Layout problem for an aricraft maintenance company tool room

A tool room of an aircraft maintainance company with 10000 tools is considered. These tools are borrowed by the mechanics when needed and must be returned before the end of shift. About 400 in-out transactions are handled by the storekeepers of the room. However, since the room is usually crowded with mechanics at their shift start/end times, the storekeepers are overloaded and significant productive manpower is held up in waiting for the tools. Therefore, the racks and tools in the tool room are required to be rearranged so that the handling time of the in/out transactions can be reduced. The racks are rearranged by heuristics and then tools are allocated to the racks according to request probabilities, which are estimated by the proportion of each tool’s on-load frequency during December 1992. Effectiveness is measured by comparing the total rectilinear distance travelled to fetch the tools requested during 11-15 January 1993 based on the proposed changes, to that based on existing rack and tool arrangement. It was found that improvement by tool allocation according to the request probabilities could reach up to 39% with the existing rack arrangement. Furthermore, minor rearrangement on the racks could also reduce the distance travelled by 12%.