Simulation of conveyor transport operations using a gantry system

The gantry system has been widely employed within rice seedling centres in Taiwan to transport planting boxes. The objective of this study was to develop a computer model to simulate this process by evaluating two transport activities in four seedling centres in Taiwan. In the first, the seeded boxes are moved to the field for sprouting. In the second, boxes of seedlings are moved from the field for transplanting. The throughput performance and worker efficiency of each centre was measured and compared. Variables include field shapes, operation methods, and number of labourers. The predicted values agree well with observed values. The model shows that a poor allocation of labour force leads to an imbalanced workload, restrictions in the workflow and decreased system throughput. Optimum operating efficiency occurred in simulation where seven labourers worked on both sides of a gantry, in fields 7.6 m in width. Peak simulated throughput reached 3716 seeded boxes per hour moving into the nursery field and 2155 boxes of seedlings per hour moving out of the field. Installation costs were higher for the longer gantry operations. With fields of identical size, hardware cost for the 200 m gantry was 39.5% higher than for the 100m gantry, and 47% higher than the 50 m gantry. (C) 2000 Silsoe Research Institute.