It is difficult if not impossible to improve your aim at a moving target. The same principle applies to lean manufacturing. It is important to establish a baseline in order to take the next steps in improving the capability of the production system. Having established product-based work cells, synchronized flow and small lot production, you want to achieve not just demonstrated performance but proven performance. Demonstrated performance is the ability to do it once. Proven performance is the repeatability that comes from having an effective process in place and having the supporting infrastructure holding it up.

Having made the transformation to lean, how can we keep the systems operating at a high level of efficiency and continually improving? Without continuous improvement the lean system will not just stay the same - they will degrade. Achieving a stabilized operation or demonstrated performance is the first challenge - proven performance is the next.