PLC user program preparation PLC user program should be carefully scrutinized, not only to ensure the correctness of the logic control relationship, but also to consider reliability, and on this basis, it should be made more readable, so that in the future The electrical maintenance of the machine tool is convenient. Maintenance personnel should be proficient in the STEP-5 language and be able to use it to properly analyze the source of the fault and its cause. PLC User Program The PLC user program is programmed in the STEP-5 programming language. The components are as follows: Organization Block (OB): is the interface between the system program and the user program. Block (PB): is the part of the program written to the process for the structuring of the user program.
Application example: A SINUMERIKSPINT8T system grinder in our unit, after the grinding wheel is trimmed, the program will not run down. The characteristic of this fault is that there is no alarm display. After carefully checking the NC and PLC programs, it is found to be an operation error, which is caused by the position of the key switch. It can be seen from this example that the fault caused by improper operation is not a real fault, but a false fault, which can be classified as a fault that fails to meet the constraint condition (if the tool change command is not executed, it is found that the pneumatic drive robot or the tool changer In the case of the device, the pressure of the gas filling is not enough, and the operation process does not push the closing door into place, causing the machine to stop malfunctioning, etc., which are all such). Example: A CNC lathe is equipped with Siemens 8M system, and its PLC part is S5-150KPC, which causes downtime after a failure.
When the PLC is cleared, the red LED is still on, and the EPROM sub-module of the user program is removed. After the PLC is cleared, the LED green light of the PLC is lit, thereby judging that the fault is related to the sub-module or the user program. Check that the submodule is normal with PG675. After inserting the 350 memory board, the PLC will still stop running. Check the cause of the PLC fault with the interrupt stack ISTACK, which is the ADF (address error). The detailed interrupt indication indicates that the PLC is stopped in the next sentence of the PB21 block = Q18.20 statement, indicating that the error occurred in the =Q18.20 statement. Check out the output board where byte QB18 is located, check the address jumper, and confirm that the address setting is incorrect (user has changed this board). After correcting, the PLC operation returned to normal.
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