MTConnect vs OPC UA vs FOCAS: How CNC Machines Share Their Data

MTConnect, OPC UA and FOCAS are the three names you meet as soon as you try to get data out of a CNC machine. Each one lets the control share its state, its program and its counts with software. But they do not come from the same place, and they do not give the same access.

This guide explains what MTConnect is and how it compares with OPC UA and FOCAS. It also covers older machines with no network port, and how to check your own machines before a monitoring project. It goes deeper into the protocol step of our complete guide to connecting CNC machines.

Why the Protocol Matters: MTConnect, OPC UA and FOCAS

A CNC control already knows whether the machine is cutting, which program is running and how many parts are done. The protocol is the language the control uses to share that information with software. If the control and the software speak the same language, the connection is a matter of an address on the network. If not, you need a translator, or a box that reads electrical signals instead.

MTConnect is one of these languages, and the one built specifically for machine tools. The protocol decides three things: which data you can read, how much setup the connection needs, and whether you can mix machine brands in the same view.

What Is MTConnect? The Open Standard Built for Machine Tools

MTConnect is an open, royalty-free standard created in 2008 by AMT (The Association For Manufacturing Technology) with UC Berkeley and Georgia Tech. It is maintained by the MTConnect Institute. Its strength is a shared vocabulary: execution state, program, part count, alarms and spindle data have the same names on every compliant machine.

• Read-only. MTConnect reads data from the machine and never writes to it.
• Agent and adapter. An agent publishes the data over HTTP in XML. When the control does not speak MTConnect natively, an adapter translates its data for the agent.
• Common on machine tools. Mazak was among its early adopters, and Fanuc also sells an MTConnect server option for its controls.

OPC UA: The General Industrial Standard

OPC UA (Open Platform Communications Unified Architecture) comes from the OPC Foundation. It was first released in 2008 and became the IEC 62541 standard in 2011. Unlike MTConnect, it is not limited to machine tools: it connects PLCs, robots, sensors and software across the whole plant.

• Read, write and subscribe. Software can browse the data of the machine, read it, write it and subscribe to changes.
• Security built in. Authentication and encryption are part of the standard.
• A model for machine tools. The OPC 40501 companion specification describes how a machine tool exposes its monitoring and job data, so that machines from different builders look alike.
• Often an option. On Siemens SINUMERIK controls, for example, the OPC UA server is a licensed option.

OPC UA is also the link many plants use between the shop floor and higher-level systems. For that side of the project, see how to integrate shop floor monitoring with your ERP and MES.

FOCAS: Fanuc's Own Interface

FOCAS (FANUC Open CNC API Specifications) is not an open standard. It is the library Fanuc provides to read data from its own CNC controls, and in some cases to write to them. Because Fanuc controls are found on machines from many builders, FOCAS is one of the most common ways to read a CNC machine.

• Fanuc only. FOCAS works with Fanuc controls and nothing else.
• Rich data. Status, running program, positions, feed rate, spindle load, alarms and counters.
• Ethernet or fiber. Most connections run over Ethernet, and some controls use a fiber link called HSSB.
• Check the setup. Depending on the control and its age, the Ethernet function may need to be enabled or ordered as an option.

MTConnect vs OPC UA vs FOCAS: Side by Side

For monitoring, the three are not rivals. Each gives you the machine state, the program and the counts. What matters is which one each of your controls offers, and whether your monitoring system reads all three so that every machine ends up in the same view.

Older CNC Machines: Serial Port or I/O Box

Many shops run machines that are fifteen or twenty years old, with no network port or no protocol enabled. They can still be monitored, through one of two routes.

• Serial port. Some older controls have a serial port that can carry information from the CNC program. It gives more than an on or off signal, for example the program running.
• I/O box. When there is no usable port, a small box reads electrical signals from the machine, such as cycle start or spindle on. It tells you whether the machine runs or stops, and nothing about the program.

An I/O box is not a second-class solution for the basics. Status, utilization and stop reasons entered by the operator already show where time is lost. For a low-hardware way to start, see cycle time monitoring with minimal hardware.

What Data You Get Depending on the Connection

Every route gives the running or stopped state, which is the base for automated downtime detection and for the availability factor of overall equipment effectiveness (OEE). Program and part data need a protocol or, on some controls, the serial port. Stop reasons are not in the table because they do not come from the connection: the operator enters them on the screen at the machine, whatever the route.

Worked Example: Three Machines, Three Connections

Here is how a small shop might connect three machines. The machines are an illustration, not a list of tested models.

The three machines appear on the same screen. The older mill shows less detail, but its stops are visible like the others, and that is often where the first gains are.

How to Check Your Machines Before a Monitoring Project

1. List every machine. Note the builder, the control model and the year.
2. Check the network port. Is there an Ethernet port on the control, and is it already used for program transfer?
3. Ask which protocol is enabled. MTConnect, OPC UA or FOCAS, and whether it is a paid option. Your machine builder or distributor can answer.
4. Check the network. The machines need to reach the gateway on the shop network. Bring IT in early.
5. Plan the older machines. Serial port where it works, I/O box where nothing else is possible.
6. Start with a few machines. Connect two or three, check the data against what you see on the floor, then extend.

Where JITbase Fits

JITbase has drivers for MTConnect, OPC UA and Fanuc FOCAS. A gateway installed on your machine network reaches each machine through its IP address and port. The install takes about 30 minutes, as described on the edge platform page. To compare gateway options, see industrial edge gateways for CNC shops.

For older Fanuc and Okuma machines, JITbase reads information from the CNC program through the serial port, with its partner On Time Edge. Other older machines connect through an I/O box that converts electrical signals into MTConnect. That route is limited to machine monitoring: live status, utilization and stop reasons entered by the operator at the machine.

Key Takeaways

• MTConnect is an open, read-only standard built for machine tools.
• OPC UA is a general industrial standard (IEC 62541) that can read, write and subscribe, and is often a licensed option on CNC controls.
• FOCAS is the Fanuc library, for Fanuc controls only.
• Older machines can be monitored through a serial port or an I/O box, with less detail but the same view of stops.
• Choose the protocol each control already offers, and a monitoring system that reads all of them.

Frequently Asked Questions

What is MTConnect?

MTConnect is an open, royalty-free standard for reading data from machine tools. It was created in 2008 by AMT (The Association For Manufacturing Technology) with UC Berkeley and Georgia Tech, and it is maintained by the MTConnect Institute. It defines a common vocabulary, such as execution state, program, part count and alarms, so that software can read any compliant machine the same way.

MTConnect is read-only: it reads data from the machine and never writes to it. An agent publishes the data over HTTP in XML, and when a control does not speak MTConnect natively, an adapter translates its data for the agent.

What is the difference between MTConnect and OPC UA?

MTConnect was built for machine tools, and it only reads data. OPC UA is a general industrial standard from the OPC Foundation, published as IEC 62541, that is used for PLCs, robots, sensors and machine tools alike. It can read, write and subscribe to data, and it has security built in.

For monitoring a CNC machine, both give you the state and the counts you need. OPC UA has a companion specification for machine tools (OPC 40501) to bring the same structure to CNC data. In practice, the right one is the one your control already offers.

What is FOCAS on a Fanuc control?

FOCAS (FANUC Open CNC API Specifications) is the library that Fanuc provides to read data from its CNC controls, and in some cases to write to them. It only works with Fanuc controls. It gives access to the machine status, the running program, positions, spindle load, alarms and counters.

The connection usually runs over Ethernet, and some controls use a fiber link called HSSB. Depending on the control and its age, the Ethernet function may need to be enabled or ordered as an option. Check with your machine builder or Fanuc distributor before a project.

Can an older CNC machine without Ethernet be monitored?

Yes, with two common routes. Some older controls have a serial port that can carry information from the CNC program. When there is no usable port, an I/O box reads electrical signals from the machine, such as cycle start or spindle on.

The serial route gives more information than signals alone. An I/O box tells you whether the machine is running or stopped, which is enough for status, utilization and stop reasons entered by the operator, but not for program details.

Which protocol should a CNC shop choose?

Start from what your controls already offer, not from a preference for one standard. Recent controls often support at least one of MTConnect, OPC UA or FOCAS, sometimes as a paid option. A monitoring system that reads all three lets you mix machine brands without changing the way you work.

List your machines with their control model and year, then check which protocol each one has enabled. Use the protocol where it exists, and an I/O box only for machines that have none.

Does connecting a machine for monitoring change its program?

Monitoring only needs to read data: status, program name, counts, alarms. MTConnect cannot write by design. OPC UA and FOCAS can write, but a monitoring system does not need that permission to show the state of your machines.

Before a project, ask your vendor which data it reads and whether it writes anything to the control. The answer should be clear, and your machine builder can confirm what each setting on the control allows.