Esplain this to me please Mitsubishi PLC

Greg7683

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Join Date
Jun 2018
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Plainfield IN
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355
Ok all the wiring and connections are good photo eyes are new and all sensors are good and connected.


I have a transfer that wont lift up to send the unit to another conveyor. All the sensors are reading in the PLC the only way I found to get the transfer to work only once is after I right the program to the PLC and push the run/stop switch to run the transfer will lift up and transfer the unit but it will stay up and the belts just keep running I would have to reset the line to get it to stop after that the transfer stops working again.
 
Program is likely at fault. are you latching vs pulsing a movement sequence? Without being able to see the program there is little we can suggest as we have no clue what the permissives are per action to get things to go forward.
 
Unfortunatly I do not have Mitsu software, only AB. But perchance someone will come along who might have an idea, and that will help them if they choose to look into it.

Basic thing to do is go through your logic working backwards, find where you hang, check every single thing associated with it. Whats holding it back?
 
Well, it's hard to do this troubleshooting like this. We can only give wild *** guesses even if we can open the offline program.

Is the output turned on when it supposed to? Is there a mechanical malfunction? Does the output work when you forced it?
 
One should ask.. has this process run before without problems. If so what was changed?

If all your I/O is working 100% correct, its in the program. You'll have to move it from position to position along the line and see what is not allow each troubled rung to go true. Some input or output may be handled inverted when it shouldn't be. an XIO may be an XIC, etc. OTE may be an OTL without an accompanying OTU. so much can cause a process to halt that it needs onsite investigation while its running.
 
it is a program that worked for 4 years one day it just stopped working with that transfer I tried a new PLC and copied the program from another line since it is the same program. And the output that is x13 doesn't light up when it is supposed to I ran down all the cables and connections all that is good and the sensors all light up when I monitor it in the program. Why would it only work once right after writing to the PLC and pushing the stop switch to run then not work again that seem kinda wearied
 
something may be blocking or tripping a sensor that you haven't seen. It may show a input signal.. and sure that means your getting feedback. But if that signal is only meant to be true momentarily as the carriage passes and not stay true you may have a object that is causing the sensor to always read true. which can affect your outputs as the logic may not permit action at that point.
 
if this is a relay output, make sure you have your power to the common terminal that will supply it, if your output does not indicate any power out , check also with a volt meter. if no power out, your input devices may be bad, may need to flag them and check each one, can you go online and monitor the logic.?
 
do you have the right type of PLC? (sink/source)
do you have your PLC in RUN mode? (small switch, position depends on type, but it's close to data cabel plug)


also there is no chance i can read through 4000+ step of uncommented ladder :(
 
Yeah when they wrote it they didn't put any comments in and it is 0V for the output's Can you explain on how it should be commented like say they have PX036 as a photo eye in the middle of the transfer to I guess let it know it is time to lift up.
 
no comments.. ouch. IMpossible to figure out the remotely like this for free. Someone would charge out the rectum to do that one.

Anyway...

If your output is 0V when energized then you may have a power problem. Track those wires. Ensure nothing is damaged there. you should have a voltage reading when energized. Whether its 24vdc,120/240vac will depend on what your supply power is and what the PLC is made to handle on those contacts.


They may have commented it but not all PLCs retain comments when the program is loaded to it. Find the offline copy that has the comments and it will help yiou troubleshoot it immensely.
 
Nope there was never any comments I had someone com in in the past too help wit a few problems they even said they couldn't find any comments. So how would I comment on this stuff does any one have some examples on how it should be commented like say they have PX036 as a photo eye in the middle of the transfer to I guess let it know it is time to lift up
 
Comment it how you think it makes sense. The way my company does it is the Physical IO is mapped to Tags, the Tags carry the name that says what/where it is. PE_Tfr2Middle


PhotoEye, Transfer 2, Middle. we also then have PE_Tfr2Near and PE_Tfr2Far

Your rung comments should say what the following rungs do, you don't necessarily need to comment each rung,it helps to comment the first rung in a group so others know what it does. short and concise.
 

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