Stacker crane for material handling

Abstract

Stacker Cranes CSC) differ in harmony with their application and material to handle. Basically, they all have the same main features. They are animated through linear motion in 3 Cartesian axes, operating in a rectangular work space. The function of any type of SC, is to handle items on pallets within a multi-level array, through the aisle. Basically, a SC consists of a pillar structure which operates through the aisle. The base or root of the pillar structure moves on a rail along horizontal ground, while an overhead rail keeps the pillar steady. A carriage travels along the pillar to achieve motion in the vertical direction. This carriage accommodates an actuator which provides motion in the lateral direction. This actuator is either an extendible shuttle table or telescopic tongues, depending on the application or items to handle. Their size may reach a height of 5 storeys. Usually these operate in an environment purposely designed. Originally, these were developed to replace the traditional forklift trucks. Although their main application was to handle material in closed environment warehouses, they are also incorporated Within Flexible Manufacturing Systems (F.M.S.). Warehouses which operate with these units, may reach three to four times the storage capacity of a conventional warehouse for the same floor space. This improvement enhances the application of SC type system. On using SC, the aisle between stacks is narrow as much as the width of the pallet. This means that a large ground area is exploited for storage while a smaller floor space is used for material transportation. The SC design configuration, a high pillar remote controlled structure can handle materiel to high levels above the ground, which normally are inconvenient to adopt for human operated forklift trucks. This results since in the latter case, the operator has visibility handicap, he has difficulty to locate the lifter forks into right position when handling material at high levels. So, on using SC, on same floor space, there is a tendency to employ high bay racking. Whether using this type of system or the conventional one, storage is an overhead expense with low return on investment. The selection of the system to adopt depends on the level of storage capacity in relation to financial and other concepts. SCS adoption is enforced by the modern idea of automation in all fields of manufacturing systems. As in all automated systems, the basic advantages are higher operating rates, reducing hazardous material handling, eliminating the presence of human beings from stacking zone, reducing labour force, and its computerised control can provide data collection. The data collection serves to update the store register and records the SC's operation sequences. Although SCSs were developed for automated stacking in warehouses; further development allowed for application of these units in FHSs. These were used to replace AGVs, since the latter operate in a singular level. An in-line controlled SC, handles pallets with different in-process material, tools or equipment at various elevations. The SC transfers items from locations to their respective destinations in harmony with the production process.