What is a Supermarket concept in Lean Manufacturing?

Understanding the Supermarket Concept in Lean Manufacturing: A Simplified Explanation

In Lean manufacturing, efficient flow is key to success, but there are times when maintaining a continuous flow or using a FIFO (First In, First Out) system is not feasible. This is where the supermarket concept comes into play as an essential part of the Pull system in Lean manufacturing. Supermarkets serve as a bridge between production stages, particularly when breaks in the flow are unavoidable.

Let’s dive into the basics of how supermarkets work in Lean manufacturing and why they are critical for maintaining efficiency when flow disruptions occur.

What is a Supermarket in Lean Manufacturing?

A supermarket in Lean manufacturing refers to a storage area used to manage and control the flow of materials or products between processes. The primary purpose of a supermarket is to act as a buffer between different stages in production when a continuous flow or FIFO system is not achievable.

Imagine a supermarket in the literal sense—just like how a grocery store stocks various items in designated areas for customers to pick what they need, a Lean supermarket holds products or materials for the next process in production to “pull” based on demand.

Why Use Supermarkets?

Supermarkets are used in situations where one-piece flow or FIFO isn’t possible. These systems ensure that a balanced flow of materials and products is maintained between stages of production, preventing overproduction or underproduction. In essence, supermarkets serve as a buffer, controlling inventory and ensuring that processes are not delayed due to supply shortages or excess inventory.

Here are a few reasons why supermarkets are essential:

1. Managing Variations: Supermarkets accommodate breaks, variations, or fluctuations in the process, ensuring that the next stage can continue smoothly.
2. Avoiding Stockouts: By maintaining a controlled level of stock in the supermarket, the production process avoids running out of materials or having too much inventory.
3. Adapting to Demand: Supermarkets allow for flexibility in managing varying customer demands by adjusting supply levels accordingly.

Types of Supermarkets in Lean Manufacturing

There are two primary types of supermarkets used in Lean manufacturing, each with different methods for managing inventory and flow:

1. Supermarkets with Kanban Signals (Maps)

A Kanban system is a visual management tool used to signal the need for materials or products to be replenished. In a supermarket using Kanban signals, visual cues like cards, lights, or flags are used to communicate when stock levels are low and need replenishing. These signals tell the upstream process to produce and deliver more goods based on actual demand.

For example, if a specific part or product in the supermarket runs low, the Kanban signal will alert the previous process to start producing more. This system ensures that only the necessary amount of stock is produced, reducing waste and overproduction.

2. Supermarkets with 2-Bin Systems (Physical Boxes)

In the 2-bin system, physical containers (or bins) are used to manage inventory. Each product has two bins, and when one bin is empty, it triggers a signal to replenish the stock. This system is particularly effective for managing small, frequently used items like screws, bolts, or fasteners.

Here’s how it works: When the first bin of a product is used up, it sends a signal (either through Kanban cards or another method) to refill the bin from the stock in the supermarket. While the first bin is being refilled, the second bin is in use, ensuring a continuous supply of materials without interruption.

How Supermarkets Control Flow

Supermarkets are used as part of the Pull system in Lean manufacturing, where production is driven by actual customer demand rather than forecasts or assumptions. This system allows companies to produce only what is needed, when it is needed, and in the amount that is needed.

When one-piece flow or FIFO isn’t possible due to variations in production, supermarkets step in to control the flow. The amount of stock held in the supermarket can be easily adjusted by adding or removing bins or Kanban signals, ensuring that inventory levels are always aligned with customer demand.

The Role of Supermarkets in the Lean Principle

In Lean manufacturing, the ultimate goal is to eliminate waste and optimize processes. Supermarkets contribute to this by maintaining just the right amount of inventory, preventing both overproduction (which leads to excess inventory) and underproduction (which leads to delays). By using a supermarket, companies can:

• Improve process efficiency: By ensuring that materials are always available, supermarkets help keep production moving.
• Reduce waste: Supermarkets prevent overstocking by only holding the necessary amount of inventory based on actual demand.
• Balance supply and demand: Supermarkets adjust to variations in production, allowing for flexibility in managing customer orders.

How to Implement a Supermarket in Lean Manufacturing

Here are the steps to set up a supermarket in your Lean production system:

1. Identify the Process Gaps: Determine where in your production flow a supermarket is needed. This could be between two stages that are not synchronized or where there is a significant variation in cycle times.
2. Define the Stock Levels: Determine the amount of inventory that needs to be held in the supermarket. This should be based on customer demand and the time it takes to replenish stock.
3. Set Up Kanban Signals or 2-Bin Systems: Choose the appropriate method for managing inventory in your supermarket. For smaller items, a 2-bin system may work best, while larger or more complex items may require Kanban signals.
4. Monitor and Adjust: Continuously monitor the stock levels and flow of materials in your supermarket. Adjust the inventory levels as needed to respond to changes in customer demand.

Conclusion

In Lean manufacturing, the supermarket concept plays a crucial role in maintaining an efficient and balanced production flow, particularly when one-piece flow or FIFO is not feasible. By acting as a buffer between processes, supermarkets ensure that materials and products are always available when needed, without creating excess inventory or delays.

Whether using Kanban signals or a 2-bin system, supermarkets are a flexible and adaptive solution that helps Lean organizations maintain smooth operations, reduce waste, and respond to customer demand with precision. As companies continue to optimize their processes, the supermarket remains a fundamental tool in achieving operational excellence.