Question

Discuss what is the 4-8-4-8 capacity buffer approach is in JIT, and how it can be useful in achieving the JIT goals.

Answer 1

Answer:

“Ideal” JIT is very rigid and this rigidity is certainly a problem, and this rigidity can only be maintained in an ideal world with ideal environment (where demand is constant and exactly predictable). However, in real world such ideal environment doesn’t exist and hence, the real-world JIT out of necessity contains measure to deal with unanticipated disruptions. Capacity buffer is a commonly used approach to tackle the unanticipated problems by the Japanese. By scheduling the facility to less than 24 hours per day, the line can catch up if falls behind. If production is going ahead of desired rate then the workers are either sent home or directed to other tasks. If production falls behind rate, either because of problems in line or because of changes in requirements, then the extra time is used for preventive maintenance. And two-shifting (4-8-4-8) technique is such a technique used, in which two eight-hour shifts are separated by 4 hours down periods, these down periods are used for preventive maintenance of the factory.

It helps in achieving JIT goals because if an unexpected occurrence, such as a machine outage, causes production to fall behind a workstation, then these WIP buffers (of 4 hours period between 8 hours shift) can prevent other workstation from starving. Thus, to keep the production rate constant, overtime will be needed. In effect, the Japanese have reduced WIP, so that the production occurs just-in-time, but they have maintained excess capacity, just in case.