When designing a production-line data gateway, the decision almost always comes down to these two protocols. We deploy both regularly — the choice depends on the usage pattern.
OPC UA: the structured industrial standard
The OPC UA information model is rich: types, hierarchy, metadata. For MES/ERP integration, where the consumer wants to browse the device's data model, it is the natural choice. The Kemppi AX and most robot controllers provide it natively.
MQTT: lightweight telemetry
The MQTT publish/subscribe model beats everything towards the cloud, with large device counts and on weak networks. We use it for SCADA dashboards, OEE calculation and alarms — with Sparkplug B the payload is standardised too.
In practice
A typical Neuraweld installation has both: OPC UA inside the cell (robot, PLC, power source), MQTT from the cell upwards (dashboard, cloud). The gateway bridges the two.