An Ethernet-based field network solution for Honda

28 September 2015

An increase in efficiency of production and operation management has been achieved by Honda Motor Company at its Yorii plant in Japan since the introduction of an Ethernet-based CC-Link IE Field Network.

The CC-Link IE solution allows for communication within a unified network for control signals from factory automation devices such as PLCs, production management information, and safety signals. The success of this project is now leading to the expansion of the industrial communication solution into other Honda overseas factories, including a new plant in Mexico.

The Yorii plant was built with a view to increasing cost-competitiveness through the implementation of efficient production and energy management. The plant fulfills the role of ‘mother factory’, sharing its production technology and know-how throughout the global Honda enterprise.

As the construction of the Yorii Plant proceeded with this mission in mind, it was late 2011 when the design and selection of production line control devices began seriously. 

Selecting control devices
Taku Yokomukai, maintenance supervisor for vehicle body assembly production line facilities at the plant, was involved with the selection of control devices. He said: “We talked a lot about what kind of control devices and networks would be appropriate for a state-of-the-art factory.” The first issue that arose when constructing a control network for the vehicle body assembly line was how to handle the overall network architecture. “We did consider a flat construction linking the whole plant in a single network, but given the possibility that a single failure could stop the entire plant’s network, we decided we were better off with multiple networks.” 

However, constructing individual networks by application would result in a more complex system as well as increasing introduction and operation costs. While considering the system architecture, the team also identified two functions essential for the network. One was the centralised ‘visualisation’ of factory automation control devices. The vehicle body assembly line alone uses many PLCs, making individual management inefficient. The target was an environment in which factory automation control device setup, monitoring, and failure detection could be centralised through the network.

The other essential function was the communication of safety signals through the use of interlocks, to detect when a worker enters a prohibited area or approaches a robot. The traditional practice of using relays to configure a hardware-based safety circuit presented the issue of serious time loss during line expansions and changes. A decision was made, therefore, to incorporate safety signals into the network as well, aiming for a structure that would allow flexible line changes.

Yokomukai focused on Mitsubishi Electric's CC-Link IE Field Network solution whereby a single Ethernet cable allows communication of control information for PLCs and controllers as well as maintenance and safety information from the connected devices.

"When Mitsubishi Electric introduced the CC-Link IE Field Network to us, I discovered that it could handle maintenance and safety information as well, reflecting our various on-site needs. I felt that it would allow us to build a simple and high-reliability network suitable for the plant," said Yokomukai.

Compatibility with the control devices was also an important point. “To fulfill the projected production numbers, the vehicle body assembly line was going to have to be maintained at a near constant 100% operating rate, requiring reliability and guaranteed performance from the control devices. Our in-house proposal was for control devices from Mitsubishi Electric. Because the CC-Link IE Field Network is compatible with Mitsubishi Electric control devices, we felt that we could construct an optimal system by combining the two,” continued Yokomukai.

The CC-Link IE Field Network is an Ethernet-based field network following the physical and data layers as defined by IEEE 802.3. As well as covering high-speed I/O and control of distributed controllers it offers flexible network topology options such as star and ring types, allowing freedom in the arrangement and configuration of connected devices. In addition, it supports management and maintenance of controller devices and features a safety communication function that allows for the sharing of safety information among multiple safety PLCs.

The Honda Yorii plant began operation in July 2013, and moved to full operation with the introduction of a second shift in September 2013. Yokomukai “We really get a sense of the effect of the visualization that we were aiming for originally, even the way that when there’s trouble with the equipment or control devices, the diagnostic functions of CC-Link IE Field help us locate the problem faster,” concluded Yokomakai. “The vehicle body assembly line uses as many as 50 PLCs. We are able to get a centralised overview of the line status, making operation management efficiency much higher. The recovery time has also been shortened.” 

Line expansion and adding new safety functions is a simple matter of connecting a LAN cable to a vacant port on the CC-Link IE Field Network. An interlock can be added immediately in Mitsubishi Electric’s Safety PLC, reducing the workload considerably.

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