Kinetix 5500 time sync fault

We have a machine with 3 kinetix 5500 servos that are daisy chained together. The final servo is connected to a switch and the switch is connected to the network. We are having the problem where the servos get a time sync fault 4 or 5 times a day and we have to reset the machine to clear the faults every time. We have another very similar machine except it is not connected to the network and the servos on it do not have any problems.



We are trying to figure out a way to either disable the time sync function on the servos or disconnect the servos from the network. The PLC (rslogix 5000) is plugged into the same switch as the servos, but it needs to be connected to the network. We cannot configure the switch to turn off the time sync. We were thinking about putting a NAT device between the switch and the network and not allowing the servos to communicate with the network this way, but I feel like there has to be an easier way and figured I would ask you guys if you have any ideas.

Check your network switch for IEEE-1588 Sync capabilities - if it doesn't support it, thats where your problem is.

I looked up the switch but I did not see anything about IEEE-1588 sync capabilities. The switch is Spider II 16TX EEC. I am not sure how often the servos try to sync? Is it possible it only does it 5 times a day and it can't do it because of the switch or does it do it many more than 5 and only fails to sync occasionally?

In the plc time synchronization is enabled, but the time in the servos is 3 hours ahead of the plcs time. I'm not sure if that has anything to do with it.

Its pretty important for PLC to Servo interaction, in fact if you were to disable the time synch on the PLC, IIRC, the program won't compile and download.

Read this from Rockwell

I'm no expert, just a user but in my experience, if the switch doesn't support it, unusual or bad things happen.

Not sure what PLC you are working with, but if it has 2 ports on it, like the 1769-L30ERM, plug the servo chain directly into the PLC's 2nd port, then you won't have to worry about whether your switch supports PTP/sync or not.

edit:
As I think about this, I'm doubting that the switch is the problem, considering the frequency of the problem. I'm going to venture a guess that there is some network configuration problems that is causing packet loss, FSC errors or something like that. If you can plug your chain into a spare port directly on your PLC, certainly do it. However, I'd be looking at your PLC's web page for any missed/rejected packets, % of network utilization, etc. I'm wondering if you'd see something else there that is causing the servo's to complain about the connection, since they are probably the most sensitive to packet loss.

We will try plugging the chain into the plc. The weird part is we haven't been having this issue from the beginning, it only started recently. It has been wired the same for the entire time.

Edit: the only real difference is we have started running the machine more lately

alanze said:

We will try plugging the chain into the plc. The weird part is we haven't been having this issue from the beginning, it only started recently. It has been wired the same for the entire time

Click to expand...

I would definitely take a peek at your PLC's web page too, check for any packet errors. For things like missed/rejected packets and FSC errors, the only acceptable value is 0.

edit: The thing with intermittent issues is, if the more you run, the more you'll see them

We plugged the servo daisy chain directly into the plc and the frequency of the clock sync faults went down but we still have had a few. Our other machine like this that doesn't have this problem isn't connected to the network and that machine's plc clock is set as the grandmaster. The problem machine is connected to the network and is syncing to a different plc's clock. Is there a way to change the grandmaster clock to the machine with the problem? I don't even know if that would fix the problem but it's worth a shot.