Posted 15 Apr 2023 Hello, My plant has a Stretchwrap Machine that has a CJ2M 11 containing a standard ladder diagram programme, a SFC and four Function Blocks. I have enclosed the programme. Randomly we are experiencing pallets behaving erratically on the conveyors and strange events on the wrapping turntable. the sensors all look okay so I am wondering whether the programme is randomly causing the SFC section to give an errant signal. I am thinking of upgrading our PLC to a CJ2M 13. Has anyone had experience of anything like this? Im maybe clutching at straws because my engineers cant see anything obvious. Regards Peter Stretchwrap_CPU11140423.cxp Share this post Link to post Share on other sites
Posted 17 Apr 2023 I don't think there is anything wrong with the CPU. I would check the relay output cards first. Are they driving the contactors directly? It should be easy enough to move the motors to spare outputs. Share this post Link to post Share on other sites
Posted 18 Apr 2023 I have looked in your program. And my consern is that you are using direct sensors inputs in your program for detecting if there is or is not a Pallet . and using these sensors for resets to . DO NOT USE A DIRECT INPUT. You catch them with a KEEP and Reset the Keep with TIM of Off delay. Why ? Many times sensors wil miss stuff or flikker on and off in conver systems.I can you imagin what happens if a sensor flikkers in your program . you should catch the signal there is a pallet and the status can only change when there is movement wanted from one to the other. if you are not sure just put a counter on all your sensors that detect the palets . They should all be in sink if the last pallet leaves if they do not have the same count or about the same count the question is witch one and why ? Second thing to check your I/O cabels , you will not be the first that has problems with induction. When a motor starts parts of your I/O light up like a cristmass tree i have had that a few times in the past where motor and signal cables where in the same part of the board . Share this post Link to post Share on other sites
Posted 18 Apr 2023 Thanks for the replies and certainly food for thought. I will replace the three Output Cards that we use. We inherited the programme and in fairness we didnt have much trouble with it until recently. We will also put a counter on all our conveyor sensors as advised. Many Thanks Share this post Link to post Share on other sites
