#9 Takt time, Cycle time, Processing time 구별하기 - Defining the different times

In this section, we will discuss what is the definition of different 'Times' which are commonly used in the Lean and Quality world.

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Let's explore the definition of the different times as below.

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- Takt time: Takt time is the rate at which you need to complete the production process in order to meet the customer demand.

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· Takt Time(TT) = Net production time (per shift)/ The number of customer orders (per shift)

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*The Net Production Time (NPT) is the clean time your team has at their disposal to finish a product. To calculate your NPT, you can subtract the time your team spends on downtime (lunch breaks, other breaks, meetings, machine maintenance…) from the total time your team spends at work.

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- Cycle time: Cycle time is the time it takes to complete the production of one unit from start to finish. Takt time is based on customer demand whereas cycle time is work process-based.

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· Cycle time(CT) = Gross production time / number of units produced

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*Gross Production Time (GPT): correspond to the time during which the line is occupied with some type of activity (i.e. Production or Downtime) or it is not physically capable of production

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- Processing time: Processing time is the time that product spends on a workstation or a cell.

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· Processing time(PT) = Net production time / number of units produced

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- Throughput time: Throughput time is the sum of the following times, processing time, waiting time, and moving time. Throughput is the rate at which items, which can be a lot of times, are passing through the system.

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- Lead time: Lead time is the time it takes for one unit to make its way through your operation from front to end (from taking the order to receiving payment).

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- Changeover time: Changeover time is defined as the time elapsed from the last good part of the previous run to the first good part of the following run. The important part of the definition is the qualifier “good,” because a successful changeover is not complete until the new part run is meeting quality standards.

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With the above definition of different times, still, many of you might be wondering what is different between the times. Here you can find some illustrative examples to elaborate them more in detail.

[Takt Time VS Cycle Time]

The red line on top is the Takt time showing where the customer needs are, which means the Voice Of the Customer(VOC). Maximum allowable Cycle Time with a green line explains the organization's control limit, which can be the Critical to Quality Requirement(CTQ). You can refer to the previous section linked below for VOC and CTQ. 

​#4 고객의 니즈(Needs) 파악하기 Part 1 - Understanding Your Customer

#4 고객의 니즈(Needs) 파악하기 Part 1 - Understanding Your Customers' Needs

 

As the actual Cycle time includes the Downtime, Changeover time, and Rework time, it is generally much bigger than the Processing time.

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Then let's try to find the pictures of the Lead time, Throughput time, and Cycle time in the below figure. As the Lead time includes the order receiving step, it takes a bigger scale of the timeline than Throughput time. Throughput time is measured from the physical starting point of a process to a physical ending point, whereas cycle time is measured from the start of a process to the start of the next cycle of that process.

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[Lead Time VS Throughput Time VS Cycle Time]

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Considering productivity and efficiency, designing the process flow at the workshop floor is critical. As we understand the formula about Processing Time and Cycle Time, we can assume how much dead time and/or non-value-added time consumed in 'No organized and no controlled' process flow compared to well-organized and controlled flow. Let's give a glance at the two different layouts in the below figure.

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[The different workflow between Non organized layout and U-shape cell]

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Real Story] This is a story about 'Changeover time' innovation done in the Toyota Production System.

In traditional mass production, the first thing the setup teams did when they performed the changeover of a production line from one model to another was to shut down the press. Shigeo Shingo wondered how much of the changeover he could perform while the press was still running, so he organized an operator's workplace for that purpose and made other technical improvements until there was no more setup the operator could do while the press was running. Things like getting the next die and tools, preheating the die, and setting it in place beside the press were external and could be done while the press was making parts. When he finally shut down the press, all that was left to do was basically to swap the dies and start it up again. Amazingly, these several-hundred-ton presses that previously took many hours to change over could it turned out, be changed over in minutes. Think of it like a racing pit crew that quickly services and gets the car back on the track, often in less than a minute.

 

 

※ 참조: 본문은 책, "Dummy들을 위한 린 식스시그마(Lean Six Sigma)"와 The Toyota way를 정리한 내용을 기반으로 제 경험들을 조미한 글입니다. 현재는 원서 기반으로 내용을 정리하고 있는 중이며, 정리가 완료되면 한글로 번역을 추가할 예정입니다.