Ethernet and the Industrial Internet of Things (IIoT) is driving manufacturing convergence with integration between the plant floor and the wider enterprise. Open communications from machine to machine and device to device are becoming commonplace. Now offering Gigabit speeds and deterministic response, it may seem there is nothing that Ethernet can’t do.

Impact of real-world performance

On paper, many Industrial Ethernet versions have the capability to provide a communications backbone in motion control and axis synchronisation applications. However, baseline figures are not always indicative of real-world performance. When considering the wider operating environment however, that doesn’t necessarily make it the only choice in every application.  Combining Ethernet and a dedicated network technology offers the best of both worlds; speed of installation, operational performance and plant-wide connectivity.

Mitsubishi Electric’s Product Manager Barry Weller argues that despite the seemingly ubiquitous Industrial Ethernet offering speeds high enough for even demanding deterministic motion control applications, there is an important role for dedicated motion networks

In a heavy manufacturing application where there are welding robots and high power motors for example, there is a lot of high-speed motion activity, but also a lot of potential electromagnetic interference and electrical noise. Since industrial Ethernet at machine and plant floor level is still frequently run over copper cable, it is susceptible to noise and interference and may not provide the optimal solution, as any resulting loss in data packages, could easily cause a machine interruption or a scrap product.

A USER AND DEVELOPER’S VIEW

As a long-time user and developer of servo systems and products Mitsubishi Electric developed a dedicated motion network technology called Servo System Control Network (SSCNET) to provide synchronous high-speed bidirectional communications between the controller and the servo. SSCNET will control up to 96 axes simultaneously, and the latest MR-J4 servo drive, SSCNET III delivers bus cycle times of just 0.44ms. SSCNET III uses optical fibre cables to significantly improve resistance to noise from the power cables and external devices. Optical fibre also simplifies installation and troubleshooting by reducing cabling.

SSCNET III

Using SSCNET III, installers benefit from plug-and-play configuration and great ease of connectivity, with none of the requirements for additional hardware such as Ethernet gateways or switches that you would have with a completely Ethernet based solution. High reliability is assured and users benefit from faster system integration. During operation, all parameters and operational data are made available directly back at the main controller, thanks to the information provided by the SSCNET bus system. As a dedicated network this makes it an extremely fast, stable and robust solution.

Industrial Ethernet is clearly a vital communications tool when it comes to integration with the higher-level enterprise machine-to-machine, peer-to-peer and even some lower level communications. However, when it comes to connecting machinery over long distances and communicating from the factory floor up to an MES layer for example, then Ethernet is king. In the highest speed motion tasks however, a dedicated motion network technology, such as SSCNET III, is a more effective choice. Marry the two and you have an ideal solution.

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