What is heijunka?
Heijunka is a Japanese term for a level loading of demand and is a fundamental component of a pull system.
It s also known as production levelling or production smoothing and its aim is to produce items at a constant rate so that they flow through the production process with minimum lead time and no waiting.
In any process, there are fluctuations in performance (for a variety of valid reasons). Heijunka seeks to level the fluctuations and the system is constantly monitored as part of a continuous improvement policy.
If you have a constant demand, production levelling is an easy process. However, for most organisations, customer demand demand fluctuates so a twin approach is required
1) demand levelling at the sales order entry point and
2) production levelling against known throughput capacities based upon the product mix at any point in time
To prevent fluctuations in production and to optimise revenue it is important to minimize fluctuation in the final process and to ensure that every preceding product/service flows smoothly to and through the end process. This where the concept of one piece flow is put into action. However, to accommodate this philosophy any change over time in the flow lines must be small so that they do not inhibit flow. This is why SMED (single minute exchange of dies originated by Shigeo Shingo) is an integral part of heijunka.