Development of Storage Allocation Models in a Warehouse

Abstract

The developments in warehouses have significantly influenced the existing paradigms in inventory research. Unfortunately, the attention paid by researchers in inventory theory to the management of storage systems such as warehouses has been relatively limited. Often, it was considered mainly to be a technical issue and therefore belong to a different area, i.e., material handling research. The warehouse problems can be classified mainly into two groups i.e., the design problem and the operational problem. The design problem deals with the issues such as over all structure, sizing and dimensioning, department layout, equipment selection, and operation strategy of the warehouse. On the other hand, the operational problems deal with receiving and shipping, and storage and retrieval (order picking). Chapter 2 provides a brief description of the literature related to operational problems. Maintenance environment warehouse is very similar to production warehouse where spare parts are stored and retrieved. In such an environment, allocation of space and assignment of spare-parts in a warehouse is a vital problem for sound operation of a warehouse. Miss-allocation of spare-parts takes huge time to find out parts. This problem causes extra time consumption and money expenditure for the involvement of labor for long time and creates risk of unavailability of spare parts that lead to improper maintenance or repair of machines. Generally, allocations of items are done in alphanumerical order without regard to issue frequency, size, weight or volume. As a result, it will be creates problems in issuing/retrieving the spare parts with minimum waste of time & effort. The objective of this research is to study the developments of operational problems related to production warehouse especially for maintenance environment. Chapter 3 is devoted to develop an efficient methodology to identify the similar parts i.e., sparepart_set (SPS) that can be grouped together and be kept in one place. Doing so, it may increase the efficiency of the storage and retrieval. The weight (popularity index) is used to identify the Spare_part_set as slow moving or fast. The weight of a spare_part_set is the summation of all item's frequency of usages in year. By considering weight, higher weight SPS (fast moving) should be kept near to issue counter and less weight (slow moving) SPS is to be placed far from counter.

In chapter 4, the model is simulated for hypothetical warehouses. The objective of the experiment is to investigate the performance of the methodology described in the previous chapter in terms of travel distance to collect all the items of a demand. For this purpose, three hypothetical warehouses are considered. The first one, in which the spare parts are stored in alphanumerical order and the second one, in which the spare parts are stored according to the algorithm described in chapter 3 and in the third one, spare part are stored randomly. The details of the experiment and the results of the experiment are presented in chapter 4. The performance of the algorithm is evaluated in terms of the average travel distance needed to collect an order of SPS. It is found that the average travel distance is minimum (20%) less for our proposed methodology. Lastly, in chapter 5, conclusions and some recommendations are presented.