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The quick comparison we at the Artige Company always like to use is that the difference between takt time and cycle time is the same as the difference between the physical properties of period and rate. In a sense these two terms are talking about the same concept, that being the execution of tasks, and how long it takes to execute the task at hand, whether it is the creation of an object or the delivery of a service. The physical units between the two definitions are different, where rate is given in units per time interval, while period is just a time interval. That is because there is a difference in the particulars that are being measured. A period looks at how long it takes to run through one cycle of executing a task. Rate looks at how many execution cycles take place over a given time. |
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This difference in the definitions points out that there is a difference in perspective of the various people handling process design and its subsequent operation. As we have pointed out in our BPDA article, the different perspectives are due to the responsible people being measured by different criteria. In the same organization, many people will be responsible for the same process, and those people will each have their own set of criteria to meet. Therefore, these sets of criteria will need to be met simultaneously. Now when one group sets off to satisfy its criteria, it is quite possible that another group's criteria will not be met, unless there is synchronization done between these groups. Now one can see where the business component of process design will enter into the comparison between cycle time and takt time. It is the business enterprise that sets the criteria, not the laws of physics. So this analysis will now elucidate upon the definitions in terms of meeting the sets of criteria set by the business. |
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As was noted above, both cycle time and takt time measure pretty much the same thing, just that there is a different focus for each term. It is this focus that the process designer is concerned with. The definition for cycle time noted the terms "interval of time" and "recurring". Cycle time refers to the amount of time it take to make a unit, which is what the "interval of time" referred to. The item being made, or the service to be delivered is to be done so more than once, which is what the word "recurring" referred to. What is interesting about this definition is that while there is a desire to repeat the task, the focus is on a single one task, only on one unit. |
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The definition for Takt time noted the terms "rhythm" and "produced in". Takt time refers to the fact that the task will be performed at some given rate. This instinctively advises the reader that Takt time also refers to a repetitive task. The phrase "produced in" alludes to management and direction, that the rhythm is not necessarily natural, but deterministic. One reason that the phrase Takt time is used in the context of process design, is that it brings up visions of a musical conductor, the person that leads the orchestra of production, who is a leader that takes into account all resources available and makes beautiful music. So happens that the German translation of a baton is "Taktstock", which could be literally translated back into English as "beat stick". This should emphasis the connection of takt to rhythm and a beat. |
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The previous paragraphs have set up the scenario to explain the difference between cycle time and takt time in a business process design context. Takt time requires one to consider an entire enterprise when designing a process, while cycle time would have one concentrate on just the task at hand, whatever it takes to make a unit in as short a time as possible. This comparison can be extrapolated a bit using concepts from physics. Even though cycle time has the word cycle in it, it typically focuses only on the "up" side of the cycle, where the item is being made. It essentially ignores the "down" side of the cycle, which can be idle time, the preparation for the next cycle to take place. Takt time would consider both the "up" and "down" sides of the production cycle. What this does is provide the practitioner with an expectation as to how the process should behave. It brings predictability into the design effort. |
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Taking the conductor concept that Takt time brings further along, a business process that is designed to include Takt time will be designed to operate at a steady rate, with no surprises desired. That is the benefit that predictability provides. In order to do this, a process designed with a Takt time would require one to consider the entire production line, as one is concerned not only for the outcome of one system or workstation, but how they all interact with each other. The ramification of setting a certain rate needs to be resolved amongst the various steps and systems of the process. One can see at this point that a variable production rate would make for a difficult task in resolving the system components with each other. That is not to say it would be impossible, but the resources required to design and operate a variable rate process will be greater than that of a process operating a steady rate. |
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Finally, there is another temporal term that one might come across when designing a business process, that being TAT, or turn around time. This is another cyclic term that considers only one unit of production. TAT is the time from notification to create a product, to the point in time when the product is delivered. It identifies a period, and has units of time. This term is construed to have different meanings for different people and different organizations. This difference in meaning has to do with where everyone considers the start and end points to lie. Some organizations may consider the start point to be the receipt of an order from a customer. Others may consider it to be the initiation of a work order. As you can imagine, these permutations are endless. For this analysis it is enough to understand that TAT is related to the period of time required to create one product. As such, it is not directly a part of a business process design effort that is working on meeting a specific Takt time goal. However, one can always measure TAT, regardless whether any Takt time or cycle time design parameters were considered. |
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Here is an example to show why Takt time is not a suitable parameter for evaluate TAT. The term Turn Around Time is used in the airline industry to describe the amount of time it takes to process a plane between the time it has arrived at the gate in an airport and when the plane is ready to accept new passengers. This process involves many steps, some of which can vary widely in time from one instance to the next, depending upon specific passenger needs, maintenance items, or unexpected environmental matters. One would not claim that the Takt time of an airplane turnaround is one every 20 minutes. That would mean there would be another plane to turnaround immediately after the first plane was completed. It may be possible to say that a work crew that can work two planes an hour, or a gate can handle six flights a day. So, what is missing in TAT tasks is the rhythm and predictability that Takt time is channeling and then exposing, which is why TAT tasks are not effectively measured by Takt time. |
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| Conclusion |
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This article provided definitions for cycle time and takt time, both at a pure physical context and at a business process design context. The difference promoted by the popular business press is that in one scenario (takt time) we take the whole picture into concern, in order to produce most items with least resources in a total aspect. The other way (cycle time) we only consider what it takes to make one unit, without regard for the entire process. So it is possible that with cycle time one can start off quick, but might slow down later if a supply line is starved because the production rate is running too fast. Or maybe some items can be made quickly, but others are slow, and the unevenness makes problems for the entire line. Takt time works on the promise that a steady period is predictable, and people can handle predictable situations better than unpredictable, unstable periods. |
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This difference is driven by the fact that there are multiple sets of criteria that need to be met simultaneously when designing a business process. Some organizations allow one to consider only cycle time, while other organizations demand a thorough design consideration that a Takt time approach should provide. Interesting how criteria can drive one's perspective. |
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| Questions |
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1- Is it possible for takt time to be greater than cycle time? |
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This question is helpful in that it brings up another way to compare takt time to cycle time. Consider that a process can run within an average period of time, in that there is an expected period with deviations that will be quicker or slower than the expected period. That is essentially what the takt time would be based upon, the average cycle time. Except that one will aim for a period that is longer than the average, not the mean itself. One scientific measure for the takt time would be to use the upper control limit of the process cycle time. While the slack time established by employing the upper control limit is wasteful in itself, the purpose of takt time is to set a rhythm in order to deploy resources in a predictable and controlled manner. This is a preventative tactic to reduce waste from accumulating errors as the process runs, and acknowledges the tradeoff between some purposeful waste in order to prevent unexpected major waste otherwise. |
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The converse question is important too, is it possible for cycle time to be greater than takt time? That is essentially what we are trying to prevent above when we use the upper control limit as the takt time period. Consider what if we used the lower limit instead? Then the process will eventually fail, as we have not provided enough time for multiple cycles to run to completion. By eliminating all slack and then some, we have set up a situation that is the complete opposite that takt time was to afford. A takt time less than the cycle time would result in discord instead of harmony. |
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2- Why would I want to run a process under takt time? |
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Here is a practical non-manufacturing example of takt time that many people can relate to. Say in Germany, one might come across the following phrase at a bus stop notice board: "Die Linien 38, 40 und 41 fahren jeweils im 10-Minuten-Takt". Translated it says "Bus lines 38, 40 and 41 each will run at a 10-minute-takt". From above we learnt that takt in this case relates to the rate of the appearance of busses. We present the German phrase to make the point that the word "takt" is commonplace in the German language in the context we are taking into account here. Consider now the experience that some bus riders have had, where a bus runs late, and then the next scheduled bus appears immediately after the late bus. Here we have a process failure that not only failed to meet an obligation of picking up one set of passengers in a timely manner, but can also cause subsequent stages to fail, where the initial late bus could cause the subsequent bus to become late. |
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So what does this example of a bus running every ten minutes tell us? The main point is that an average rate is not a sufficient criterion to run a process on. A ten-minute takt would average out to a rate of six busses every hour. Yet, if all of the scheduled six busses appeared at the top of the hour, then people requiring a ride at other points of the hour would not find the service to be of much value. In addition, resources may be wasted, if one or two busses collected all riders at the top of the hour, leaving four busses running empty. For those riders expecting to make connections to ongoing busses, they may become further disappointed. The same goes for manufacturing lines. Late delivery of pieces will force downline processing to be held up. In the case of bus services, following a takt or rhythm will be more valuable to bus riders than just making sure the busses finally show up sometime in the hour. Deviations away from the takt time would be considered a process failure and a loss of quality. |
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As an aside, we found another example of Takt usage in German, as evidenced by the following example: "Die Kaehne knartzten im Takt der Wellen". Translated means: "The barges groaned in time with the waves", or as we now know how to translate: "The barges groaned in the Takt time of the waves" As you can see, the term Takt can be applied to any situation where there is a cyclical process underway. |
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3- How would you deploy takt time in a service organization? |
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This is an excellent question, as it raises points about what it means to run a service-based business, plus allows us to explain why takt time implementations in real-time systems seems to be a paradox. It should be apparent in the previous explanations for takt time that it is a deterministic factor. When one designs a process, one will purposefully set it up so that there is sufficient time to carry out all tasks, and done so in a manner that the tasks are carried out in a predictable manner, allowing for a harmonious resource consumption and communication of process information. That is fine in a manufacturing setting where one typically has control over the environment and production aspects. |
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On the other hand, service businesses are not typically operated in regulated environments, and are subject to the whims of the consumer and the facilities of the suppliers. The main differentiator from a manufacturing business is that demand can change dramatically in real time for a service business. The manufacturer typically has practices that allow for slack and storage, allowing the manufacturing business to deal with fluctuations in demand, but at an additional cost. It is difficult for a service provider to deploy those same slack-oriented practices when faced with fluctuating demand, especially in the delivery of the end product. Imagine the consumer tapping their shoe as they wait for your next batch of bank deposits to be processed. That customer will walk out on you, and your service business would suffer. |
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What the service industry is being subjected to is pull demand. The requests for end products are typically done in real-time, without warning. When demand is unpredictable, one will be hard pressed to use a deterministic process when running the business. One example of a deterministic process is takt time. In order to run a process under takt time, one must know how many units are being produced and how long it takes to produce each unit at a comfortable rate. With orders being accepted in bunches and then long periods occur between orders, it will be difficult to predict when the next cycle would be run, which is not deterministic. Takt time will not be an effective tool for a service business. |
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The manufacturing industry typically operates in a push demand environment, where the manufacturing firm predicts or calculates the demand for its products, and then sets its own schedule to its own advantage. This is a deterministic approach, which most people can deal with, as it minimizes as much surprise as possible. With the lack of surprise, one can set up a predictable cycle and run a harmonious production, and one can even do so at a comfortable takt time. |
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Now there are instances where a service industry may trade off some unexpected demand against customer satisfaction, therefore market share, by forecasting delivery of end product and creating to inventory. This is an instance where the service business is trying to move away from a pull demand scenario. In any process that is done in a deterministic manner, one can then deploy a takt time approach. However, factors such as freshness and timeliness may come into play, where one is unable to create to inventory. It is curious that manufacturing businesses are trying to move towards a pull demand environment, even if their products are not sold as such. Reason for that is to reduce costs by reducing slack. For both service and manufacturing businesses, it all comes down to the need to have a process in place that can work with as little slack and waste as possible, plus be as fast as possible (minimum cycle time). Basically one requires a process that can deliver end products in real-time, and the point of takt time becomes moot. |
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We have added two Takt time business cases, both in the service industry. They provide additional insight into service industry operation, in both a push and pull demand environment. |
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4- Can takt time be variable? |
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The quick answer to this question is NO! Depending on how one views their process, the answer could be, perhaps. As explained above and referencing our BPDA article, purposefully setting up a process with variable parameters will result in a situation where predictability is reduced, and that is not conducive to operating a process for maximum production with minimal resource consumption. A process set up to operate under takt time needs to have as many unknowns removed as possible, so the process can operate in a harmonious environment. This means variability must be reduced for successful takt time operation. |
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The maybe comes into play when we consider the secondary level process design. It may be desirable, or even necessary, to operate the process at different takt times, as the production schedule is executed. The extreme case is a factory that runs only one shift every day, say from 8 AM until 4 PM Monday through Friday. The takt time in this case is a step function, where it has some value during working hours, and then drops to zero during none working hours. Other production situations can arise, such as trimming takt time as labor becomes available and increasing takt time as labor is called away. These scenarios rely upon slack to trade off production for resource availability. |
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So, when answering this questioning one needs to consider the context of first level or second level process design. The answer for the question of "can takt time be variable" on the primary process design level is NO, and secondary process design level is YES. |
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Another twist to this question comes from the viewpoint of a Turn Around Time (TAT) task. As explained earlier, a TAT task is a single execution of a cycle and may be recurring. The difference between TAT and cycle time is that in a cycle, the recurring actions are fully expected to occur one right after another. A TAT task may be performed immediately after the first one, or there may be a lag of minutes, hours, even days, dependent upon demand. Frequently a TAT task is a service task, and there is an expectation that the task is performed frequently. What is lacking is a guarantee of demand, when the next task will be needed. In addition, the tasks can vary widely, dependent upon the specific needs of the task at hand. This last feature of a task is why one would wonder if Takt time can be variable, as that would be necessary for a variable task. At this point a different parameter would be needed to describe such an attribute, as Takt time is definitely a desire for predictability. |
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