As digital industrial networks weave their way through applications it's hard for those applying the technologies to think about working without them. For operators, however, networks are best appreciated when they go unnoticed…in the oil field (Control Engineering, July 1998, p. 114), on the city bus, and in manufacturing and processing.

Digital industrial networks are expanding into other applications. For example, the WorldFIP (Nancy, France) network reached down into device-level networks earlier this year. Initial sales of the Device WorldFIP Development Kit were reported strong by the organization.

Echelon (Santa Clara, Calif.) and Cisco Systems (San Jose, Calif.) agreed in June to jointly develop technology to link Echelon control networks with Internet Protocol (IP)-based data networks to escape "expensive leased line phone networks and increase network management visibility into critical business process control systems." C3 Communications—an Austin, Texas-based subsidiary of Central & Southwest electric utility—is using LonWorks networks and Cisco products in metering automation and telecommunications services.

CANopen fieldbus has jumped on the "bus."

Bus manufacturer Neoplan (Stuttgart, Germany) has developed a hybrid bus for public transportation. CANopen communicates to two servo controllers to drive the wheels, one servo controller for steering, and one frequency controller for the battery.

Additional Profibus, CANopen, ControlNet, Fieldbus Foundation, and Interbus application notes follow. For more about "Networked I/O Stategies…" see the adjacent Year of the Network article.

Only a few of the dozens of networks are mentioned here, but we're interested in hearing about others, especially use of Ethernet for manufacturing and process control. E-mail ideas to mhoske@cahners.com.

For more information, visit www.controleng.com/info:

The Bochum, Germany, production line of Adam Opel AG turns out 1,200 Opel Astra cars daily. Investments of hundreds of millions of German marks have resulted in improvements in environmental production, workplace ergonomics, and productivity.

In 1994 Opel decided to standardize on Profibus open communications at the field level in all European plants for bodyshell production. Now Profibus is being used successfully in most areas, including the press shop through bodyshell production, paint shop, and final assembly. Cost savings and flexiblity using Profibus in Bochum means the digital industrial network will now be installed in other factories of the European Opel/Vauxhall conglomerate.

Press shop, bodyshell

The Bochum site uses over 22,000 tons of steel per month; Opel is Germany's second largest steel consumer. Modern information technology controls supply of steel sheets to Astra production lines. Computers continuously monitor material consumption and coordinate the just-in-time supplies online.

Applying up to 3,200 tons of pressure each, the two modern transfer press lines at Opel's production plant shape as many as 900 fenders, doors, engine hoods, and side panels for Astra models per hour. Sheet steel components for all five European Astra production lines are produced in Bochum; press lines work nearly round-the-clock. Changing dies weighing several tons, which can take several hours in conventional plants, can be done automatically within minutes, using a system of more than 100 electric motors, hydraulic valves, and actuators. Motors and valves from varied manufacturers connect to the central PLC controller through Profibus. Two wires transfer data, parameters, and control commands. Profibus reduces downtime and increases flexibility.

Opel engineers have also installed high-tech systems in the body shop, including approximately 190 computer-controlled robots that do 98% of welding operations. Bochum also claims to be the first automotive plant to use advanced laser technology in volume production scale. A high-energy light beam joins the frame to the outer shell of the Astra engine hood, improving quality. In the fully automated body assembly, robots spot weld 2,000 points.

The robots can rapidly switch among sheet-metal components for the three and five-door Astra hatchback variants, the Caravan, and Cabrio convertible. Hundreds of automated electrical welds take place per minute. Accordingly, the fast control components for short cycle times also must be immune to high electromagnetic interference.

Opel uses multiprocessor PLCs from Bosch and welding robots from GE Fanuc together with a wide spectrum of peripheral components such as Siemens I/O devices, Festo valve blocks, and SWAC operating panels, which all communicate with the PLC through Profibus-DP. Profibus-DP operates here at 12 Mbit/sec, allowing bus cycle times of less than 1 msec.

Profibus-FMS is used for communication between the PLCs at the cell level. And Profibus-DP connects decentral peripherals such as I/O devices, motor drives, valves, and operating panels to the PLC at the field level. Computer integrated manufacturing (CIM) based on open communication systems has proved itself many times in online operation.

Water-based paint shop

After robots and welding machines have assembled the sheet steel components for the Astra bodyshell, vehicles journey 5.5 km through the modern paint shop. Bochum uses water-based paints, rather than conventional organic solvents. Application of the various paint layers takes place largely automatically.

When the door, cockpit, and engine modules are finished, a conveyor system delivers them directly to the final assembly line. The material feed systems are all controlled fully automatic using PLCs from Schneider Automation and Siemens. All peripherals such as I/O devices, motor drives, and operating panels are installed directly adjacent to the assembly line and connected to the PLCs with Profibus-DP. Control cabinets often only contain the PLCs themselves.

The network contains several kilometers of cable; about 300 Profibus-DP devices from a range of manufacturers are used in the final assembly area. To cope with the large distances, fiber-optic cable is also used for Profibus networks at some places. Decentralization has reduced cabling costs considerably. Use of Profibus facilitated recent modernization of the final assembly area in six weeks.

Dipl.-Ing. Michael Volz is operations manager for Profibus International

Avenor (Gatineau, Quebec, Canada) recently completed startup of a FOUNDATION fieldbus installation using the new Fisher-Rosemount (Austin, Tex.) Fieldbus PlantWeb Builder suite of products.

Avenor's installation is the first use of device-based PID control in the pulp and paper industry. Four PID control loops, using common function block programming techniques, are distributed amongst transmitters, control valves, and the DeltaV control system. Pulper level control resides in the level transmitter; pulper consistency and storage consistency controls reside in the control system; and storage pressure control resides in the digital control valve actuator/controller.

"Even though we are using a mix of conventional and fieldbus devices, the function block configuration features of DeltaV provide a consistent look-and-feel, regardless of the I/O type or the final destination of the control strategy," explains David St-Onge, Avenor's corporate manager of technology development for process automation.

Avenor's kraft pulper installation combines a mixture of FOUNDATION fieldbus certified and conventional products connected to a Fisher-Rosemount Systems DeltaV controller.

Certified fieldbus I/O devices include three Rosemount transmitters for level, one for pressure, and one for temperature; and five Fisher Controls FieldVue digital valve controllers mounted on a variety of manufacturers' control valves.

Conventional I/O devices include:

• Pulp consistency transmitters (2);
• Magnetic flowmeter (1);
• Discrete inputs(15); and,
• Discrete outputs (20).

"We made a strategic decision to implement FOUNDATION fieldbus because we believe the technology is promising and we wanted to learn how to put it to work for us," says mill manager Patrice Cayoutte.

"Level, temperature, and pressure transmitters were commissioned with the device-based control, and were communicating to the control system in a matter of minutes," reports Avenor process automation engineer Trung Phung, resulting in 90% less commissioning time.

Fisher-Rosemount's Performance Solutions group provided project design and engineering. Avenor and local Fisher-Rosemount representative Laurentide Controls shared site services for configuration, installation, and commissioning.

"We did a substantial portion of the work in-house to gain a better understanding of FOUNDATION fieldbus technology and how to use it in future applications," says Mr. St-Onge.

"We see fieldbus technologies potentially eliminating unscheduled downtime by using advanced features such as valve diagnostics," adds Mr. Cayoutte.

David Harrold, senior editorFieldbus Foundation