Heijunka is one on the lean tools and can in short be defined as Load and production levelling. Heijunka provides predictability by levelling demand, flexibility by decreasing changeover time, and stability by averaging production volume and type over the long term.
Example of Heijunka
Below is a simple example of smoothening production with Heijunka, for the example we have following demand for the month.
- Product A: 2000
- Product B: 1200
- Product C: 500
The daily demand for each product can now be calculated based on a 20 working days in the month.
- Product A: 2000/20 = 100
- Product B: 1200/20 = 60
- Product C: 400/20 = 20
This equals a daily production of 185 units.
Now the build ratio and production frequency for each type of product can be calculated.
- Product A: 100/20 = 5
- Product B: 60/20 = 3
- Product C: 20/20 = 1
The build schedule can now be setup.
- 1 unit of Product C to be produced, 3 units of product B and 5 units of product A
This is a very simple example of Heijunka for understanding the principle behind it, but the real situation is usually far more complex.
Heijunka vs. Traditional Production
If comparing a traditional production with Heijunka, then the traditional production aim at producing large lot sizes, whereas wit Heijunka it is about producing based on latest market demand.
If using our example above, then with traditional production we would produce the parts like this throughout the month. First we produce 500 pcs of product C, then production run 1200 pcs of Product B, and at the last half of the month the 2000 pcs of Product A is produced.
This unlevelled production creates following problems.
- Costumers don’t buy products in a pattern like this. E.g. If the want to buy product A in the beginning of the month it will not be possible.
- There is a risk of unsold items taking up inventory space.
- There is no balance in the use of resources.
If using the above example with Heijunka production, the production will run the products on shift and in smaller batches throughout the month. By reducing changeover time and using other lean methodologies, it is possible for a company to produce the products in any order or mix they want.
This gives following advantages.
- Reduced risk for unsold products.
- The use of resources (Labour and machines) is more balanced.
- The company is flexible to quickly react on costumers demand.
One way to go to get a levelled production is to implement takt time, which is a calculation of the amount of parts that must be processed at each workstation for a given timeframe to meet demand. It basically set the pace of production to the rate of costumer demand.
If you are interested in getting started with lean and implementing some of the methodologies in your company or business, then our 5S Training might be of interest to you. It is usually the first step to take when starting with lean, as it creates the foundation for further improvements to be implemented.
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