What is just-in-time (JIT) manufacturing?

Just-in-time (JIT) manufacturing is a term used synonymously with the Toyota Production System (TPS), the methodology that Lean manufacturing is largely based upon. The exact details of JIT’s origins are a bit unclear but can be traced back to post-World War II Japan. The term JIT is so interchangeable with TPS because it was during the 1970s that the Toyota Motor Company adopted the management system and played a key role in development.

In manufacturing companies must decide how to run their production system. The traditional choice was a push system in which production relies on a demand forecast, a prediction of what the rate of demand is. Production is then scheduled, and materials are ordered to meet the demand forecast. The push system can be beneficial in certain circumstances, but for the most part is an inefficient system. Predictions are hardly accurate and can quickly lead to overproduction, over-processing, waiting, and other wastes.

The JIT method is a type of system that is the opposite, a pull system. Instead of forecasting demand, the production schedule is based on actual demand and only begins when a customer order is submitted. The goal is to keep inventory levels to a minimum while producing a quality product on time. Not only can you save costs on raw materials and avoid overproduction, JIT production lines saves costs on raw materials, eliminates the risk of overproduction, makes it easier to identify defects early on, and is more flexible to work with.

An identified disadvantage to a JIT system is the possibility of disruption in the supply chain. Many of the other strategies in the Lean toolbox, however, are focused on flow of production. Creating value stream maps, setting up a cellular layout, and going on a Gemba walk are just a few tools you can utilize to avoid disruptions and unplanned stoppages.