6 ideas
Each process should receive only the exact parts it needs, in the exact quantity needed, at the exact moment they are needed — never producing ahead of demand. This eliminates the inventory buffers that otherwise hide inefficiency and tie up capital in unsold work.
Instead of an upstream schedule pushing parts forward, the downstream process withdraws what it needs and sends a card back as the signal to replenish exactly that amount. Information flows backward from final assembly while material flows forward, so production is governed by actual consumption rather than forecast.
A machine should be given the human judgment to detect an abnormality and halt itself immediately, rather than continuing to mass-produce defective parts. This frees one worker to oversee many machines and prevents a single error from propagating through the whole line.
Among all forms of waste, producing more than is immediately needed is the most damaging because it generates and conceals every other waste — excess inventory, unnecessary transport, storage, and the labor to manage it. Reducing inventory deliberately exposes the underlying problems a company would otherwise never be forced to solve.
When a problem appears, repeatedly asking 'why' about each answer drives past symptoms to the true root cause. A machine stopping might trace through an overload, a worn bearing, missing lubrication, a failed pump, and finally a missing filter — revealing the real fix only at the fifth question.
Large batch production looks efficient per unit but hides slow response, defects discovered too late, and the cost of carrying inventory. Shrinking lot sizes toward single-piece flow surfaces these hidden costs and forces faster setup, tighter quality, and genuine responsiveness to demand.