Fundamentals

Just-in-Time (JIT)

Definition

Just-in-Time is a production and replenishment approach in which materials arrive only as they are needed, minimizing inventory throughout the system. It originated in the Toyota Production System.

In Practice

JIT replaces large buffers with frequent, small deliveries synchronized to actual consumption, often signaled by kanban cards or electronic pull signals. It only works when its preconditions hold: reliable suppliers, short and stable lead times, level production schedules, and high quality, because there is no stock to hide problems behind.

The payoff is substantial: less cash tied up in inventory, less warehouse space, faster exposure of defects, and quicker feedback loops. The cost is fragility. A single missed delivery can stop a production line within hours, which is why JIT operations invest heavily in supplier development and logistics reliability.

Automotive is the canonical example: seat assemblies arrive at the plant in the exact sequence of the cars on the line, hours before installation. The 2021 semiconductor shortage showed the flip side, prompting many firms to blend JIT with strategic buffers for high-risk parts, sometimes called just-in-case.

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