Heijunka: Reduce Unevenness in the Production Process

What is Heijunka?

Heijunka is a lean manufacturing method that helps reduce overproduction by processing orders based on customer demand and avoiding bulk production in batches. It is a Japanese term for “leveling”, which allows organizations to optimize their inventory management system to meet customer needs and depend on customer buying rates. Heijunka is one of the thirteen pillars of the Toyota Production System and was established to save production costs and reduce unevenness in a production process.

What are the Advantages of Implementing Heijunka?

Heijunka in lean manufacturing aims to improve production workflow to better match the customer orders, reduce wastes, and minimize the chance of overburden. It helps the organization to achieve the following:

• efficiently meet customer demands;

• reduce inventory needs due to lesser batching process;

• decrease capital costs;

• increase profitability; and

• minimize manpower issues.

Two Ways of Leveling Production

Proper implementation of Heijunka provides predictability, flexibility, and stability in the organization. It helps level the demand, decrease changeover time, and average the production volume and type in the long term. There are two ways of leveling production using the Heijunka concept, it can be implemented by volume or type.

1. Leveling by Volume – deals with the number of items per type of product produced in each batch. It helps to see what products should be prioritized according to customer demand.

2. Leveling by Type – adds different sequences of what product is being produced in every batch. It maintains the needed variety of products to be produced on a weekly or monthly basis.

Heijunka Example

Scenario: A garment manufacturing company is producing different types of women’s clothes that include blouses, dresses, and coats and there is a demand for 100 products in a month. The operation is Monday to Friday for 6 hours per day. Each product requires 1 hour to finish in production.

In normal manufacturing production, they intended to produce products in batches and prioritize the production of the product with the higher demand. What they will do is produce blouses until they meet the monthly demand, then proceed to the next item in the line. The production pipeline would look like this:

In this kind of production process, they saw an issue in terms of customer demand. What would they do if the customer ordered 1 blouse, 1 dress, and 1 coat?. In this type of production pipeline, the customer can get her order by day 15 as the production of the coat will start on day 15. Also, what if the demand for coats increases due to weather changes? By implementing the Heijunka concept which aims to level the production, instead of producing products by batches based on monthly demand, they divide it into weekly production and create a variety of products in a week to sustain the demand of the customers on a weekly basis.

The production would look like this:

By doing this the team can produce the customer order of 1 blouse, 1 dress, and 1 coat on day 4, whereas in the previous case it can be delivered on day 15. On the other hand, if the demand changes in the next weeks, they can simply change the production pipeline and create a new set of lined up products to be produced based on trend and customer demand.

In implementing the Heijunka concept, the organization should also consider the factors that would affect the production timeline including the concept of Single-Minute Exchange of Dies (SMED). It would help in analyzing the situation if it would be difficult or it would take more time for operators to switch on producing one product into another than the usual time it takes.