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840D PLC can not 'Stop Force'

Created by: ahai at: 5/12/2009 6:19 AM (12 Replies)

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5/12/2009 6:19 AM	Rate (0)
ahai Posts: 1 Rating: (0)	Hi, For CNC machine troubleshooting, I forced a digital Input point,but I cant not stop this force by 'Stop Force' command in the menu.There are still this input point in the force table and PLC still display 'Force' state (the PFO LED always yellow). How can I stop/delete this input force? Thanks!
ahai Posts: 1 Rating: (0)
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5/12/2009 8:19 AM	Rate (1)
sandeep reddy Posts: 92 Rating: (7)	if you have done a force to a input : ex. m14.0 ---> forced to 1. now to get it back m14.0 ---> force to 0. this is the process to be followed.
sandeep reddy Posts: 92 Rating: (7)
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6/4/2009 4:47 PM	Rate (0)
Jason. Experienced Member Joined: 7/13/2008 Last visit: 1/16/2025 Posts: 107 Rating: (9)	The programming manual indicates that the force light will remain on once a force job is ran. My Opinion - understand the program and troubleshoot why it suddenly stopped working, never force. At most modify variable, because at least the plc has the opportunity to correct the state. This force light should let the plc programmer know that the plc is possibly in a state that the PLCprogram may not know how todeal with. Keep in mind, S7300/400 systems are found on much bigger installations that the typical small plc, and the result of a force job can be very catastrophic and hard to troubleshoot.I am very wary when I visit a machine that has the FORCElight on. My first priority is to get the PLC into a state that has not been tampered with. The plc programmer may or not be maintainence minded, so troubleshooting using the FORCE variable should be avoided. It is unlikely that you will see the builder of the equipment or the service groups use the FORCEfunction to fix a machine.

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6/5/2009 5:49 AM	Rate (0)
RAM81 Silver Member Joined: 3/3/2008 Last visit: 10/5/2023 Posts: 333 Rating: (52)	HI find the attachment this could help you regards Ram Attachment PF0.pdf (600 Downloads)

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6/16/2009 6:29 PM	Rate (0)
Bennydel Posts: 39 Rating: (0)	ahai Hi, For CNC machine troubleshooting, I forced a digital Input point,but I cant not stop this force by 'Stop Force' command in the menu.There are still this input point in the force table and PLC still display 'Force' state (the PFO LED always yellow). How can I stop/delete this input force? Thanks! We have the same problem, what did you do to solve it? We did a "UNFORCE" command from different PC's (MPI, Profibus, netwerkconnection)but the force stays active. We also did a warm restart and en complete power shutdown without result.
Bennydel Posts: 39 Rating: (0)
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7/15/2009 7:06 PM	Rate (0)
Niddi Posts: 1 Rating: (0)	Hi, I have the same problem: I forced an input and now i can't unforce it, please can someone help us?
Niddi Posts: 1 Rating: (0)
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7/20/2009 12:50 AM	Rate (0)
Jason. Experienced Member Joined: 7/13/2008 Last visit: 1/16/2025 Posts: 107 Rating: (9)	The force light remains on until you clear the plc, then reload it on most S7-300's, on S7-400 the light turns back off when done forcing ( I could be wrong here). I consider it a big red flag. Modify variable can be transparent. Force is not the typical approach. With small ladder diagrams with just a few rungs, I see great value of a force that can be performed easily. With large programs, force is less of an advantage.

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9/28/2009 8:44 PM	Rate (0)
IcemanOrig Posts: 2 Rating: (0)	I had the same issue as well, in order to clear the force I had to delete all SRAM on the PLC by doing following the PLC reset procedure as shown below. PLC general reset including system data and diagnostic buffer Note To clear the entire SRAM contents of the PLC including the system data blocks and diagnostic buffer contents. The data can no longer be accessed and the system data blocks must be loaded again. 1. Turn PLC start-up switch (S4) to setting “3” (MRES) (Request general reset) ⇒ Red LED PS goes out and lights up again 2. Press “Reset” button (S1) or cycle power. 3. When character “6” appears on display turn switch S4 to positions “2” - “3” - “2” (STOP-MRES- STOP) ⇒ Red LED PS flashes first at a frequency of approx. 2 Hz and then displays a continuous light again 4. After the PS LED light up, set switch S4 to position “0” (PUN-P) ⇒ Red LED PS goes out again and green LED PR (RUN) lights up ⇒ Initial clear of PLC complete, PLC then goes to cyclic operation mode
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10/26/2009 6:29 PM	Rate (0)
WillB Posts: 2 Rating: (0)	A "Force" can not be undone in an 840D Powerline S7-3xx processor. As described in the previous thread, the PLC must be defaulted then reloaded.
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5/4/2015 9:51 AM	Rate (0)
0105BS8810~ Posts: 1 Rating: (0)	The absolute easiest way to end a force with the 840D is to reload the PLC archive. This stops, clears, and reloads the PLC program automatically.
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