The Difference between Pull Flow and Just-in-Time Explained

by Bernard Milian

There is sometimes confusion when we talk about pull flow.

When it comes to pull flow, there is often confusion with just-in-time supply chain management. In this article, we’ll define pull flow and just-in-time and explain the difference between the two. We’ll also discuss the importance of implementing buffers in a pull flow model to create agility and make operations more robust.

In the minds of many supply chain professionals, just-in-time comes with an increased risk of shortages because just in time dangerously close to just too late. These days, this is scary.

In the Demand Driven methodology, we try to implement a pull flow from the beginning to the end of the supply chain by integrating buffers.

Buffers? Of stock, of time, of capacity? But if we put in buffers then we can’t maximize the flows, right? Is this compatible with pull flow? Doesn’t lean promote the elimination of waste, and therefore of buffers?

It’s confusing, isn’t it?

What is pull flow?

My preferred definition of pull flow is replenishment action (purchasing, manufacturing, and inter-site transfers) which is triggered by actual consumption.

Actual consumption is a firm order, or better yet, a stock issue against a firm order.

For example, it is the information captured at the point of sale; the cash register of your supermarket or the validation of the shopping cart of your favorite e-commerce site.

If this information is captured and triggers a succession of actions in the upstream supply chain, then the flow is pulled from actual consumption.

Don’t look too far for examples of pulled flow, it’s likely you’re already using this technique to shop.

What is just-in-time?

A flow is said to be just in time when supply and consumption are perfectly synchronized.

At the extreme, the pack of yogurt that you're about to buy is put on the shelf a few minutes before you show up to put it in your cart.

Just-in-time flow, therefore, leads to a search for excellence by reducing waste, including waiting times and overstocking. Tightening up flows, in the sense of reducing delays, makes it possible to develop the agility of the supply chain. But tightening flows, in the sense of reducing buffers, risks weakening or even breaking the chain.

Every supply chain is confronted every day with disruptions, demand variations, and supply uncertainties, which make perfect synchronization illusory.

Buffers to pull the flow without defusing it

The notion of buffering that we describe in this article is a mechanism that creates agility as well as making operations more robust.

It is a question of positioning stocks, capacities, and spare time in the chain, sizing them as best as possible, and of controlling them continuously.

It is these last two points – dimensioning neither too much nor too little – and steering with clear management and action rules – that avoids tipping over to the fragile side of an over-stretched flow, or to the wasteful side of excessively high buffers.

A holistic model that needs to be continuously adapted

For the pull flow model to enable you to meet the needs of your markets without running the risk of supply disruption, you must design it as a company management model; it must cover all of your operations (distribution, production, procurement), it must be integrated into your information systems, and its adaptation must be supervised by your management team because it is really a matter of managing risk-taking to make strategic directions operational.

Conclusion

In conclusion, pull flow and just-in-time are two different techniques in supply chain management. Pull flow is the process of triggering replenishment based on actual consumption, while just-in-time is the synchronization of supply and consumption. Implementing buffers is important in a pull flow model to create agility and to make operations more robust.

It’s important to size the buffers correctly and to have clear management and action rules to prevent supply chains from becoming either fragile or wasteful. By designing a pull flow model as a company management model, it can cover all operations and be integrated into information systems, making it continuously adaptable to meet market needs.

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About the Author
Bernard Milian has more than 35 years of experience in developing agility within industrial and distribution supply chains. He has more than 25 years of experience in Supply Chain Management and Continuous Improvement / Lean 6 Sigma transformation. He has served as a Supply Chain Director within French subsidiaries of world class corporations, in the automotive, electronics, medical devices, furniture and metallurgy industries, B2B, B2C, manufacturing and distribution environments