Roofing Time
In materials management, the replenishment lead time refers to the period for which a reorder is intended to cover material requirements. This period is usually measured in calendar days. In modern planning systems, the replenishment lead time represents a lot size method. If, for example, a replenishment lead time of 20 days is selected, enough material is ordered to last for 20 days from the time it becomes available in the warehouse, without falling below the safety stock level.
The ‘replenishment time’ lot size method requires a demand plan for the future and thus usually plan-driven scheduling.
Unlike lot size methods based on historical values, such as weekly or monthly lot sizes, replenishment time is based on future demand from already known customer orders and reservations as well as planned primary and secondary requirements. It thus represents a flexible lot size that responds to fluctuating demand and seasonality. Together with plan-driven scheduling, this is referred to as ‘dynamic range-oriented scheduling’.
Unfortunately, the range of coverage function is not available in many ERP and planning systems.
Our tip:
The replenishment time is an elegant tool for achieving the desired average stock range for an item, taking into account the safety stock. To do this, the safety stock is converted into a safety stock range (RWSB) based on the average daily consumption. The target range (ZRW) is then calculated as follows:
EDZ=2*(ZRW-RWSB).
For example: With a target range of 28 days and a safety stock range of 7 days, the replenishment time is 2*(28-7) = 42 days.
In planning systems that offer the replenishment time function, it is also a pragmatic tool for securing the remaining shelf life of items. To do this, the target range for the item must be set so that it corresponds to a maximum of the difference between the item shelf life and the remaining shelf life upon delivery. For example, if the item shelf life is 6 months and the required remaining shelf life upon delivery of the item is 4 months, the target range for the item may only be 2 months or 60 days.
