Just In Time (JIT)
Why a modern factory keeps almost nothing in its own warehouse
Imagine a restaurant kitchen that keeps almost no ingredients in its own fridge, instead having fresh vegetables, meat and dairy delivered in the precise quantity needed a few hours before each specific dish is cooked, never a day earlier, never a portion more. Just In Time manufacturing applies almost exactly this discipline to a factory's raw materials and components.
Rather than stockpiling large inventories of parts and materials as a buffer against uncertainty, a JIT-run factory coordinates tightly with its suppliers so that components arrive just before they are needed on the production line, often within hours, not weeks. This dramatically reduces the capital tied up sitting idle in a warehouse, and the physical space needed to store it, both of which cost money whether or not that inventory is ever actually used.
The approach originated with the Toyota Production System in Japan, developed specifically because Toyota, in the post-war period, could not afford the large capital buffers that stockpiled inventory requires, and turned that constraint into a genuine manufacturing philosophy that has since spread across global manufacturing far beyond automobiles.
The trade-off is real and became painfully visible during the COVID-era supply chain disruptions: a JIT system runs leaner and cheaper under normal conditions, but has far less buffer to absorb a sudden supplier disruption, a single missing component can halt an entire production line within days rather than the weeks a heavily stocked factory might have been able to ride out.
Whenever a factory shutdown is traced back to a shortage of one specific, seemingly minor component, a semiconductor chip or a small electronic part, a JIT inventory model, minimising buffer stock in normal times, is very often why that single missing part could stop an entire assembly line rather than being quietly absorbed from a warehouse reserve.