Many companies today are working towards the ultimate Lean goal of continuous or one-piece flow. They want to be able to make just what the customer wants when they want it.  Instead, what we often see is a “hurry up, then slow down” build-to-order approach. Customers’ orders vary from month to month, creating uneven production scheduling.  Build-to-order companies will be building huge quantities, paying overtime, and stressing their people and equipment one week, but then sending them home the next due to light orders. This environment can also create large amounts of inventory, hidden problems, and poorer quality. What many organizations fail to do is the difficult process of creating a true balanced lean workflow.  This is the Toyota concept of heijunka, leveling out the work schedule.

Heijunka is the leveling of production by both volume and product mix. This system does not build products according to the actual flow of customer orders. Heijunka takes the total volume of orders in a period and levels them out so the same amount and mix are being made each day. In a true build-to-order system you build products A and B in the production sequence of customer orders (e.g., A, A, B, A, B, B, B, A …). This causes you to build product irregularly.