PARK RIDGE, Ill. — General Motors Corp.'s decision to use Ethernet on the floor of a new automotive engine plant opening next month (July) in Tonawanda, N.Y., points to the incremental progress of Ethernet in factory automation, but also to its shortcomings.

The GM plant will be using FL-net, an Ethernet-based protocol that is more deterministic than Ethernet itself, and which has seen scant deployment in the United States.

FL-net has broad corporate support in Asia, and GM said it has selected the protocol as a matter of convenience—the Asian machine tools it purchased for the Tonawanda plant already incorporated FL-net. GM will use it to link several hundred computer numerical control systems on the floor of the plant.

FL-net is a network that essentially serves as a link between factory floor controllers and front office databases, using standard Ethernet cards and cables. "FL-net is easy for us because it's so much like Ethernet," said Mike White, an electrical engineer at the Tonawanda plant. "We can use Ethernet hubs and Ethernet cables. Like Ethernet, it's fast, and all the components are inexpensive and off-the-shelf."

Although GM's use of FL-net is isolated, industrial automation analysts said the installation is significant because it shows a major manufacturer willing to bring Ethernet to factory floor devices.

"Everyone in the manufacturing community is asking, 'How do I get my Ethernet to talk to my device networks on the factory floor?'" said Tom Bullock, president of Industrial Controls Consulting (Fond du Lac, Wis.). "They know that the leading edge technologies are the ones that will allow host computers in a facility to communicate with devices and machines on the factory floor, as well as customers and suppliers on the outside."

Up to now, manufacturers that wanted to link the factory floor to the front office have used a complex three-layer protocol stack to enable plant floor sensors to talk to industrial controllers, which in turn talk to front office computers. Protocols such as FL-net, as well as competitors such as Ethernet/IP and PROFInet, are enabling manufacturers to pare the three-layer stack down to two layers.

Some analysts expect such protocols to play an important role on the factory floor in the near future. A recent study by ARC Advisory Group (Dedham, Mass.) predicted that Ethernet usage in factory applications would increase by 84 percent in the next two to three years. But an ambitious joint venture of GE Fanuc Automation North America and Cisco Systems Inc. that sought to capitalize on Ethernet's adoption in factories has failed to find its footing.

Moreover, manufacturers are diverging on their use of Ethernet-based protocols. U.S.-based plants are predominantly employing Ethernet/IP, while European plants tend to opt for PROFINet, and Asian plants employ FL-net.

GM stressed that its use of FL-net is limited, and that it is also employing other such protocols, particularly Ethernet/IP. Still, GM's use of FL-net is believed to be one of the biggest North American installations of the protocol to date. Analysts said that up to now, FL-net's exposure here has been so limited that many U.S.-based automation engineers haven't even heard of it yet.

FL-net has, however, garnered big-name corporate support in Japan, where a consortium of 26 companies have banded together behind it.

Factory automation engineers said Ethernet-based protocols such as FL-net are needed because Ethernet, by itself, is not deterministic enough to pass messages between manufacturing machines. Such machines, they say, must have networks that are far more reliable than those used in front office applications.

Still, most automation engineers agree that no Ethernet-based factory floor protocol yet appears to be emerging as a worldwide leader. "A lot of people are agreeing that Ethernet needs to happen [on the factory floor]," said Bill Arnold, product marketing manager for networks at Omron Electronics LLC (Schaumburg, Ill.), a supporter of FL-net.. "They're just not agreeing on which protocol should be used."