2-Bin Systems
IMPLEMENTING LEAN
Warning
If you have not yet read the section on “Kanban Cards”, please go back and familiarise yourself with them. Understanding Kanban cards and re-stocking procedures will greatly help your understanding of 2-Bin Systems.
2-Bin Systems
One of the easiest ways to keep track of inventory, materials and supplies is to make use of a 2-Bin System for each item. It is a very visual way of managing stock. It only requires two containers for each item. In its most basic form, one is being used actively, and the second bin is backup and reserve stock.
The Active Bin
The Active Bin is the first container. This is the one that is being picked from and actively used by workers. This will be slowly depleted until empty. When it is empty it will serve as a visual signal that you should re-order or replenish the stock.
The Reserve Bin
The Reserve Bin is the second container. This is where you keep your reserve and backup stock. When the Active Bin has been emptied, you should switch to the Reserve Bin whilst the Active Bin is being refilled and restocked. In doing so, the Reserve Bin has now become the Active Bin, with the other bin sitting empty.
It is an easy way of reducing the 3rd waste, Excess Inventory. You ensure that the materials and items are always readily available, without the need for too much stock. You only restock it at a specific point. As it is highly visual, it helps reduce the risk of running out of essential items unexpectedly, which could lead to other wastes such as Waiting.
For Re-ordering on the Active Bin, you could easily use a Kanban card with re-ordering details, as previously discussed in this chapter.
Example
In the toy factory, they use a particular type of bolt to secure the wheels to the body in one of their toy cars. They buy these bolts in bulk of 1000 at a time. The minimum number is 1000. Rather than count the bolts to know when to re-order them, they have implemented a 2-Bin System.
They started by buying 2000 bolts to ensure each bin was full. At the bottom of each box is a Kanban card with the details of re-ordering.
When they have used the 1000th bolt from the active bin and it is empty, they pull the Kanban card, place the empty bin in the marked location, and start using the reserve bin. In this process, the reserve bin becomes the active bin, with the reserve bin sitting empty.
It takes around 5 days for the bolts to arrive, and in the meantime, they have used around 600 bolts. The reserve bin is re-filled with 1000 bolts and placed behind the active bin which contains ~400 bolts. Once they have used those remaining 400 bolts, the process repeats.
In the few months they have been running this system, they have never run out of that bolt.
