Heijunka

What is Heijunka?

Heijunka (hi-JUNE-kuh) is a Japanese word for leveling. It is part of the lean methodology of process improvement that helps organizations match unpredictable customer demand patterns and eliminate manufacturing waste by leveling the type and quantity of production output over a fixed period of time.

How Does Heijunka Work?

It may be easier to understand Heijunka and how it can improve the production process by contrasting it with the traditional production method of batching.

Batching has been a commonly used method for organizing the manufacturing process since the invention of mass production. Batching produces large lots of products without taking into account the fluctuation of customer demand. The output that is not immediately purchased by the customer is placed in inventory.

The traditional method of batching has several drawbacks:

• Customer demand is rarely predictable. When customers follow an unanticipated buying pattern, the manufacturer may experience confusion and disorder.
• The demand on upstream processes is erratic.
• The cost of unsold goods held in inventory decreases profitability.

Batching also results in uneven product quality and overworked equipment and personnel, which combine to create the villain that the Lean production process fears the most – waste.

What’s so Great About Heijunka?

Heijunka helps avoid the inefficiencies of manufacturing in large lots by putting the production process closer in line with customer demand. The flexibility that Heijunka instills brings three benefits to manufacturing:

• Predictability – Happens when demand is level
• Flexibility – Achieved by reducing changeover time
• Stability – Averaging production volume and type over the long term

Organizations that implement a Heijunka leveling schedule in their manufacturing processes can create a number of advantages over their competitors:

• Flexibility to produce what the customer wants when they want it.
• Reduced inventory of unsold goods.
• Balanced use of labor and machines.
• Predictable demand on the upstream processes and suppliers.

Heijunka requires adjusting production to mirror customer demand as closely as possible. When the company makes all product types and maintains a small inventory buffer throughout a year, there is greater flexibility to meet changing customer demand patterns. The buffer inventory will be liquidated during the year and production will be able to meet periods of peak demand and erratic customer purchasing.

Process Adjustments for Heijunka

Lean six sigma encourages manufacturing every type of product every day. This requires manufacturers to minimize the changeover time needed to convert the line from producing one product to another.  The effectiveness and financial viability of Heijunka are determined by the efficiency of the changeover process.

How to Implement Heijunka

The first step in leveling production to match customer demand is to set the pace of manufacturing according to what Heijunka calls Takt time. This is the customer buying rate, or the time it takes to finish a product to meet customer demand. Matching the production rate to customer demand helps create a level manufacturing process that is free of bottlenecks.

Manufacturers exist to meet customer demand as smoothly and predictably as possible. However, the customer buying behavior is frequently unpredictable. Using Heijunka to match customer buying patterns helps manufacturers fulfill the customer’s needs and reduce waste in the production process.