HEIJUNKA [平準化]

    

Summary

What is Heijunka?

Heijunka is in the Lean concept that aims to smoothing the production schedule. By doing smoothing on the scheduling of, it will obtain advantages in the process of lead time.

The relation between Predictability, Flexibility and Stability Is Heijunka – When implemented correctly, heijunka provides predictability by leveling demand, flexibility by decreasing changeover time and stability by averaging production volume and type in a long term.

Lean is a management system that is fully focused on efficiency. Lean is "a philosophy of long-term growth through efforts to increase value for customers, society and economy in order to reduce costs, accelerate time to provide interventions, and improve the quality through the elimination of waste in total" (Boss and Frank, 2013: 170; Lean Interprise Institute, 2009 ). Lean discoursed first time in the automotive industry by Toyota management system in the 1890s. since then, lean attracting various industries in the world and applied in many aspects besides manufacturing.

Taiichi Ohno was a Japanese industrial engineer and businessman.
He is considered to be the father of the Toyota Production System

This is an illustration of the principle of smoothing (leveling) where the workload be leveled for the sake of continuity (consistency turtle) regardless of variation orders (speed rabbit). Ohno went on to tell that the Toyota Production System (TPS) can only be realized if everyone becomes slow tortoise and steady rather than run fast and jerky like the rabbit, as in traditional production systems.



No mass production system can be continuously responsive to gyrating orders without suffering from muri (overburden of machines, managers, and production associates), and mura (unevenness in productivity and quality). And mura and muri together create muda (waste).

TPS around this by leveling the load and do not always produce based on the order. This concept is known as heijunka; which is based on the description above, can be interpreted as a system of production-leveling that produces the right product mix as demanded by the customer by making optimal utilization of the available capacity.

What Heijunka does?

• Stabilizes production volume and variety by consolidating total number of customer orders
• Spreads out the production in an even manner through-out the day
• Ensures high order fulfillment rate
• Ensures internal production is balanced
• Established capacity is not over or under-utilized

In English, heijunka has two different meanings, but interconnected. There are:

1. Leveling of production by volume (production leveling) 

Adjust the production schedule of activities with the aim to control inventory, reduce lead time, and producing diverse products with a volume corresponding to the request is desired by consumers.

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From Figure on the right it is known that the characteristics of JIT, including:

• meet customer demand right when there is demand (just-in-time);

• reducing inventories of finished goods (finished goods);

• work schedule can not be predicted; and

• suppliers are located in the upper (upstreams) must have high variability in order to meet customer demand variations.

And, production leveling characteristics, including:

• meet customer demand based on the total production leveling specified period (in the case above in the weekly);

• inventories of finished goods (finished goods) is made for short-term periods which have high demand;

• work schedule can be predicted; and

• production stability is transmitted throughout the supply chain (supply chain) to reduce inventory suppliers.

2. Leveling production by product type or mix, (leveling product)

before vs after

If there is a product that has more than one type of product then leveling is a critical way to avoid things that are not desirable. Producing goods ABC in one day.

Heijunka Box?

Now that you have a good idea of what the Heijunka concept is, you should learn about the Heijunka box. A heijunka box (it can also be a wheel or board) is a simple visualization of production using kanban cards to signal production according to a specified interval of work (e.g., per day). It is used by production staff and is highly regarded in visualizing processes.

Challenges of Heijunka

1. Requires major tool redesign to gain flexibility
2. Large inventory of finished goods
3. Requires a predictable environment as well as timely-accurate data to implement
4. Proper co-ordination with the customer to project better future demand
5. High degree of discipline within the workforce
6. Thought out work standards must be followed all the times
7. As there is little operator leeway it can result to resistance due to lack of flexibility

With heijunka, any amount of the order-will always be calculated (no matter how many the order will always exist in a shorter periodization). This maintains the continuity of the supply chain and provide a better service to all customers feel satisfied.

*Note :
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