Variability and uncertainty magnifies the significance of interdependencies within production systems (queuing effect). Thus, it is very important to reduce variability not only in terms of deviations to target values but also in terms of variance in relation to tolerance limits. Variability in the bottlenecks, in special, has a dramatic effect on the capacity of the all production system since the common approach when delays occur is to attempt to match the overall processing capacity with the bottlenecks capacity (Shingo 1988). In production systems that are implanting Just-in-Time, the reduction of variability in products and time is a fundamental requirement. In those systems, everything can come to a halt if one sub-product is not within tolerance limits and delivered at the right time