Classic OPC UA already solved a real problem. OPC UA is a vendor-neutral way to read a controller. It got that view into SCADA, the plant screens and alarms; into MES, the system that tracks production orders; and into historians, the databases that store machine readings over time. It did not replace the networks already on the machine: EtherCAT, PROFINET, POWERLINK, or EtherNet/IP. Those are the fast networks brands use to reach drives and sensors. OPC UA FX (Field eXchange) is the OPC Foundation’s attempt, under the name Field Level Communications, to extend that same description down to controllers talking to each other and, later, to drives, inputs and outputs, and other devices on the machine. Inputs and outputs are the sensors and the devices the controller turns on and off. The aim is to do that without inventing yet another private network.
How to read this Written for machine builders and plant teams. Specification numbers and certification lists move. Treat the OPC 10000-80 series, and each vendor’s current statement about the exact catalog item, as the source of truth for a given build. A SKU is that catalog item. For Festo’s current valve, input/output, and controller hardware — a separate story — see Festo’s 2025–2026 developments.
OPC UA got data out of the controller. OPC UA FX is the attempt to put the devices on the machine onto the same language, without pretending today’s machine networks disappeared.
The problem FX is trying to solve
On the plant-screen side, OPC UA is a success. Controllers and industrial PCs expose tags, the named signals; methods, actions you can call; and alarms, in one shared map of names. An industrial PC is a hardened computer built for a cabinet. On the machine, the inputs, outputs, and drives still speak a real-time network that favors one vendor:
- EtherCAT on many Beckhoff and multi-vendor motion cells
- PROFINET (often IRT) on Siemens-centric machines
- EtherNet/IP / CIP on a large share of US discrete plants
- POWERLINK on B&R machine islands
- Vendor backplanes and satellite protocols behind the bus node
Those networks work. They also split the installed base into camps. Controller-to-controller exchange still happens through custom signal names, Rockwell’s produced-and-consumed data on CIP (the protocol inside EtherNet/IP), or a SCADA system sitting in the middle. Device diagnostics get flattened into simple on-off maps and into a vendor’s add-on instruction, the packaged block of logic that brand ships. FX’s bet is one shared description of a device, an explicit connection between devices, and a path to Ethernet that stays on a fixed schedule when the job needs it.
What OPC UA FX actually is
OPC UA FX (also written UAFX) extends ordinary OPC UA down to the devices on the machine. The first specification set was released by the Field Level Communications initiative in November 2022 after several years of member review and prototypes. The steering committee included the usual automation majors — ABB, Beckhoff, B&R, Bosch Rexroth, Emerson, Phoenix Contact, Rockwell, Schneider, Siemens, Omron, Mitsubishi, and others — plus device and network vendors. The 2022 SPS trade-show demo put controllers from about twenty manufacturers on the same UAFX connection story.
Specification map
The documents live in the OPC 10000-80 series:
- Part 80 — Overview and concepts. The device description, the connections, and the patterns: controller to controller (C2C), controller to a device such as a drive (C2D), and later device-to-device or extra computing.
- Part 81 — Controller / information model. How a PLC, or a process controller of the kind used in a plant control system, presents itself as an FX participant. A PLC is the controller that runs a machine. A DCS is the distributed system that runs a process plant.
- Part 82 — Networking. How FX rides Ethernet. That includes PubSub, publish-and-subscribe, where a device sends data on a schedule instead of answering one request at a time; how addresses work; and the relationship to TSN, time-sensitive networking, which reserves the wire so important traffic is not delayed.
- Part 83 — Offline engineering and descriptors. How a machine is described before it is powered up, so startup is not a bag of IP addresses.
- Part 84 and companion profiles. How you prove a product conforms, and the profiles for classes of device (drives, inputs and outputs, and later more families).
The first public release focused on C2C, controller to controller. That is not a footnote. Most of the 2022 demo of different brands working together was controller-to-controller process data over UAFX connections and publish-and-subscribe. C2D, controller to device — a drive, an input/output rack, or a valve terminal treated as a real FX device — is the harder product problem. It is still rolling out one catalog item at a time in 2025 and 2026. B&R’s ACOPOS M4 and X20BC008T are early public examples shaped like C2D. They are not a reason to assume every vendor’s 2019 input/output hardware speaks FX.
The object model, in plant language
- AutomationComponent. A controller, drive, input/output node, or other participant that shows its identity, what it can do, its process data, its diagnostics, and the endpoints other devices connect to.
- Connection. A link you engineer, with a life cycle from setup to shutdown. It is a different thing from subscribing to a signal in SCADA. Connections come up when the system goes live.
- Connection Manager. The piece that calls OPC UA actions on each device and brings the configured connections up. It can live in a controller or as a separate box. Early demos used Connection Managers from Siemens and Unified Automation. Later software builds the role into the programming tool and the controller software.
Underneath, FX reuses OPC UA publish-and-subscribe for repeating process data, the existing security model (certificates, user logins, encrypted channels), and optional TSN when the Ethernet has to behave like a machine network. The TSN pieces named in the standard are IEEE 802.1Qbv, which schedules slices of time on the wire, IEEE 802.1AS, which syncs the clocks, and related profiles.
TSN is not FX, and FX is not TSN UAFX can exchange controller-to-controller data over ordinary UDP/IP Ethernet. TSN is the quality-of-service path when you need a known maximum delay on a shared wire. A TSN switch does not make a device speak FX. FX software does not make an unmanaged plant network stay on a fixed schedule.
How this compares with the buses you already have
| Network | What it is optimized for | How fixed the timing is | FX relationship in 2026 |
|---|---|---|---|
| EtherCAT | Dense I/O and multi-axis sync | A hard repeating cycle, with clocks shared across the devices | Still the motion network on most TwinCAT cells. TwinCAT is Beckhoff’s control software. FX sits beside it or above it |
| POWERLINK | B&R machine + ACOPOS-class motion | A hard repeating cycle, with a managing node assigning a time slot to each device | B&R is adding FX controller-to-controller and controller-to-device as an open path, not a rip-and-replace |
| PROFINET IRT / RT | Siemens machines and plants | Isochronous mode when the timing has to be hard; a looser real-time mode otherwise | The plant standard stays. FX is the story for controllers from different brands talking as peers |
| EtherNet/IP (CIP) | US discrete cells, Rockwell stacks | Scheduled input/output on CIP, the protocol inside EtherNet/IP; CIP Sync when axes must share a clock | Do not throw it out. FX is interesting when a Rockwell controller must talk to a machine from another brand |
| OPC UA (classic) | SCADA, MES, recipes, diagnostics | Fine for screens and reports, unless you deliberately engineer publish-and-subscribe and TSN | Still the right first step on almost every machine |
| OPC UA FX C2C | Controller-to-controller Connections | Publish-and-subscribe; TSN is optional | The mature part of the spec. Ask for each controller’s software |
| OPC UA FX C2D | Open drive / I/O field devices | A repeating cycle at device level, plus security | Still emerging. Verify the certificate for that exact catalog item |
Security and operations
Older machine networks often treated the cabinet network as a trusted island. A fieldbus is that network to the drives and sensors. That assumption is dead in any plant with remote machine builders, shared Ethernet, or an insurance questionnaire. OPC UA’s certificate model, which FX reuses, is one of the better answers the industry has.
The catch is operational. Keeping certificates alive on a 40-device machine is real engineering work: issuing them, renewing them, backing up the Connection Manager, and a plan for replacing a device at 2 a.m. If your team cannot run that process, you are not ready to make FX the motion network. You may still be ready to use classic OPC UA for the data that goes to the screens.
Functional safety, the certified way to stop the machine safely, is a different family of standards. Safety over EtherCAT (FSoE), PROFIsafe, CIP Safety, and openSAFETY do not become “solved” because the repeating data channel is encrypted. Design safety on purpose.
What to put in a specification
- Which claim is on the table: classic OPC UA, FX controller-to-controller, or FX controller-to-device? Sales decks collapse these three sentences.
- The exact catalog items, the firmware, and the UAFX certificate or the date they say it will be certified.
- Where the Connection Manager lives, and what happens to the connections if that box is down.
- Whether safety rides the same wire or a separate safe network.
- How FX lives next to the machine network you already have. Running both is a product you have to buy and test. It is not a slide.
- For US plants: how the design sits next to EtherNet/IP, CIP Safety, and the controller brands the plant already prefers.
What not to do
- Do not rip out a working EtherCAT or EtherNet/IP machine because FX is the conference theme.
- Do not treat a parts list of TSN switches as a design.
- Do not skip naming the data. If you cannot name the diagnostic you want in the historian, FX will not invent that engineering.
Orgenis view for 2026
Put classic OPC UA on the controller or the small computer at the edge of the network so machine data is not trapped in one vendor’s private data type. A UDT is that private bundle of signals. Treat OPC UA FX controller-to-controller as a real purchasing question where two controller brands must talk without a custom list of signals. Treat controller-to-device as specific to the catalog item, and still emerging.
If you are selecting a machine controller, see B&R vs Beckhoff. If you are on Festo pneumatics and I/O this year, start with the current Festo platform changes — those products ship now; FX on the valve slice is a later question.
Orgenis can review a mixed-vendor cell and write a decision memo that separates what you can ship this quarter from what belongs on the next platform revision.
Discuss an OPC UA FX or mixed-vendor machine-network architecture with Orgenis.