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Old October 16th, 2020, 07:48 PM   #1
mike3475
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plant ethernet cable loose connection

Hi, expert:
we have one machine with 6 Sercos axis (kinetix6000) controlled by L71, there are 1756-M08SE and 1756-EN2T and one input module and one output module in the PLC chassis, got int rehome issue during the machine in operation, found one ethernet socket in the ethernet switch has loose connection ,this ethernet socket was plugged in the plant ethernet, so we plugs it into another good socket.
not sure that will solve this issue, does anyone know what will cause if the plant ethernet plug loose.
thanks in advance!

Last edited by mike3475; October 16th, 2020 at 07:58 PM.
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Old October 16th, 2020, 08:33 PM   #2
Maxkling
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After crimping the locking tab isnít bent back outward. That will cause a loose socket connection.
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Old October 16th, 2020, 09:16 PM   #3
mike3475
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i am sorry to mislead the question.
my question is what will happen to the PLC and any related to int rehome issues during the machine in operation, if the plant ethernet has loose connection.
thanks!
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Old October 17th, 2020, 03:52 PM   #4
mike3475
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to be clear my question:
see the attached pix for our ethernet switch.
port X16 is connected to the plant ethernet network, we found this port had loose connection, so what will happen to PLC and any related to int rehome issue during the machine in operation? of course now we plug the plant ethernet cable in good port X15.
Thanks!
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Old October 17th, 2020, 04:47 PM   #5
Steve Bailey
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Is "int" an abbreviation of "intermittent"?
What exactly is an "int rehome" issue? Do you mean that one or more axes fail to rehome when commanded? Or does one or more axes spontaneously move to the home position for no apparent reason?
When you say "rehome" do you mean one or more axes perform a homing routine where it (they) drive to the home limit switch and set the axis position at zero? Or does it mean one or more axes drives to its defined "home" position.

Personally, I would not expect a loose ethernet cable to have any impact on a multi-axis Sercos control network. That doesn't mean there isn't an indirect cause/effect relationship. The PLC could be programmed to do something if it detects a loss of ethernet communications.
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Old October 17th, 2020, 05:01 PM   #6
mike3475
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Thanks Steve for your reply.
the machine was in production ( in the running status in the phase manager). the machine intermittently stopped and then went in to rehome for all axis. this machine runs good for many years, never have this issue before.

Last edited by mike3475; October 17th, 2020 at 05:09 PM.
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Old October 17th, 2020, 05:32 PM   #7
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if we disconnect the plant ethernet cable from the ethernet switch, in this case we can't access the PLC from the ethernet, does the machine still run without it ?
I have never try that.

Last edited by mike3475; October 17th, 2020 at 05:43 PM.
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Old October 17th, 2020, 05:48 PM   #8
Steve Bailey
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It's quite possible. In fact that's the most likely situation. The PLC is certainly capable of controlling six axes and the outputs wired to the single output module without needing to be in constant communication with whatever is on the plant network.

But I know nothing about the way the system is designed beyond what you've posted.
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Old October 17th, 2020, 05:58 PM   #9
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the reason we connect to the plane ethernet is we just have one RSLogix 5000 license, we have the VM running RSLogix5000, so we can remotely access the any PLC through it.
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Old October 17th, 2020, 07:30 PM   #10
Steve Bailey
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The PLC does not need RSLogix connected to run its program. You use RSLogix to create a program, to modify it, and to monitor operation when necessary. If the only reason for the ethernet connection is for remote monitoring via RSLogix, I doubt the loose connection has anything to do with the intermittent rehoming. Emphasis on the word "only".
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Old October 17th, 2020, 10:00 PM   #11
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now i am not very sure whether the plant ethernet cable has another purpose. next Monday I will disconnect the plant ethernet cable for 8 hours during the production, if the PLC working fine, no doubt the loose connection for plant ethernet cable is not cause for int rehome issue during the machine in the production.
i will post the result.
Thanks Steve!
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Old October 23rd, 2020, 12:59 PM   #12
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possibly found the problem was one servo motor's coupling a little loose, running good for 4 days after tightened it.
very sure that the cause is not form loose plant ethernet cable, after we disconnect plant ethernet cable, the PLC is running good, but HMI stops working, since this HMI (created by microsoft visual C#) is a OPC client, we have a OPC server running on a VM, we use KEPServerEX V5.0.
after careful read the PLC program, found that there is the force rehome all command after PLC detects any axis actual position out of the max tolerance value.
Thanks!

Last edited by mike3475; October 23rd, 2020 at 01:20 PM.
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