Just‑in‑Time (JIT)

JIT comes from the Toyota Production System and is one of the pillars of lean manufacturing, together with kanban, which signals what to replenish, and level production (heijunka). In the supply chain it means frequent deliveries of small quantities, often from suppliers located near the plant, timed to the production schedule. A stricter variant, just‑in‑sequence (JIS), delivers parts in the exact order in which they are fitted on the line.

Just‑in‑Time in practice

Delivery frequency cuts only part of the stock. A plant uses 400 units of a component a day, five days a week. With one weekly delivery of 2,000 units, average cycle stock is 1,000 units; with daily deliveries of 400 units it falls to 200. But if the supplier can arrive up to a day late, the plant needs one day of consumption, 400 units, as safety stock in both cases. Average inventory drops from 1,400 to 600 units, and two thirds of what remains protects against an unreliable supplier, not against batch size. Moving to two deliveries a day saves another 100 units and doubles the number of receipts again. Cutting the possible delay to half a day saves 200 units without a single extra truck. After the first step, JIT becomes a project about lead time reliability, not delivery frequency.

The second limit is where the stock ends up. Frequent small deliveries move it to the warehouse of the supplier or a logistics provider near the plant, and the supplier prices it in. JIT also assumes level demand: where volumes swing with seasons or product launches, the line‑side buffer has to be sized for the peak. And a supplier with no buffer of its own turns a single disruption in transport or at its plant into a stopped line.

Logio designs material flow from the receiving docks to the line and tests delivery frequency and buffer sizes with dynamic simulation before they change on the shop floor, as part of intralogistics and material flow projects. For purchased items, Veritico STOCK calculates supplier lead times from historical deliveries, including their deviation, and uses them as an input to safety stock.

Related terms

• Lean Manufacturing
• Safety Stock
• Lead Time
• Cycle Stock
• Kanban