Fixed Time Quantity

There are two types in the multiperiod inventory systems. One is the fixed order quantity model which is also called as the economic order quantity or the Q-model and the other one is fixed time period models which is referred to as the periodic review system, the fixed order interval system and the P-model. The main purpose of the multiple inventory system is to make sure that a particular item would be available all through the year in an on-going bases. This would be done by ordering that particular item for multiple times all through the year. There would be logic in the system which will dictate the actual quantity that is ordered and the timing of the order. Fixed time quantity is similar to fixed order quantity but it differs from it in certain ways.

The fixed order quantity is event triggered on the other hand the fixed time period models are time triggered. An order is initiated by the fixed quantity models when a specific reorder level is occurred. So, in the fixed order quantity the event of reaching the specific level is concerned. There are no time limits for the event. Solely depending on the demand for the particular item the event of reaching the reorder level may take place at any time. On the other hand with the fixed time period a predetermined time becomes the key for triggering up the mode. The order are placed at the end of a predetermined time. The time in between plays a vital role here.

The fixed quantity model is considered as a perpetual system where the withdrawal from the inventory or just an addition to the inventory would be regularly updated and recorded. These updated records would help in knowing whether the reorder point is accomplished. In order to reach the fixed order quantity regular monitoring of the inventory that is remaining is needed.  Whereas, in the fixed time model, a counting would take place only during the period of review. 

The average inventory in the fixed time period is larger since it has to be protected against the stockout at the time of the review period. Since the average inventory is low in the fixed order quantity model, it would favor expensive items. Some crucial items like the critical repair parts would suit the fixed-order quantity model very much because there would be quicker response and a closer monitoring to the potential stockout here. More amount of time is needed in the fixed-order quantity model since it takes into account every withdrawal and addition.