Fluctuations in demand are a cost factor that is sometimes unpredictable in companies, despite extensive empirical data. Within the framework of lean management, Heijunka has been developed as a useful method for smoothing the production flow and thus counteracting waste.
The Heijunka principle is an essential building block of the Toyota Production System, with the help of which the output quantity within production is to be smoothed to such an extent that fluctuations in demand remain ineffective for the process. Production experts also refer to this as levelling. This also prevents the bullwhip effect, in which even small fluctuations in demand in one process, cause ever-greater fluctuations in demand in processes upstream. In the worst case, this effect leads to material bottlenecks.
Advantages of Heijunka
- Ensuring a continuous supply to the market
- Ensuring a steady consumption of supplier parts
- Avoidance of peak loads on employees and machines
- Creation of transparency about incoming and outgoing goods
8 steps to production levelling
For the smoothing of production flow to be successful, good planning is required.
1. Identification of the pacing process
This is the main area in the value stream and therefore the basis for the associated steps.
2. Identification of the cycle time
This value indicates how long a work step takes at best to meet the customer's demand in a timely manner.
3. Checking the EPEI details (every part every interval)
This key figure can be used to describe the time interval that elapses before the same product can be produced again.
4. Definition of the level of levelling and the setup families
Efforts can be reduced by sensibly grouping similar products. This can shorten setup times and can improve the performance of the production system.
5. Division of capacities
Here the harmonization of production sections is aimed at, leading to the approximation of a more demand-oriented production.
6. Creation of the setup-optimal, smoothed target sequence
This value will be used as a reference in the future.
7. Planning of the Kanban number
Based on the optimal target value, the future target can be defined and target stock levels can be set.
8. Measurement of the sequence quality
Based on the values, the improvement process can now be driven forward and measures can be developed.