Lean Tools: Heijunka¦Leveling the Workload

Lean manufacturing includes a set of principles that Lean thinkers use to achieve improvements in productivity, quality, and lead time by eliminating waste.

There are many tools and concepts that Lean companies employ to support the above principles and eliminate waste. Here is one of those tools to know.

Heijunka Production Leveling

Production leveling, also known as production smoothing, or by its Japanese original term heijunka. It is a technique for reducing the Mura (unevenness) which in turn reduces Muda (waste). It was vital to the development of production efficiency in Lean manufacturing.

The goal is to produce intermediate goods at a constant rate so that further processing may also be carried out at a constant and predictable rate. Where demand is constant, production leveling is easy, but where customer demand fluctuates, two approaches have been adopted: 1) demand leveling and 2) production leveling through flexible production. To prevent fluctuations in production, even in outside affiliates, it is important to minimize fluctuation in the final assembly line.

A heijunka box is a visual scheduling tool. It is a concept originally created by Toyota for achieving a smoother production flow. While heijunka is the smoothing of production, the heijunka box is the name of a specific tool used in achieving the aims of heijunka.

A heijunka box is a wall schedule which is divided into a grid of boxes or a set of pigeonholes or rectangular receptacles. Each column of boxes representing a specific period of time, lines are drawn down the schedule/grid to visually break the schedule into columns of individual shifts or days or weeks. Colored cards representing individual jobs (referred to as Kanban cards) are placed on the box to provide a visual representation of the upcoming production runs.

The box makes it easy to see what type of jobs are queued for production and for when they are scheduled. Workers on the process remove the Kanban cards for the current period from the box in order to know what to do. These cards will be passed to another section when they process the related job.