In this lesson we’ll review some of the origins of Lean Methods, as they relate to Material Flow. Even today, many of the Material Flow systems that we see in action have much older roots.
ORIGINS OF THE PULL SYSTEM
Material delivery based on a “Pull” system is nothing new. One example was the neighborhood milkman, doing his daily rounds and delivering milk in these recyclable containers. How does he know how much, if any, milk a customer wants? He would, of course, look on the front porch for empty containers, and replace any empties with full containers. Presumably the empties would then be returned to the dairy to be cleaned and reused. If the customer uses two containers, he/she will place the empties in a designated collection spot, and on a predictable schedule will receive two full ones.
While the empties are waiting to be refilled, how can the household ensure that they are not completely out of milk? They have some addition containers in the icebox. Not rocket science, right?
The milkman idea was extended, starting around the 1930’s, to the food outlets. Instead of having a clerk retrieve all the desired items from behind a counter, the customer would simply peruse the aisles and select what they wanted to buy, all by themselves. The store would monitor the shelves, and restock them as needed, from a storeroom or from an outside vendor.
The signal to restock in the supermarket was not an empty milk container, it was an empty space on the shelf. In order for this system to work, each item needed to have its own designed space and specific stocking quantity.
Let’s roll forward to today.
The basic method has not changed from the relative simplicity of the Piggly Wiggly supermarket of the 1930’s to today, where supermarkets average 38,718 stocked items. Every item has a certain amount of shelf space allocated, as shown here. As the products are removed from the shelves, scanned, and purchased, the inventory levels are monitored, and items reordered and restocked. Space is only allocated for a certain number of cans of Tomato Soup, for example, so it is impossible to stock more than the maximum number. The minimum number on a shelf is, of course, zero, but during the day high consumption items are restocked as space becomes available. Lower consumption items will be restocked overnight, when fewer customers will be impacted.
THE FORD RIVER ROUGE PLANT VS AMERICAN SUPERMARKETS
In the 1950’s the Toyota Motor Company toured the Ford River Rouge plant. While the Ford complex was huge and impressive, it was not something that Toyota at that time could emulate.
In the American supermarkets, however, was a model for material management that would be directly applicable to their manufacturing environment. The benefits: very tight control over inventory quantities, the storage space allowed, and the service to the end-user (in a factory, the operator). This was the origin of the material pull system that students will be reviewing in this Material Flow Memory Jogger program.
Sounds like enough history, let’s put it all together.
PUTTING IT ALL TOGETHER
The essence of an optimal Material Flow system is to deliver parts when and where they are needed, accomplishing the “Seven Rights” along the way. An example of this is a flow rack presenting small parts to an Operator. When a front tote is emptied, the one in back is pulled forward for use. Access is easy and ergonomic, and the inventory status is highly visible. When more parts are needed, they are supplied from a nearby Supermarket, pulled from a warehouse, or delivered directly by the external supplier.