Over the last few articles, we have been discussing the importance of Production flow and the different Lean tools that are available to control flow. Supermarkets can be useful when sections of Production work very differently and balancing can be difficult to achieved. After the analysis of part usage and production lead time is complete and supermarket stock levels have been determined, it is time to consider how to make your new supermarket visual and easy to audit. The two main approaches are to establish a kanban system or a two-bin system.
A two-bin system is the simplest visual control system for a supermarket.
As the name implies, a two-bin system has two bins or containers for each line item in the supermarket. This works best when the parts are small and not expensive.
The front bin is used to take parts from by the customer cell. When the bin is empty, the bin is moved to the collection location. The customer cell will then take parts from the second bin. The empty bin is taken to be refilled, then replaced behind the second bin, before that bin is emptied.
As with any supermarket system, you need to considered part usage, lead times and risk as part of your analysis to determine stock levels in each bin and the time to replace when compared to the usage. If parts have a short lead time, the bin refilling time may include ordering the parts, having them delivered and then returned to the line. If the part reorder time is long, then the stock levels will need to be higher or a secondary storage area may be needed.