Simulation of Automatic Output Operations for Rice Seedlings

In Taiwan, more than 800 seedling nurseries prepare rice seedlings to be sold for paddy production. Operations relating to seedling production require significant levels of labour, especially when harvesting the seedlings. A new seedling removal system has now been developed to automate the seedling output process. The system has been modified from and integrated with several previously developed units, namely, the seedling tray-loading machine, conveyor, seedling-mat rolling machine, seedling-roll relocating machine, and seedling-roll stacking. The performance of individual units and the collaboration between these units are important in affecting the overall efficiency of the system. An animated simulation model was developed to conduct an analysis on the output operations for rice seedlings. With this model, the working efficiency and the system throughput under different operational conditions were studied. It was shown that the optimum operational pattern could be found by adjusting the length of working row and the operation rates among units. A row of 30 m in length, for example, has been examined to obtain its maximum system throughput of 1288 trays h−1, under a tray-loading speed of 0·3 m s−1, a tray conveyor rate of 0·46 m s−1, a rolling rate of 5·5 s tray,−1 for the seedling-mat rolling and a seedling-roll relocating rate at 2·3 s tray−1. Under these conditions, the utilisation rates were found to be 86% for the tray-loading machine, 65% for the seedling-mat rolling machine, 81% for the seedling-mat relocating machine, and 65% for the stacking workers, respectively.