Smart Manufacturing needs consistent, standard mechanisms for accessing devices, describing data and its meta-data characteristics, and moving that data securely and reliably.

The CESMII Building Blocks for Smart Manufacturing

Figure 1 – The CESMII Building Blocks for Smart Manufacturing
(Used with Permission)

If one thing is clear going into 2022 and beyond, manufacturers must adopt “Smart Manufacturing” tools and techniques to be globally competitive in the future. Unfortunately, Smart Manufacturing (SM) can represent many different things. It can mean analytics, predictive maintenance, autonomous process control or just standardized data collection.

One of the leading organizations working to clarify Smart Manufacturing, promote it, educate and unite the manufacturing community and develop the enabling technologies is CESMII1 ( CESMII views Smart Manufacturing as the ability to collect data, contextualize, process and model it to make more intelligent decisions about a manufacturing process. This kind of system offers significant advantages to manufacturers:

  • Faster, open and reliable communication between devices, people and partners from an open and interoperable ecosystem.
  • Optimization of process and material flows.
  • Faster, more informed decision making.
  • More rapid product changes with minimal intervention and easy reconfiguration.
  • Proactive and semi-autonomous processes that act on near real time information.

Data Collection Is The Key To Smart Manufacturing

Unfortunately, data collection, which is the key to a Smart Manufacturing system, is where manufacturers are bleeding time and money. Choosing the right software interfaces and data models to cohesively move data into Industry 4.0 and Smart Manufacturing applications isn’t easy. Many groups and trade organizations are creating standards and writing data models for all sorts of applications and industries. CESMII, Namur2, the OPC Foundation and many other organizations are proposing standards. Some are actual standards; others are just documents. Manufacturers are faced with the question of waiting or moving forward with something that might not be supported later.

This lack of standard is, as usual, going to cost manufacturers money. Manufacturers face a complex jigsaw puzzle of software standards used by devices and applications that are largely incompatible and difficult to cohesively assemble. Some software systems provide Application Programming Interfaces (APIs), some custom and some not. Many application developers love Web Services, especially HTTP with a RESTful interface. And, of course, there are those out there who will only give up their obsolete OPC drivers when it’s pulled from their cold, dead hands.

This mish-mash of interfaces means that even though everything is largely on Ethernet, nothing meshes together easily. What often happens is that people who need the data create secondary, parallel applications and systems – often undocumented and unsupported – to work around what’s in place. More time lost, more information lost, costs rising – it’s a nightmare.

One of the big battles is over MQTT and OPC UA. The sides have hardened. Both have adherents that remind one of religious crusaders. Both denigrate the other and claim that all the “big vendors” and cloud companies are moving in their direction. Both say they have the simpler, easier, more integrated solution. Those of us with more gray in our hair and a more leisurely gait have seen this before, not only in the pre-Ethernet days but with Profinet IO vs EtherNet/IP, and PCs vs PLCs.

Seven Things to Know About Smart Manufacturing Data Collection with OPC UA and MQTT

  1. Data Collection – Devices (see below) and tools are available to move data from closed factory floor systems to both OPC UA and MQTT. The ability to interface with proprietary and semi-proprietary factory floor systems and collect data is not an issue with either technology.
  2. Information modeling – Information Modeling in OPC UA is vastly superior to MQTT. The OPC Foundation is working closely with all the industry trade groups to define specific Information Models for various industries. Only some of these are being put into practice.
  3. Applications – Applications that simply move data from one place to another are perfect for MQTT. OPC UA is more appropriate for applications where modeling factory floor data adds usability to the application.
  4. Security – OPC UA implements a more sophisticated and flexible security model that provides layers of security that include authorization, authentication, and auditing. The security level can be chosen at runtime and tailored to the needs of the application or plant environment. MQTT simply uses HTTPS.
  5. Communications Architecture – Both technologies use a publish/subscribe architecture that minimizes bandwidth consumption and leads to more efficient communications.
  6. Flexibility – MQTT is unquestionably the more flexible of the two technologies but that is only because it carries raw data in most applications. OPC UA offers different kinds of flexibility: the ability to discover nodes, interrogate data models and contextualize data values using data relationships and meta-data.
  7. Future Proof – OPC UA is designed in a way that is compatible with a future where every device is described by a Cloud-based data model. MQTT has yet to develop this capability.

Overview of Data Collection Processes of OPC UA and MQTT

OPC UA Data Collection

Sample Information Model for a Curing Oven

Figure 2 – Sample Information Model for a Curing Oven

OPC UA is the successor to OPC (Open Process Control). It provides more open transports, better security, and a more complete information model than the original OPC. OPC UA provides a very flexible and adaptable mechanism for moving data between the kinds of controls, monitoring devices and sensors that interact with real-world data and enterprise-type systems.

OPC UA is an open architecture, standard way for applications, controllers, sensors and other devices to interact. OPC UA uses scalable platforms, multiple security models, multiple transport layers and a sophisticated information model to allow the smallest dedicated controller to freely interact with complex, high-end server applications.

The Information Model is the heart of OPC UA. An Information Model (Figure 2)is nothing more than a logical representation applied to a physical process. An OPC UA Information Model can represent something as tiny as a screw, a component of a process like a pump, or something as complex and large as an entire filling machine. The Information Model is simply a structure that defines the component, devoid of any information on how process variables or meta-data within that structure are accessed.

MQTT Data Collection

MQTT is a fundamentally different kind of architecture from what we’ve ever used on the factory floor. The publish/subscribe architecture is unique. There have been other publish/subscribe architectures proposed and implemented, but MQTT is the first widespread technology using that architecture to achieve common acceptance on the factory floor.

The publish/subscribe architecture allows a message to be published once and with any number of clients that have complete message decoupling between the producer of the data/events and the consumer(s) of those messages and events. Data is arranged by topic in a hierarchy with as many levels of subtopics as needed. Clients can subscribe to a topic or a subtopic.

The other big difference between MQTT and industrial protocols is that it utilizes a central server, known as a broker, to facilitate communications between devices. A broker receives the information from the servers and matches the information to consumers by topic subscriptions. The information is distributed to every consumer that matches the topic. If no consumer requires the information, the information is discarded.

How to connect the Factory Floor with OPC UA & MQTT

Real Time Automation is uniquely positioned to support manufacturers in this environment. Our communication gateways support both OPC UA and MQTT technologies. That means that control engineers and operations staff now have the ability to reach into a Siemens S7, an Allen-Bradley Logix controller, an Allen-Bradley PLC5 and other controllers and devices to extract information and publish it to an MQTT broker or present it as an OPC UA Server.

Like all RTA gateways, the unit is extremely configurable. You can pick single tags, User-Defined Tags (AB), Data Space Blocks (Siemens) and other data using any one of the many protocol drivers in the RTA protocol suite. And on the MQTT side, the gateway publishes that data using topics that you define to the brokers you identify.

Our soon to be released factory floor data collection software platform will also support both MQTT and OPC UA and collect data from many different factory floor technologies, manipulate it, scale it, normalize it and send it out over OPC UA and MQTT..

1CESMII is the Smart Manufacturing Institute. It is a USA government funded, non-profit organization tasked with driving Smart Manufacturing. Find more at
2NAMUR is an international user association of automation technology and digitalization in process industries.

A Perfect solution…?

There is no perfect or right solution! Like many other technology decisions in automation over the last 20 or 30 years, there is not and will not be, a clear winner. Both technologies will grow and prosper.

OPC UA will be a good solution for many in Smart Manufacturing who anticipate a future where data modeling is key to productivity and competitiveness. OPC UA is the only solution that promises support for all of the data model architectures being developed for Smart Manufacturing systems of the future.

But MQTT can also be a good choice as well for many small, non-closed loop IoT applications. It has a large number of adherents because of its small footprint, simplicity and “push” architecture. It is a reasonable solution for IoT prototyping, small, in-house applications and other applications not requiring widely adopted data models. It may not be the right solution for the coming era of open, widely available data models for all automation devices.

Developers, integrators and system architects will eventually come to learn where they have the best success with OPC UA and the best success with MQTT. Manufacturers are going to have to understand, support and work with both technologies and figure out which works best in which applications.

For detailed information on moving data from a PLC or other network to a broker over MQTT, contact us:

John Rinaldi
Chief Strategist and Director of WOW!


John Rinaldi is Chief Strategist and Director of WOW! for Real Time Automation (RTA) in Pewaukee WI. With a focus on simplicity, support, expert consulting and tailoring for specific customer applications, RTA is meeting customer needs in applications worldwide. John is not only a recognized expert in industrial networks and an automation strategist but a speaker, blogger, the author of more than 100 articles on industrial networking, and six books including:

For more information on OPC UA, a good place to begin is the book, OPC UA – The Everyman’s Guide to OPC UA. You can get it at no charge by visiting Just use “112” as the publication code.