RS5000 Time sync issues

Good Morning. I am fighting a time sync issue between two machines on the same network. One machine has kinetix 5500 servo drives, and the other has a power flex 527. I have a problem where if one machine drops off the network, the other machine will get a control connection fault on the servo, or the powerflex drive. I have been fighting this for a couple months now. To resolve the issue on the machine with the 5500 drives, I need to do a fresh download to get them back in sync with the PLC. I have played around with the master override, and tie breaker, but it just changes which plc is the grand master.

Is there a way to have each plc their own grand master, so they are not fighting each other on the same network?

The main issue last night was a fan was plugged into the same circuit as our plant network, tripping the breaker. When the network switch powered back up, we lost the sync on the other machine.

Any suggestions would be greatly appreciated.

Kenneth

We had this same issue a few months ago. Two machines with Kinetix servos. They were constantly "fighting" over who the master clock should be. Setting one or the other as having higher priority helped a little but as soon as one of the machines was turned off for cleaning it would fault out the other. The solution that finally fixed the problem was to put the machines on separate V-LAN's.

This KB article might be useful depending on your network layout. With our layout we could not try it.

Access level - Everyone https://rockwellautomation.custhelp.com/app/answers/detail/a_id/1028845

So, it sounds like you don't actually want them synced to each other but rather to free run.

One solution would be to put them on different networks.

Second would be to get a time master that is independent of either of them and have both synced to it but you still have a problem if that drops offline.

In PTP, there is a way to configure different domains at the switch level. This should allow multiple grandmaster clocks on the same network. Never done it, never heard of it being used (kinda defeats the purpose of syncing but might be what you're after).

Timbert said:

In PTP, there is a way to configure different domains at the switch level. This should allow multiple grandmaster clocks on the same network. Never done it, never heard of it being used (kinda defeats the purpose of syncing but might be what you're after).

Click to expand...

Timbert, Do you happen to remember where you read about this? Myself and my IT / OT guy put a fair amount of research into our problem and never came across this info. As I stated before, our fix ended up being VLANs. I works, but makes it harder to connect with the machines.

Thank you guys for confirming my suspicions. I am going to try and get our IT department involved to see what it will take to segregate the network some more. each of these machines have their own managed switches. One has a NTRON 716tx, the other a cisco rack switch. But I am not going to get involved with creating the VLans.

Thank you.

Installing a NAT on one of the machines, to keep the two machines separated should work as well right?

Our switch does not have NAT capability, so I don't know for sure, but my IT/OT guy tells me that yes NAT could solve the problem as well.

Lynx777 said:

Timbert, Do you happen to remember where you read about this?

Click to expand...

https://rockwellautomation.custhelp.com/app/answers/detail/a_id/1039646

and it points to wikipedia: https://en.wikipedia.org/wiki/Precision_Time_Protocol look for domains

I'm pretty sure this stuff requires command line configuration at the switch. Reference [no] ptp domain number

Thanks Timbert

kjacoby said:

Installing a NAT on one of the machines, to keep the two machines separated should work as well right?

Click to expand...

We had the same issue on two machines at my last job. Per Rockwell, (at least at the time) preferred options are:

1. Isolated networks
2. Separate VLANs
3. NAT on at least one of the machines

The switches we were using (Hirschmann RS20 managed switches) gave us some isolation, but we'd still run into instances where one of the machines would take over as grandmaster for the other. Once our corporate IT setup a VLAN for one of the machines the problem went away. We never tried the NAT approach.