Lean Manufacturing in Simple Terms: Pulling Versus Pushing

In our American culture, we are very accustomed to going to a grocery store, or a hardware store, or any other kind of store, and finding all of the items we had set out to purchase. Not only do we expect to find our desired product in adequate quantities, we also expect to find it in a variety of colors, shapes, and sizes. Let's face it. We are quite spoiled when it comes to shopping. It seems like our manufacturers and our merchants have always gone out of their way to provide large inventories of goods.

Perhaps that thought process, however, makes it difficult to grasp the idea that in a lean manufacturing world, the excessive inventories that come from improved manufacturing methods and healthy supplies of raw materials should actually be considered a form of waste.

Lean manufacturing is best achieved when the product is pulled through the system rather than pushed through the system. Let's discuss each of the two methods.

Push System. A "push" system is one where the manufacturer builds as many items as possible each day, anticipating the need in the marketplace. The product is "pushed" down to the next level of manufacturing or sales, regardless of whether it is needed there or not. The risk, therefore, is the chance that the demand will not match the manufacturer's predictions, and an excessive inventory will have to be stored, managed, and possibly even liquidated at some point in the future. Or on the other hand, if the inventory is not sufficient for the demand, the manufacturer's risk includes the potential for reduced customer satisfaction because the market wasn't properly supplied. Either way, the push system requires good information to be reasonably effective.