Put-Away and Retrieval Optimization Strategies towards Reduction of Blocks Relocations in a Block Storage

Although it is recommended to store goods in a warehouse based on the principle of first in first out, it is still unavoidable to use block storage of storing, for example, long andbulky goods. If the major advantage of block storage in area saving is themost important, the companyhas to accept the removal principle of last in first out or in other words, first in last out. The last goods to be stocked are the first goods to be removed and the first stocked goods are the last to be removed. There are some special observations in the block storage concerned in this paper. The first one is that the goods in the storage ordered by the customers can often not be removed directly from the storage without any stock movement. Theaim is to not only benefit fromthe high-density storage solution but also decrease the negative influence of block storage, especially when pre-stocked goods must be removed at first. The second observation is that during one concerned time period, forexample, one day, there may be several operations of put-away and several operations of order picking for shipment preparation. The third observation is that before goods are put away to storage, which goods to be removed are not always predictable. The preplanned removal dates are quite often unexpected changed. In this paper, scenarios with different dynamic properties and stochastic probabilities have been concerned and defined. Strategies for the three main stages of put-away, i.e. stacking, pre-marshalingand retrieval are defined and examined developed. Simulations have been conducted to examine the strategies based on different scenarios. The aimis to select the right strategy which may reduce the overall relocation operations. It is expected that the sum of blocks movement during put-away i.e. stacking, pre-marshaling, and block retrieval is optimally minimized.