Great question! Takt time represents what we’ll call the “drumbeat” of the process. It’s the rate at which the products or services must exit the process in order to meet the customer demand. This is a key concept when using a Value Stream Map to prioritize where to focus improvement efforts. If the process cannot meet customer demand, then the improvements can focus on reducing defect rates, increasing the availability of people, equipment or materials, reducing non-value adding steps, etc. The number of operators is a factor in what the process is able to produce, but it is not part of the Takt Time calculation.
The formula looks like this:
- Takt Time = Net Available Work Time / Customer Demand
One example is to determine the Takt Time for the lunch rush. The rush lasts from 11:30am to 1:30pm and the average number of orders in that period is 100. What is the rate at which orders must exit the process? What is the drum beat?
- Lunch Rush Takt Time = 120 Minutes / 100 Orders
The answer is 1.2 minutes or 72 seconds. This means that a lunch order must come out of the kitchen every 72 seconds in order to meet the customer demand. It does not mean that it should take 72 seconds for the kitchen staff to make a lunch order. That is a measure of work time. If the process is unable to meet the Takt Time, then customers are left waiting and dissatisfied. A Lean Six Sigma project might focus on issues such as the distance from the assembly area to the supplies, or the number of times supplies run out. It might focus on whether or not there is enough staff to meet demand (the number of operators you mentioned above), but we always say, “creativity before cash.” Let’s look at the process first!
I hope that was helpful!