Definition of Heijunka:
A Japanese term that means “leveling.”
When implemented correctly, heijunka provides predictability by leveling demand, flexibility by decreasing changeover time and stability by averaging production volume and type over the long term.
The heijunka box helps visualize the optimized production schedule. Each square on the board represents a kanban to signal production of a single product. The “pigeon holes” are implied – the kanbans fit in them. Each square on a given day represents one product to be made. In this example, for the timeframe Monday through Friday, two of the pink products are made each day, represented by two squares (kanbans). Heijunka boxes are literal boxes on the production floor that signal workers to know what to make next during the day.