The practice of releasing production instructions to work areas and withdrawing completed product from work areas at a fixed, frequent pace. This practice can be used as a means of linking material flows with information flow.
In the illustration below, the material handler circulates through the entire route every 20 minutes. The handler begins by withdrawing production instructions (production kanban) from a heijunka box, then delivers the kanban to a production process where they are the signal to produce goods.
The handler picks up finished products from the production process and takes these to the supermarket. There the handler picks up production kanban from the collection box, takes these to the heijunka box for insertion in the box, and withdraws the next increment of production kanban from the appropriate column in the box as the cycle starts again.
Paced withdrawal serves to prevent overproduction and quickly alerts managers—in this case, in less than 20 minutes—if there is a production problem.