Just-in-time is system of production that makes and delivers just what is needed, just when it is needed, and just in the amount needed. JIT and jidoka are the two pillars of the Toyota Production System. JIT relies on heijunka as a foundation and is comprised of three operating elements: the pull system, takt time, and continuous flow.
JIT aims for the total elimination of all waste to achieve the best possible quality, lowest possible cost and use of resources, and the shortest possible production and delivery lead times. Although simple in principle, JIT demands discipline for effective implementation.
The idea for JIT is credited to Kiichiro Toyoda, the founder of Toyota Motor Corporation, during the 1930s. As manager of the machine shop at Toyota’s main plant, Taiichi Ohno said his first steps toward achieving JIT in practice came in 1949–50. (Ohno 1988, p. 31.)