Pioneered by the Lean guru Taiichi Ohno, referred to load leveling as “heijunka” (HIGH JUNK AH), meaning a technique for reducing the mode of (waste). Load leveling is a method for reducing large fluctuations in customer demand.
Use: Lean guru Taiichi Ohno can be quoted, “The slower, but consistent tortoise causes less waste and is much more desirable than the speedy hare that races ahead and then stops occasionally to doze. The Toyota Production System can be realized only when all the workers become tortoises.” You could have leveling by volume, or leveling by product. Leveling by volume: A family of products goes through essentially the same process steps.
The demand rate among the different families varies over time. Some families have small volumes. Other families have large volumes. Other families fluctuate between small volumes and large volumes. A floor supervisor might be inclined to want to produce the entire volume ordered by customer all in one run. With leveling by volume, what you do differently is you produce at the calculated long-term average demand and carry the amount of inventory that meets the variability of demand, stability of production processes, and the frequency of shipments.
Leveling by product: In this approach, the focus is on reducing the time it takes to changeover a process from running one family of products to another family of products. When successful, smaller batches can be produced because you don’t have to worry about long setup times. This author once ordered a rocker–recliner from a store that advised that the product was placed on ‘back order’ for three months. The factory most likely made large batches in the type and color that was being ordered. This author’s guess is that particular combination of type and color was not scheduled to be run for two to three months. If, however, they had leveling by product and could produce in smaller batches, the wait time may have been measured in days and not months. Ideally, the target is to produce in one piece flow.
