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EtherNet/IP: A Fieldbus First, Network Second

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Wanting to replace multiple fieldbuses with a single control network standard, a Tier One automotive manufacturer chose EtherNet/IP.

With 35 manufacturing and engineering locations spread across 13 countries, American Axle & Manufacturing, Inc. (AAM) recognized that reducing the network complexity of its manufacturing operations. AAM, headquartered in Detroit, Michigan, is a global Tier-One automotive supplier of driveline and drivetrain systems and related components.

By the mid 2000s, AAM’s manufacturing lines were operating using up to five different fieldbuses. The complexity resulted in lengthy time-to-deployment of new assembly lines, multiple sets of training documentation, and costly downtime for maintenance. In 2006 Jeff Smith, technical engineering lead at the company’s world headquarters in Detroit, Mich., was charged with identifying a single fieldbus that could operate across all systems.

Smith is a strong advocate for standards as a way of optimizing investment and performance. He realized that future growth and operations efficiency was dependent on finding a global solution that would reduce deployment, training and maintenance costs, and also support a proprietary supervisory system AAM was developing.

“Prior to 2006, there really weren’t any fieldbus standards,” said Smith. “We chose EtherNet/IP because it was ready to allow us to achieve our goals.” For AAM, EtherNet/IP—a standard managed and promoted by ODVA (www.odva.org)—is a fieldbus first and a network second, he said. 

“If EtherNet/IP weren’t capable of controls functions such as reading inputs and writing outputs, we would have continued looking,” Smith said. “The ability to add security and infrastructure connectivity, while important, was not our primary goal; our goal was to replace multiple fieldbuses with a single solution. 

“I credit our ability to deploy quickly and our long-term success in this project to focusing on our objective, rather than starting with the network and figuring out how it could address fieldbus issues second,” he adds.

As related by Douglas Stubbs, applications engineering manager for industrial networking vendor Belden Inc. (www.belden.com), AAM approached finding an Ethernet infrastructure vendor in an organized and effective manner. Engineers wanted a single vendor for networking equipment with global reach, a broad line of reliable, industrially hardened products, and what Smith calls “justifiable pricing.” The objective: to simplify ordering, deployment and maintenance.

Standardizing on EtherNet/IP required coordination with AAM production line equipment suppliers. The company informed suppliers that they would need to offer EtherNet/IP compatibility within a defined timeline, and assisted a number of its suppliers with that development to help them achieve the goal on time. 

Smith’s team, with the assistance of distributor McNaughton-McKay and automation vendor Rockwell Automation (www.rockwellautomation.com), created a simulated manufacturing environment with a rigorous set of test cases. AAM also developed a turnkey industrial Ethernet network based on Belden’s Hirschmann brand of network switches. Products included OpenRail Series RS20 managed switches for station panels and Mach 100 hardened rack-mount switches in network SCADA panels, plus Belden’s Bonded-Pair technology patch cords.

The AAM strategy to develop a configuration that could be deployed at all plants globally was a success. Key outcomes of the standardization program are:

• “Cookie-cutter” network configurations reduce configuration, training and maintenance costs.

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• Downtime events due to network related issues are now rare, and less downtime saves money and improves product delivery. 

• Changeover flexibility. When AAM decided to move its assembly systems’ EtherNet/IP networks from star to ring topologies, they found the transition to be smooth.

Prior to standardization on EtherNet/IP, it took four to six months and significant onsite engineering support (often multiple engineers) to launch a new assembly system. In 2007, shortly after the Ethernet standard was defined, AAM flawlessly launched four assembly lines simultaneously in four months, with no headquarters engineering support required.

COMPANIES IN THIS ARTICLE: Belden Inc., Ethernet/IP, Rockwell Automation
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Comments

One have to be specific when saying Ethernet is replacing fieldbus because there are two distinct and very different levels of fieldbus: H1 fieldbus and H2 fieldbus. H2 fieldbus is used between the control system and underlying package unit PLC, remote-I/O, drives, motor starters, MCC, and wireless gateways at level 1-1/2 of the Purdue reference model (and ISA95) and includes protocols like Modbus/RTU, PROFIBUS-DP, and DeviceNet etc. and without a doubt their Ethernet counterparts Modbus/TCP, PROFINET, and EtherNet/IP are gaining in popularity. On the other hand, H1 fieldbus is very different. H1 fieldbus is used for sensors and actuators at level 1 of the Purdue model, where the dominant connection technology is hardwired analog 4-20 mA and discrete on/off signals. I interpret the article as if sensors/transmitters and positioners/actuators/valves at level 1 of the Purdue reference model (ISA95) use analog 4-20 mA and on/off signals hardwired to an I/O subsystem at level 1-1/2 of the Purdue model that connects to the controller using Ethernet, where Ethernet now takes the place of multiple traditional “H2 fieldbus” like Modbus/RTU, PROFIBUS-DP, and DeviceNet etc. But why start and end the digital networking at this level? In my personal opinion, digital communication should be used all the way down to the thousands of sensors/transmitters and positioners/actuators/valves at level 1 of the Purdue model. At level 1 of the Purdue model I do not see Ethernet down to proximity switches and solenoids etc. Instead, at this lower level, fully digital plants use one of the “H1” level fieldbus protocols to provide digital communication all the way including the “first meter”. For factory Automation the H1 fieldbus protocols connecting sensors and actuators are ASI, IO-Link, and CompoNet. In process control the H1 fieldbus protocols connecting transmitters and valve positioners are: FOUNDATION fieldbus and PROFIBUS-PA. The H1 fieldbus and Ethernet complement each other to eliminate hardwired 4-20 mA and on/off signals. Fieldbus enables more sensors and more data which in turn drives the need for Ethernet at the higher levels. One size does not fit all, this is why the “CIP suite” includes EtherNet/IP, DeviceNet, and CompoNet, and the “PI suite” includes PROFINET, PROFIBUS-DP, and PROFIBUS-PA, and the “FF suite” includes H1 and HSE.

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