TAKT time is the time available to make one product or service. It is a design parameter that is used in lean deployment to design the process – for example to determine the number of people that should be working in a process.
Let’s say that we have to satisfy 10 orders in a day. The working day consists of an 8 hour shift with about 1 hour for breaks and 2 hours lost for meetings and other non-value added activities. Hence, we need to satisfy 10 orders in 5 hours. This implies that we have roughly 2 orders to complete in 1 hour. Hence, the TAKT time is 30 minutes. This means that on an average, we receive one order every 30 minutes. If our cycle time (time taken to process one order) is less than the TAKT time, then we say that our process is capable of meeting the customer demand. If our cycle time is greater than the TAKT time, then we state that our process is not capable of meeting the customer demand. This would be a bottleneck in the process.
TAKT time is a calculated parameter that depends on the available time and demand. The formula for TAKT time is: (Available Time per period)/(Demand in that period). The units for TAKT time is time as measured in an appropriate unit such as minutes, hours, days etc.
TAKT Time for Multiple Products
Let’s say that we have 2 products that are manufactured on the same line. Product A has a demand of 100 units per month and product B has a demand of 60 units per month. Hence, the total demand is 160 units. In a month, if we have 20 working days with each day having 8 hours. Then, the TAKT time is 1 hour. If the cycle time for product A is 2 hours and cycle time for product B is 0.5 hours. Is this process capable of meeting customer demand?
In this case, the weighted average cycle time would be (100*2 + 60*0.5)/160 = 1.4375 hours. Since, this is larger than the TAKT time of 1 hour we would say that this process is not capable of meeting the customer demand.
TAKT Time vs. Cycle Time
Cycle time is the time it actually takes to perform the process or activity. It usually does not include waiting. Cycle time is a measured parameter and depends on the process steps, the person performing the process, time of the day, efficiency of the person etc. For some processes, the cycle time may be a fixed number such as 10 seconds to print a page while for other processes, where some manual element is involved, the cycle time may be variable, so we usually report the cycle time within a range, say the order entry takes between 4 minutes to 15 minutes depending on the type of order being processed.
The cycle time also depends on the batch size – how many of the products we are working at the same time. It is the average time to perform one job. So, if you are working on two things at the same time for 2 hours, then the cycle time would be 1 hour (for each job on average).
Hence, TAKT time would be a calculated value and the cycle time would be a measured value.
We can create a chart that compares the cycle time and TAKT time. This chart plots the overall TAKT time for the process and the cycle time for each step. As long as the cycle time is less than the TAKT time for each step, we say that the process is capable. If a particular step is not capable, we call that step as the bottleneck. In order to resolve bottlenecks, we can redistribute the work from that step to other steps in the process. This process of leveling out the work to ensure that each step in the process has similar amount of work is called workload balancing. Workload balancing enables the process to meet customer demand, improves the morale of the people working in the process and enables an improvement in the productivity and efficiency of the process.
Handling Changes in Demand or TAKT Time
If the demand changes, then clearly the TAKT time also changes. A process that may have been initially capable may no longer be capable if the TAKT time suddenly drops. How do we handle this change in the TAKT time?
We need to have a process in place to adjust to changing TAKT times. If the TAKT time is higher, then we have more capacity compared to demand. The capacity could be lowered by either running less number of shifts, reducing the workforce (use less temporary workforce), etc. If the TAKT time is lower, then we can add more shifts, or increase the overtime to cater to an increased demand etc. It is usually a good idea to create multiple plans. Plan A is used for normal demand, plan B is used for period of low demand and plan C is used for period of high demand.
If the TAKT time is varying all the time then it would drive non-value added activities in our process if we are constantly reacting to changes in the TAKT time. One approach that Lean uses to handle this in a production related process is to use a Heijunka box to balance the incoming workload so that TAKT time is relatively constant. For example, if the demand is varying, then an average demand is calculate for a specific period of time (say 3 months) and this is used to drive the TAKT Time calculations. Every three months, the TAKT time could be adjusted based on the inventory level and the expected demand variation during the next period. Of course, this approach results in extra inventory depending on the service level we desire from our process. For a service related process, inventory cannot be stored and usually demand cannot be held a constant. If the process is not capable of meeting the demand, the only option is to vary either the capacity by hiring other resources or using part-time labor to handle the additional demand during the peak times. The demand could potentially be adjusted by providing incentives or running other programs to motivate the customer to buy during the low periods or dissuade the customer from buying during the peak periods (say by raising costs etc.).
TAKT Time for Variable Processes
If the cycle time is highly variable while the demand is relatively constant, it is pretty straightforward to calculate the TAKT time but then using an average cycle time to compare with the TAKT time may not be very valuable. Let’ say that the cycle time varies from 20 hours to 100 hours depending on the complexity of the process. If the TAKT time is 40 hours, it is hard to say if this process is capable of meeting the customer demand. If we get a lot of jobs that have high complexity, then during that period, the customer demand may not be satisfied. Hence, the concept of TAKT time may not be very beneficial.
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