off the line every 14 hours.

Your lead time to the customer could be 14 hours, but that's making the assumption that no additional time is required for packing and transportation to the customer.

The interesting thing about all this is that there are lot of different ways to look at it, and nuances that can be introduced. What is especially important is that you are consistent, and that the methodology is understood internally and by the customers.

Wayne