What is Heijunka?
Heijunka is a Lean technique for reducing unevenness and minimizing the risk of overburdening in production processes. Heijunka is a Japanese term that literally means leveling. You can use it to react to changes in demand and maximize your capacity.
Heijunka allows you to stop working in batches and begin processing orders based on customer demand. You can reduce inventory costs by reducing the amount of goods you have in reserve.
Your team and your process will also be protected when the demand increases, as you’ll be producing according to takt times, or, simply put, your average selling rate.
Toyota is the most prominent example of a business that uses Heijunka. Toyota, the Japanese automaker, has abandoned its traditional method of working with batches to schedule car assembly on a production line according to demand.
Heijunka lets you produce and deliver your product at a constant pace, so you can respond to changes in demand according to the average. The method can be used to level production in two different ways:
- The leveling of the volume
- The leveling of types
The Leveling of Volume
You need to eliminate batch processing to only produce what is ordered. This will keep your inventory costs down.
Lean, in its purest form, teaches you to only start new work when an order comes. This may not be the best option for companies that receive a constant stream of orders and must adapt their workflow in order to meet demand.
Heijunka lets you level your production based on the average number of orders that you receive.
If, for example, your demand fluctuates daily (Mon 3, Tue 10, Wed 5, etc.), it would be wise to implement Heijunka in order to level the production by volume. It would be wise to use Heijunka in order to balance production based on volume.
You can then establish a steady flow of work, and complete 5 orders per week to meet the demand.
You can keep your business running smoothly without any extra stress when orders increase during the week.
The Leveling of Type
Heijunka can be used to manage a portfolio of products. You can organize your work based on the average demands for each product.
You create enough goods to satisfy the average demand of the product portfolio.
If you receive 10 orders per product per week, but only 2 orders per Product B, then you will need to increase your production capacity so that you can produce 20 products each week.
In this case, however, you will need to use Heijunka in order to further level the production so that you can meet demand for every product.
Toyota, to meet this challenge developed an interactive tool called Heijunka Box to help visualize how many vehicles are needed for each model.
What is Heijunka Box?
A Heijunka Box is a tool that helps you visualize the tasks needed to meet customer demands.
It is a system that visualizes the orders for each product and then, based on average demand, levels a production order to achieve an optimal flow.
Heijunka boxes are usually arranged in a grid, with each row representing a different type of product. Each column represents the quantity that must be produced for each day during the week.
Each horizontal row represents a product in the portfolio. The vertical columns represent the days of the week. Each box is a container that holds the work items your team has to complete.
Heijunka boxes can be visualized differently. You can draw the box on a flat, smooth surface such as a wall or window. Then you can place work items in it using sticky notes. Or you can build a real box based on your preference.
You may have to put multiple orders or none at all in each box depending on your takt. Each item in the Heijunka boxes is a card that later moves through the manufacturing process.