Due to the continuity of forging production, the transportation of the system cannot be continuous, therefore, there is a high demand for the operation and maintenance of the entire system transportation line. The driving equipment of the belt conveyor in the pouring line system is all oil cooled electric drum. According to the process flow, the control requirements of the belt conveyor are: (1) the ability to choose any process, and the working mode can be manual, automatic, on-site, etc. (2) The normal start-up and operation of any process should follow the reverse sand flow direction and delay the start-up sequence one by one. (3) When shutting down normally during operation, delay the shutdown one by one in the direction of sand flow. (4) If a conveyor malfunctions and shuts down during operation, downstream equipment will operate normally, while upstream equipment will shut down normally. (5) Real time monitoring of transportation line equipment and display of operational status.

The controlled equipment in the sand processing department is interrelated, with multiple signal points, long signal transmission distances, and harsh operating environments. Therefore, PLC was chosen as the control center for this department. The PLC from Hitachi's EM series is used for the operation of the belt conveyor from command to output. The C40P programmable controller is used for the inspection of the operation status of the belt conveyor, and it is used as an independent inspection unit for signal interlocking with the upper computer. The development of the transportation program for the molding sand process follows the principle of real-time control and is based on the process flow to develop the fundamental program blocks. According to the control requirements, the belt conveyor is started in the opposite direction of sand flow. After the process and working mode are selected, the system is started according to the prepared program. 5P means that after starting the belt conveyor, after a certain delay and speed check, 4P is started and so on. If the tape of a certain conveyor slips or has other problems, the inspection component will send a signal to the PLC, exempt the interlocking link in the program, suspend the corresponding conveyor line, and avoid sand accumulation.

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