How do lean manufacturing and just-in-time systems improve production efficiency?

"Manufacturers are discovering that they can better respond to rapidly changing customer demands, while keeping inventory and production costs down, by adopting lean-manufacturing techniques. Lean manufacturing streamlines production by eliminating steps in the production process that do not add benefits customers want. In other words, non-value-added production processes are cut so that the company can concentrate its production and operations resources on items essential to satisfying customers. Toyota was a pioneer in developing these techniques, but today manufacturers in many industries have adopted the lean-manufacturing philosophy. Another Japanese concept, just-in-time (JIT), goes hand in hand with lean manufacturing. JIT is based on the belief that materials should arrive exactly when they are needed for production, rather than being stored on-site. Relying closely on computerized systems such as MRP, MRPII, and ERP, manufacturers determine what parts will be needed and when and then order them from suppliers so they arrive “just in time.” Under the JIT system, inventory and products are “pulled” through the production process in response to customer demand. JIT requires close teamwork between vendors and purchasing and production personnel because any delays in deliveries of supplies could bring JIT production to a halt. Unexpected events like the September 11 terrorist attacks or the shutdown of ports due to Hurricane Harvey and the devastation and flooding caused by Hurricane Maria in Puerto Rico can cause chaos in the supply chains of manufacturers, resulting in problems for firms relying on JIT. But if employed properly, and in spite of these risks, a JIT system can greatly reduce inventory-holding costs and smooth production highs and lows."