VLAN clarification

Want to make sure I understand the concepts of introducing VLANs into a control environment. I have inherited a recently installed application where Ethernet time out messages are becoming an issue with EtherNet/IP Powerflex drives.
This application has 6 Compactlogix PLCs, 6 Ethernet/IP Flex IO drops, 30 EtherNet/IP PF523 drives, 2 PV+ HMIs. All devices are on the same subnet and there is another subnet that has an Ignition application with 4 Thin clients.

All 6 PLCs message to each other and all 6 PLCs own at least 1 of the FlexIO drops and at least 1 of the EtherNet/IP PF523 VFDs.

All Ethernet runs in the plant come back to a Stratix 5700 switch in the IT closet. I want to segment this network into at least 2 plant floor level VLANs and keep the SCADA network separate as it is.

Now, if i create 1 VLAN for VFDs & FlexIO and 1 VLAN for PLC to PLC messaging, HMI and programming on the Stratix 5700, does this mean each PLC will need a unique EtherNet communication port to connect to each VLAN?

Yes, 1 port per device per vlan. Is the SCADA system networking all of these PLCs? You could move the PLC to PLC comms there.

"Typical" installs utilize 2 isolated networks. One for I/O and one for peer-to-peer PLC comms and HMi/SCADA. Actually, each PLC has its own dedicated I/O network. This is done on large ControlLogix based systems. Your CompactLogix based system probably doesn't need as much infrastructure.

Check your update rates on the VFDs and I/O. Most operations don't require the low RPIs that are default.

Keep in mind VLAN's are more for isolation for security than they are for performance unless you are dealing with lots of broadcast traffic then they can be helpful somewhat for performance byt if you are dealing with lots of broadcast try to use unicast where possible and avoid multicast where you can.

From what you describe I would be checking connection limits on the equipment such as PLC's and checking for multicast and broadcast traffic.

If you don't have managed switches the managed switches with IGMP snooping will help more than VLAN's.

Check RPI rates and check physical layer issues "poor or wrong cable, bad connections, etc.

Also check port speed and auto negotiation settings.

I am happy to go through VLAN's with you but from what you describe I really doubt it will help at all and would just give you a more complex setup without gaining you a lot of value.

If you don't already have a good network map I highly recommend starting one and recording all the settings for each node as you check things and many times as you build this the problem will show itself to you on paper and will be a gret help to you are anyone else who services this equipment in the future.