The Best Known Lean Term – What Is Just in Time?

What is Just-In-Time?

The Just-In-Time methodology is used extensively in the automotive industry.

Just-In-Time (JIT) is one of the best known Lean terms but how does it apply to you and your business?

The Automotive industry in famous for it’s Just-In-Time approach to delivery by it’s suppliers. The basic principle is to have the right amount of products, where we need it, when we need it and to the acceptable quality level. Sounds like a simple enough concept.

The auto industry has refined and refined their processes along with their suppliers to make the JIT process work. Then they have decreased the deliver intervals into a measure of hours, not days or weeks. While this is all very well for a car company with high volumes and obedience suppliers, but how does this apply to you?

How to Setup Just-In-Time

First we need to understand the main value stream – the backbone of your manufacturing process or the one that would be run down a moving line, with everything else feeding into it, rather like a fishbone diagram. Then we need to understand the feeder lines and the parts that are needed to be fed into the main manufacturing process.

Once we have a list of parts and we know where they are needed in the build process, we need to determine the right amount and when they are needed.

To do this we need to gather information for each part number or line item:

  • Amount Used Per Assembly
  • How quickly We Use Them
  • How quickly Can Our Supplier Re-supply Them
  • How Reliable Is Our Supplier

This data should look familiar; it’s the same information we need when figuring out a kanban system. With this information we can begin to build the picture of how we need our parts to be delivered into our main manufacturing process. So with the basic principle of having the right amount of products, where we need it and when we need it, and some basic information about our manufacturing processes and parts supply, we can start to get an idea of what a Just-In-Time system would look like in your business. Next we will look at the considerations for implementing a Just-In-Time system.

Considerations When Implementing Just-In-Time

Implementing a Just-In-Time system is a huge undertaking and the rewards for doing so will also be huge. Previously we outlined the basic Just-In-Time (JIT) principle of having the right amount of products, where we need it and when we need it, as well as the basic information we need to collect to give us the full understanding of our manufacturing processes and parts supply.

Before we throw ourselves into full implementation mode, it is worth considering a few factors which will help determine the success of your JIT system, where to begin and what to avoid. As with implementing any new Lean system, we are striving for stability first, then improvement.

Internal or External Supplier

It may sound obvious, but considering whether your part comes from an internal supplier or external will determine how easy it is to get the supplier on board. Internal suppliers are a good place to start; get that simple system up and running first, then consider how to engage your external suppliers and get them involved

Supplier Reliability

The reliability or level of defects from a supplier will alter the numbers in your data table. Make sure you add a margin for parts that have know quality issues; if one part number has 10% defects, add 10% to the order quantity, assuming you will be returning that 10%


A consideration of risk is needed for each group of parts or suppliers. For parts, if running our of one part means complete disaster, then consider holding a safety stock until the robustness of the JIT system is established. Similarly for suppliers, know where the trouble may lie and ensure you have a buffer for that group of parts.

Internal Storage

While implementing a Just-In-Time system, consider starting with a two-stages process, creating an internal storage area that supplies into the main assembly process. Monitor that for a few weeks and continue to problem solve and get that part of the supply process running well. Having that buffer will allow you to focus on one the section of the process.

Implement In Stages

As well as implementing your JIT system in stages for the manufacturing process, also consider looking at one part family or supplier and use that pilot to get a better understanding of the issues your particular business and products will face.

With these aspects considered as you head out to start implementing a Just-In-Time system, remember that it won’t be smooth sailing. The ability of you and your team to problem solve and build a robust system will ensure your success.

Robert Chittenden

Author: Robert Chittenden

Robert Chittenden is a Senior Lean Consultant at TXM Lean Solutions