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. 19 verticals mapped. | Adapter shipped. 19 verticals 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: 2,086 curated mappings across 13 protocol adapters, resolving to 985 canonical fields defined 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.