MTConnect: getting data off the machine tool

CNC controllers speak vendor dialects — FANUC FOCAS, Heidenhain DNC, MTConnect-unfriendly proprietary APIs — which is why "just connect the machines" turns into a per-controller integration project. MTConnect is the open, read-only standard that normalizes machine-tool data: one HTTP/XML interface describing what the machine is, what it is doing, and what it measured, regardless of the controller behind it.

FIG. 02From machine to data

Adapters, agents, and the data model

The architecture has two halves. An adapter talks the controller's native protocol and emits simple text observations (power on, mode automatic, spindle override 100%). An agent collects adapter streams and serves them over HTTP as XML documents: probe describes the device structure (axes, spindles, doors), current gives present values, and sample streams timestamped observations. The vocabulary is standardized — data items like execution, controller_mode, position, load — with controlled vocabularies for values, so "the machine is running" looks identical from every compliant agent.

MTConnect also defines assets (cutting tools, fixtures, files) and interfaces for tasking and referencing external systems, plus companion relationships with OPC UA: the two communities maintain a companion specification mapping MTConnect's model into OPC UA for plants standardizing on UA servers.

Where it fits

MTConnect owns machine monitoring: OEE, utilization, downtime classification, and condition signals for machining. It is deliberately read-only — no program upload, no overrides — which simplifies security reviews and keeps the safety case untouched. Feed agents into a UNS via MQTT connectors, into MES for production context, or into analytics for tool-wear and chatter detection.

Deployment advice: prefer controller-native or vendor-blessed adapters over screen-scraping; keep agent polling cycles aligned with the controller's update rate (faster polling buys nothing but load); version-pin your data dictionary per machine model; and record the machine's clock source — timestamp quality decides whether your spindle-load correlations are science or astrology.

References

• MTConnect: shop-floor equipment connectivity standard
• Modern Machine Shop — machining technology coverage
• OPC UA companion specifications: a guided tour — Shopfloor