Heijunka Principles and Application Simplified

If you’re wondering whether heijunka is another Japanese term that’s designed to make our work lives better, you’re absolutely right.

Heijunka is a Lean technique similar to other Japanese principals like kanban and kaizen. It is also one of the 12 Pillars of the Toyota Production System. While it may not be as popular as other Japanese lean techniques such as kanban, kaizen, and Just-in-Time, it is an effective approach to establishing a smooth flow of work.

Let’s explore more about what heijunka is and how you can use it.

What is Heijunka?

Pronounced hi-june-kah, it is a Japanese term that means “leveling.” The Lean Lexicon 5th edition defines heijunka as:

“Leveling the type and quantity of production over a fixed period of time. This enables production to efficiently meet customer demands while avoiding batching and results in minimum inventories, capital costs, manpower, and production lead time through the whole value stream.”

The heijunka principle simply allows businesses to respond to changes in customer demand by establishing a standard or leveled flow of work.

Heijunka vs. Batching

Most companies, especially manufacturing ones, would resort to a batch production approach thinking that it is a cost-effective solution. Batching is popular because there are minimal costs due to changeovers and there is prepared stock to meet customer demand. But these so-called “benefits” can actually do your company more harm than good. When you batch your production, you essentially meet these problems:

• Inability to respond to changing customer demand – No matter how many forecasts we produce, it is very hard to predict and be certain of customer demand. There will always be fluctuations and variations. If we consistently produce in batches, we may lose the opportunity to provide the customer with the product that they want, simply because we are not producing it at that time.
• Capital being tied to inventory – Because companies want to make sure they have enough stock to provide to customers, they produce large quantities. But these effectively get stored as inventory and don’t make the company any money until it eventually gets sold. There can be instances where the company needs to sell the products just to free it up. This is certainly not ideal in terms of profitability.
• Overworked machines and personnel – Producing in large quantities every time can eventually lead to machine and staff breakdowns. This can also affect the quality of the final goods, which can lead to more wastes or muda in Japanese.

These are the main problems that heijunka aims to solve.

Heijunka allows companies to produce as close as possible to what demand dictates. This is done by producing smaller batches and creating different types of product at one time. Companies can be more flexible to demand changes, minimize inventory, and balance out the use of its resources with this approach.

How Heijunka Works

Heijunka aims to meet customer demand by leveling the volume and types of products produced in any given production cycle. To understand this better, let’s discuss the factors affecting the implementation of heijunka: Flexibility, Stability, and Predictability.

• Flexibility – Heijunka prescribes the production of various types of product in one timeframe. For example, in a 20-minute production period, the company needs to make 3 types of products using the same machine. Therefore, it will changeover twice within the 20-minute period. The time it takes for the machine to changeover to produce one product to another needs to be as fast as possible so that they can produce all 3 variants of the product within the time allotted.
• Stability – Setting the average amount of products in each type that needs to be produced in each lot allows the process to operate in a steady fashion. Companies would need to know their takt time or the time it takes for a product to get finished in order to meet customer demand in order to come up with their production schedule.
• Predictability – Companies need a way to forecast customer demand. It won’t always be accurate, but it’s still better to gauge how much of a product is really needed by the market and base the production schedule from there. This will make the production more predictable and manageable for the company.

Given these three factors, we can see that heijunka can actually be achieved with Just-in-Time already in place in the system. It also requires that the company has already analyzed and reviewed their value streams so that they can optimize it enough to actually make heijunka work.

The Heijunka Box

Companies would use a scheduling tool called a heijunka box when implementing this technique. The heijunka box indicates the schedule of the production, outlining the types of products that should be produced at a given time period through kanban cards. This allows workers to know how much of each product type should be made and when they should make it.

While heijunka is not exactly rocket science, applying it to real-life production situations can be more complex than we can imagine. It may take a while before you actually get a hang of things. It is important to stay attuned to customer demand and adjust your process as needed. It should also be the company’s priority to continuously improve and optimize their operations so that a more leveled workflow is established.

Applying heijunka can be a trial and error situation. Don’t expect to nail it the first time. But once the company has it in place, they can be sure to reap the benefits of a more standardized flow of work.