Lean manufacturing
Lean manufacturing is the production system, developed at Toyota, that maximizes value by systematically eliminating waste (muda) in seven classic forms: overproduction, waiting, transport, excess inventory, motion, defects, and overprocessing. Production is pulled by actual demand rather than pushed by forecast, problems are surfaced the moment they occur, and improvement is continuous rather than episodic.
Examples
Small batches via SMED: Cutting a press changeover from 4 hours to 35 minutes makes lot sizes of 500 economical where 5,000 had been the rule. WIP drops by about 80%, and a forming defect now surfaces within hours instead of three weeks later in a warehouse.
Pull to the supplier: An assembler converts a fastener line to two-bin kanban: 2,000 pieces per bin, replenishment triggered by the empty bin, deliveries twice a week. On-hand inventory falls from six weeks to nine days without a single stockout in the first year.
Definition
The system grew out of the Toyota Production System under Taiichi Ohno after World War II; Western researchers coined "lean" in 1990 after studying why Toyota's plants needed less of everything. Two pillars hold it up: just-in-time flow, making only what the next step needs when it needs it, and jidoka, stopping the line when a defect appears so problems cannot hide in volume.
Mechanically, pull runs on kanban signals, pace comes from takt time, and small batches with fast changeovers keep inventory from piling up between steps. Overproduction ranks as the worst waste because it manufactures the other six: it creates inventory, hides defects, and consumes capacity nobody asked for. An eighth waste, unused talent, is now commonly counted alongside the original seven.
Lean stops at the receiving dock unless suppliers run to the same rhythm, which is where lean procurement and vendor-managed replenishment come in. The common failure mode deserves naming too: adopting the artifacts (boards, cards, 5S audits) without leveled demand and exposed problems produces lean theater, not shorter lead times.
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