Heijunka: A Production Leveling Strategy as Amazing as it Sounds

Heijunka: A Production Leveling Strategy
'Heijunka' is one of the production leveling strategies which was developed with an intention to curb the losses created by fluctuations in demand by consumers. Instead of mass production, it follows a production mix based on the average demand of products. This post talks about this strategy―the heijunka board/box―and its implementation.
Did You Know?
The Heijunka model is one of the vital elements of the Toyota Production Plan.
Manufacturing is a process that requires meticulous planning and production strategies. Every company strives to satisfy the demand of consumers to maintain its goodwill in the market. If the supply falls short of demand, consumers will automatically turn towards other options. Hence, manufacturing firms try to design a strategy that makes optimum utilization of their resources to satisfy consumer demand as and when it arises. Traditionally, the batching process has been used to plan production. However, it suffers from many limitations, and one of the most important drawback is that customer requirement may change at any level. It is constantly fluctuating, and in this case, there might be wastage of resources. That is because, in production, various resources are involved, such as labor, machinery, factory space, electricity, warehouse space, etc.
To meet such situations, the 'heijunka' system was developed. This strategy is popularly used by the Toyota Production System. It is a production leveling strategy that helps meet fluctuating demand, as well as reduce the wastage of resources. It concentrates on making an appropriate production mix. According to the heijunka model, to mitigate the loss of fluctuating demand, the average of the demand is usually taken, and production is spread over accordingly.
Important Terms

Mura: Instability and unevenness
Muri: Overburden on human resources or machinery
Muda: Wastage of resources

Mura and Muri create Muda, and production leveling strategies such as heijunka primarily aim at reducing muda. In short, 'heijunka' is a production leveling strategy that aims at reducing wastage of resources and meet sudden changes or shifts in demand.
Let's say a firm has demand for two products: A and B. Data given is as follows:

Monthly Demand
A: 1,500
B: 250

Let's assume that every month has 25 working days for the factory.

Computation of the production mix as per the 'heijunka' system.

Daily Demand
A: 1500 ÷ 25 = 60
B: 250 ÷ 25 = 10

Calculating the Build Mix
A: 60 ÷ 10 = 6
B: 10 ÷ 10 = 1

Thus, for every 6 products of A, 1 product of B has to be produced. Therefore, the production pattern will be BAAAAAABAAAAAA.
The following is an example of a heijunka box.
Heijunka Box
Scheduling System as per 'Heijunka'
The box displays the production intervals for different products. Its purpose is to produce in mixed proportions in small quantities, instead of mass producing, so that even if there is any fluctuation, production is not impacted much. It was developed by Toyota. The box usually has pigeonholes, where kanban cards are kept. These serve as scheduling system of heijunka. Each kanban card represents that particular unit of that product.

► The rows represent the products, and columns represent the time intervals for the next production.

► The kanban cards represent the products. This represents the time interval with which the production is implemented.

► In this case, A is produced every 30 minutes. B has higher demand, hence, it is produced every 15 minutes. Thus, you'll see two cards of B in this case. On the other hand, C and D will be produced every hour, at different time intervals.

► Of course, this does not guarantee that all customer demand will be met, since it is based on the average of historical data, and customer demand might fluctuate again. However, it will be better off than the batch system.
Advantages of Heijunka
► Reduction in wastage of resources, since the use of human power and equipment will be more stable.

► Due to more stability, human resources will benefit, since there will be lesser chances of overstress on one day, and sitting idle on another day. Instead of rushing, this system believes in being the tortoise in the game, stating that slow and steady wins the race.

► There will be more consumer satisfaction due to greater availability of the finished product as per the demand. Also, if there is no demand, there will be lesser levels of idle inventory. That will also reduce storage costs.
In the lean manufacturing model, this system is one of the pivotal methods used. It also helps in successful implementation of the 'Just-in-Time' (JIT) Inventory system. Toyota has proved that this system is very successful, and many companies are following suit.