JIT or Just-in-time technique is way of organizing and planning manufacturing operations, which is based on the belief that building buffers of inventory and manufacturing capacity is wasteful and must be eliminated wherever possible. This approach was first developed and implemented in Japanese manufacturing industries, particularly in Toyota.
In the traditional approach to manufacturing management, buffers of inventories and manufacturing capacities were built into the system so that even if there is a break down or shortage in one part of the manufacturing system the rest of the operations can continue. The logic forwarded to support this approach is that by a small additional investment at one point the chain of manufacturing operations the stoppage of the complete manufacturing line can be avoided. The flaw in this logic is that this additional investment at just one point is not enough. The buffer mus be built in at every point. This becomes quite expensive. So a better approach would be to have just enough, well balanced manufacturing capacity and inventories across the system, and ensure high utilization of this whole system by quickly reacting to and rectifying any problem encountered. This is the JIT approach.
To implement JIT successfully it is better to reorganize the manufacturing process in modular cells. Also high attention to quality is required so that there are minimum hold ups due to defective components or raw material encountered on shop floor.
The heart of JIT system covers, in addition to the core manufacturing activities, also the procurement function feeding the manufacturing, and distribution function after manufacturing. Core of JIT system is a system where action of procurement or manufacturing is taken only in response to requisition by the subsequent link in the complete procurement, manufacturing and supply process for material required by them - and they requisition these material so that they will receive material just in time for them to start processing further. In initial implementation of JIT this was achieved through kan-ban system consisting of physical containers and cards. However now, more sophisticated computerized systems have replaced such system in most of the cases.