CompactLogix serial number issue

I have 4 identical machines, each with a CompactLogix 1768-L45 with firmware v20.11 and identical programs with the exception of the processor serial number. In none of the programs is the option to "Match the project to the controller" enabled under the Advanced tab, yet each time I open the project and go online with any of the machines other than the one where the serial number matches in the project, I have to upload the project. If I save the uploaded project with a different name and then use the Compare tool, the only difference reported is the serial number, but all the logic and tags are identical. Does anyone else experience this? Is this a firmware glitch?

Thanks in advance for any assistance.

Jeff

I wouldn't think of having one program for 4 different machines even if they are identical. I have a customer with 8 identical machines but each project file name identifies which machine it is for. If an I-O card ever fails and is replaced with a newer version for example then your single project wouldn't match all 4 machines.

You raise an interesting point, but the issue I have is that these machines are portable. The rooms where these machines are set up and connected to the network are equipped with routers that are configured with port forwarding. This allows all 4 machines to have the same IP address so that they can be moved to any of the rooms and connected, and then communications to them is via the IP address of the router, not the PLC. In other words, there is no way for me to distinguish from one machine to the next based on PLC IP address, only serial number.

But you are correct that the hardware issue presents its own challenges, and an upload each time may be my only option. The last thing I really wanted to do was have to maintain 4 separate copies of the same program with identical logic and tags, but unless someone has another idea, that may be what I have to do.

I'm in agreement with having four separate copies, even if they are identical, simply because someday there will be a difference and at that point you need separate copies.

But beyond that, there are other good reasons to identify and track machines separately; asset identification / control and maintenance tracking are a couple. A component will fail and be replaced with a new one on only one of the machines. The same component on the other machines remain intact for years longer. The next time this component fails the question comes up - was this the new part failing prematurely or one of the originals? What if one machine gets hit by a forktruck and needs major repair - which machine was it? Lots of data is lost when multiple machines are lumped together.

In all, the headache (minor IMHO) of keeping track each machine and its own program separately is well worth the trouble.

Steve