Takt Time: The Heart Beat of One-Piece Flow
In competitive rowing, a key position is the coxswain—the little person in the back of the boat who is calling “row, row, row.” He or she is coordinating the activities of all the rowers so they are rowing at the same speed. Get a maverick rower who outperforms everyone else and guess what!—the boat gets out of kilter and slows down. Extra power and speed can actually slow the boat down.
A similar thing occurs in any manufacturing or service operation. Make one particular department extra efficient and it can actually bury other departments in excess inventory and paperwork and slow them down, making a mess of things. So there is a need to coordinate activities. When you set up one-piece flow in a cell, how do you know how fast the cell should be designed to go? What should the capacity of the equipment be? How many people do you need? The answer is the takt time.
Takt is a German word for rhythm or meter. Takt is the rate of customer demand—the rate at which the customer is buying product. If we are working seven hours and 20 minutes per day (440 minutes) for 20 days a month and the customer is buying 17,600 units per month, then you should be making 880 units per day or one unit every 30 seconds. In a true one-piece flow process, every step of the process should be producing a part every 30 seconds. If they are going faster, they will overproduce; if they are going slower, they will create bottleneck departments. Takt can be used to set the pace of production and alert workers whenever they are getting ahead or behind.
Continuous flow and takt time are most easily applied in repetitive manufacturing and service operations. But with creativity the concepts can be extended to any repeatable process in which the steps can be written out and waste identified and eliminated to create a better flow Using the Toyota Way to Transform Technical and Service Organizations. At the end of this chapter is a case example of creating job summaries in Navy ship repair facilities. There are many other examples my associates and I have worked on in service operations—completing bills of materials for engineering of ships, processing people through a security office of a Navy shipyard, processing new members into a professional association, reimbursing employees for expenses, processing job applicants …. And you can think of many more. Obviously, it’s easiest to apply the concepts of takt time and one-piece flow in relatively high-volume and repetitive service operations in which there is some consistency in the cycle time per unit, but the Toyota Way is never satisfied with doing only what is easy.