Supermarket in lean six sigma refers to a predetermined market inventory/storage. It's the location where a predetermined standard inventory is kept to supply downstream process. When any internal or external customer need any item they can retrieve the requisites from the supermarket . The supermarket basis the usage and demand, restocks the supplies .Supermarkets are located near the supplying process in order to have a quick check on customer's buying pattern, usage & requirements .
Before we go into further details of Supermarkets, lets understand what is a Three Pull strategy that is often put in use and how supermarket is one of the derivatives from the Three Pull strategies
A Pull Process is one where a unit/ workstation starts to work on its next order only when there is an available free slot on the output section . Which means if the demand of any item is high be it from an internal or external customer it would trigger the production of that item . Here the customer pulls order rather than the Push production where items are prepared no matter whats the demand is . The output section is not considered in Push production .
In Pull Process the inventories between workstations are managed & it directly influences and maximises the Lead time. The 3 forms of Pull connections are
1. Continuous flow : Products are worked on one by one with maximum inventory of one between workstations
2. Sequential Pull :A fixed quantity is determined & the sequence of product is defined, however a buffer with a defined maximum is allowed between workstations for variance.
3. Replenishment pull: Maximum number of products waiting where which type of product to be used is unknown
Supermarket is also known as a replenishment pull system where it manages inventory where variation of parts can be kept without knowing in what order the parts can be taken from the inventory/storage. A customer can take out parts randomly from the supermarket and the supplier replenishes the taken parts after a certain interval.
Supermarket can be implemented as connection between process steps when designing a Future state VSM
Following are the characteristics of a good Supermarket
Supermarkets must have access to wide range of products, which is why they need to be arranged in shelves. A FIFO approach can be followed here where everyone involved can immediately see the state of things.FIFO lanes be implemented when a particular workstation uses different colours and is not aware how many colours they need in a particular day.A Supermarket should contain a FIFO is each lane to help guide which colour used in what quantity for a particular day which in terms will help forecast & strategise production
Market location serves an important factor. It is important to help gauge on unit consumption & back it up with demand. Market Locator can be used as a sort of isolator between batch demand spikes & upstream supply .If a market is positioned at loading bay it will automatically receive indications of spikes of demand whenever a truck reaches for loading . So its known in advance when the trucks arrive there is a demand spike over a certain period of time. Thereby designating a location or a marked floor area to be the virtual truck area of moving items from virtual truck smoothly for a chosen period is required in supermarket
Products to be placed in plastic boxes , whose size would depend on the size of the material & each box is to be identified with a tag that shows the item details, the supermarket where it is located, supplier & quantity
Supermarkets should be located in loops.The sequential operations need to have a similar production pace (Cycle time, Downtime, Changeover time etc.),Have similar requirement of workers ( multi-skilling & multitasking) & hence to be located close to each other
The boxes become an indication of Cycle flow & Buffer stock depending on the demand. Each box leaving the supermarket triggers signal for the supplier in multiple forms like Same box needs to be placed . A Kanban card can be put in use to identify when the material goes out and becomes a replenished order and instead of taking out label the whole box can be put in use
Thereby supermarket is important as it manages material flow and eliminates waste , it also carries extra items in quantity from a range of a minimum and maximum without interrupting the flow and that results in increase in lead time & associated levels of WIP