just-in-time
Taking place at the time when it is needed, and not in advance.
just-in-time: inventory arrives when production needs it
Just-in-time, or JIT, is a production control discipline in which materials, components, and subassemblies arrive at the assembly line or work station at the exact moment they are needed, not before. The practice eliminates the intermediate storage and handling that traditional batch manufacturing requires. Instead of maintaining weeks or months of buffer stock in warehouses, a JIT operation receives frequent, smaller deliveries timed to match the production schedule.
The core mechanics depend on two elements: predictable, stable demand and reliable supplier performance. A manufacturer using JIT must forecast production accurately and communicate that forecast to suppliers with enough lead time for them to ship. Suppliers, in turn, must meet tight delivery windows without fail. Most JIT operations use a pull system, where the production line signals when material is needed, rather than a push system where material is sent speculatively. Kanban cards or electronic signals often trigger these pulls.
JIT operates at different scales. Some manufacturers apply it only to high-value items or bulky materials where storage costs are significant. Others, particularly in automotive and electronics, commit to company-wide JIT systems that govern everything from raw materials to finished goods. The automotive industry pioneered JIT in the 1970s; Toyota's system became the benchmark. JIT works best for products with stable demand and moderate complexity. Industries with long lead times, seasonal demand, or volatile sourcing face greater difficulty implementing it.
The main risks are supply chain disruption and quality failure. If a single supplier misses a delivery window by hours, the production line may stop. A defective batch arriving just-in-time becomes a defect arriving just-in-time, with no inspection buffer to catch it before assembly. Quality control and supplier management are therefore inseparable from JIT discipline. Many operations implement some safety stock of critical, long-lead items as insurance against catastrophic failure.
The financial and operational benefits are real: lower warehouse costs, reduced obsolescence, faster product turns, and less working capital tied up in inventory. The trade-off is operational fragility and dependence on supplier reliability. JIT is not a universal solution; it is a deliberate choice to reduce waste at the expense of redundancy, suited to stable, high-volume manufacturing environments with mature supply chains.