The machine-tool standards question. Both claim the shop floor, and several controllers now expose both simultaneously.
| MTConnect | OPC UA | |
|---|---|---|
| Specification | ANSI/MTC1.4 | IEC 62541 |
| First published | 2008 | 2008 |
| Transport | HTTP, XML documents | TCP binary on 4840, or HTTPS |
| Data model | A machine-tool semantic dictionary. DataItems classified as Sample, Event or Condition, with defined types and units. | A full information model: typed nodes, references, objects, methods and historical access. The richest model in industrial automation. |
| Discovery | Yes — /probe returns the full device model before you read a value. | Built in. Browse the address space, read the type definitions. |
| Security | None in the protocol. Read-only by design, usually kept on the plant network. | Built in and mandatory to configure: X.509 certificates, signing, encryption, user authentication. |
| Polling or subscription | Polling with sequence numbers, plus long-poll streaming from /sample. | Both. Polled reads and subscriptions with monitored items and dead-banding. |
| Implementation complexity | Low to moderate. It is HTTP and XML; the agent/adapter split is the only real concept. | High. The stack is large, certificate handling is a real operational task, and server implementations vary. |
| Typical industries | CNC machine tools, almost exclusively. Its vocabulary is metalcutting. | Modern machine tools, robotics, packaging, anything specified after ~2015. |
| Forge support | Adapter shipped. 21 OEM families mapped. | Adapter shipped. 23 OEM families mapped. |
Strength. The only protocol here that ships an opinion about what a machine tool means.
What it costs you. Read-only, machine-tool-specific, and the vocabulary is a floor not a ceiling — vendors add their own DataItem names freely.
MTConnect adapter →Strength. Self-describing. You can walk a server you have never seen and learn what it holds.
What it costs you. Self-describing is not the same as standardised — two vendors model the same machine differently, so the names still need mapping.
OPC UA adapter →MTConnect knows what a machine tool is; OPC UA knows how to describe anything. If every asset you care about is a metalcutting machine, MTConnect's vocabulary saves you work. The moment a robot, a washer or a CMM joins the cell, that vocabulary stops and OPC UA's generality starts to matter.
Forge is not an argument for a protocol. It is the layer that makes the choice stop mattering downstream: 16,908 curated mappings across 14 protocol adapters, resolving to 366 canonical fields with enforced units and physics bounds.
Two devices, two protocols, two vendors, two entirely different tag names — and one canonical field out. Both of these are real mappings from the corpus, not illustrations.
Same field: feed_rate. Same unit contract, same physics
bounds, same shape. Your query does not need to know which protocol the reading
arrived on.