OPC UA — Industrial Communication Standard
OPC UA (OPC Unified Architecture) is the modern, platform-independent industrial communication standard that connects machines, sensors, control systems, MES and increasingly ERP. Defined by the OPC Foundation and standardised under IEC 62541, OPC UA succeeded the legacy OPC Classic specifications and underpins the Industrie 4.0 architecture in DACH manufacturing. For ERP-bearing manufacturers connecting shop-floor data to the business systems, OPC UA has become the de facto integration standard.
Architecture and key features
OPC UA defines two architectural patterns. Client-server: a server (typically embedded in a machine, PLC or gateway) exposes data; clients (MES, SCADA, ERP or analytical tools) connect and read or write data. Publish-subscribe (pub/sub): machines publish data to topics on a broker (typically MQTT or AMQP); consumers subscribe to topics of interest. Pub/sub fits IoT-scale scenarios with thousands of devices. Key features: information modelling (machines describe their data semantically, not just as raw values), security (built-in authentication, authorisation, encryption), platform independence (runs on Windows, Linux, embedded systems, real-time OS), scalability (from microcontrollers to enterprise servers).
Companion specifications
OPC UA Companion Specifications standardise data models for specific machine and industry categories. Notable examples: OPC UA for Machinery (umati — universal machine technology interface, driven by VDMA), OPC UA for Robotics, OPC UA for Machine Tools, OPC UA for Injection Moulding, OPC UA for Plastics and Rubber Machinery, OPC UA for Vision. Each defines a standard information model so that a machine of a given category exposes comparable data regardless of vendor. The umati specification from VDMA has rapidly become the standard for DACH machinery exporters and is increasingly mandated by industrial buyers.
Relevance for ERP and MES
OPC UA rarely connects directly to ERP. The standard architecture: machines speak OPC UA to an MES or IoT platform; the MES aggregates and enriches the data; aggregated metrics flow to ERP via REST or OData APIs. Direct ERP-OPC UA connections happen mostly in smaller operations without a dedicated MES, where the ERP's shop-floor module subscribes to OPC UA endpoints. Major MES platforms (Siemens Opcenter, Rockwell FactoryTalk, MPDV HYDRA, Werum PAS-X) include native OPC UA clients. IoT platforms (Microsoft Azure IoT, AWS IoT Greengrass, Siemens Industrial Edge, Bosch IoT Suite) act as OPC UA aggregators and translators between the shop floor and cloud-side analytics.
Practical adoption status
As of 2026, OPC UA dominates new industrial-automation projects in DACH manufacturing. Legacy installations with OPC DA, Modbus, EtherNet/IP and Profinet remain widespread — OPC UA gateways translate between protocols for transition periods. Adoption drivers: VDMA umati push for machinery exporters, Industrie 4.0 reference architecture (RAMI 4.0), digital-twin initiatives (Asset Administration Shell), and regulatory pressure for energy transparency (CSRD reporting at the machine level). Implementation effort for an OPC UA connectivity project: 50-300 person-days per factory site depending on machine-count and legacy-protocol mix. Cost: 50,000-500,000 EUR for typical mid-market factory.
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Frequently Asked Questions
Is OPC UA secure for production environments?
Yes — OPC UA includes built-in security with x.509 certificate-based authentication, signed and encrypted communication, and granular authorisation. Properly configured, it meets industrial security requirements including IEC 62443 alignment. Common configuration failures: unauthenticated 'Anonymous' access enabled by default, certificate validation disabled for testing and never re-enabled, or signing-without-encryption modes used in production.
Do we need OPC UA if we have Profinet or EtherNet/IP?
Profinet and EtherNet/IP are field-level fieldbus protocols connecting PLCs to field devices. OPC UA is an application-layer protocol connecting machines and PLCs to upstream IT systems. They are complementary, not alternatives. A typical factory uses Profinet between PLC and field devices, OPC UA between PLC and MES/ERP.
What about MQTT versus OPC UA?
OPC UA pub/sub increasingly runs over MQTT as the transport, combining OPC UA's rich information modelling with MQTT's scalability. Pure MQTT (without OPC UA) is simpler but lacks the standardised semantic model. For industrial IoT in DACH manufacturing, OPC UA over MQTT is the emerging default.