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1 July 2006

Auto assembler lines up with Ethernet

Lear Corp., a manufacturer of aircraft assemblies, also serves the automotive industry and supplies parts for the seat, instrument panel and cockpit, door, and overhead and flooring systems. Visteon Corp. is an automotive supplier with corporate offices in Van Buren Township, Michigan, China, and Germany. Its 170 plus facilities in 24 countries specialize in designing, engineering and manufacturing climate, interior, electronic, and lighting components for Ford, Chrysler, and other automakers. 

These components include instrument and door panels in varying configurations, depending upon vehicles’ make, model, color, and included options. Vehicles coming down an automotive assembly line need different panels because of their varying types of HVAC systems, sound and speaker systems, wiring harnesses, and other components. So selecting the right parts for installation becomes key as cars move down the assembly line. It is also important to verify chosen parts for quality assurance, regulatory compliance, and liability purposes.

Manufacturers at plants in Michigan and across the Midwest use discrete manufacturing processes with Ethernet I/O systems. “Typically, an auto assembly line will have perhaps 10 or 20 different workstations,” said Greg Deel, a project manager at Pyramid Solutions, a Michigan-based software, engineering, and systems integrator. “Running individual serial lines to each one works well enough but isn’t very practical.”

Nevertheless, the automaker installed this exact architecture and ran it in some of its plants. Each workstation (nearly 17 totaled) harbored a dedicated PC enclosed in a protective cabinet and connected to an Ethernet brain board through the serial port on the back of the CPU. This 1-for-1 setup performed effectively but was problematic in terms of its excessive wiring and hardware, and the fact that 17 individual setups on the line increased the likelihood of something going wrong. 

The automaker fixed the problem by having its architecture upgraded with blade PCs residing in a single cabinet in the center of the line. The Ethernet systems are now distributed around the line and connected to a network switch (instead of the individual PCs). Each one is now capable of handling connections for multiple workstations. 

“Switching to Ethernet helped consolidate things considerably,” Deel said. “With everything connected via Ethernet, we were able to put the I/O in a more out-of-the-way place and get rid of those bulky cabinets. Each Ethernet unit can handle up to 16 four-channel modules. That’s 64 I/O connections—enough to handle the equipment at five or six workstations.”

The Visteon and Lear plants also installed Ethernet I/O systems at various points on the line to control and monitor the conveying systems that move the automobile shells from one workstation to the next. The system connects to several different devices, such as conveyor quadrature encoders, electronic devices used to convert the position of a shaft or axle to a digital code, thereby making it possible to detect the direction and calculate the speed of the conveyor’s movement. The quadrature encoders connect to the system via digital input modules. The processor or brain captures the operational data, thereby making access easy for any PC or operator interface terminal connected to the Ethernet network.

The systems perform control functions for assembly-line, pick-and-place systems, which use industrial robotics to sequentially choose and assemble appropriate auto parts from a diverse selection. The Ethernet unit uses digital output modules to turn on lights that identify correct parts for the system’s picker.

The Ethernet system plays a key role in verification and quality control at Lear, which manufactures systems for the Plymouth Neon and Dodge Durango, among others. The systems configuration enables it to control call boxes that assembly line operators use to activate alerts in the event of critical or emergency conditions. One such condition could be a need to stop the assembly line altogether, but more typically, they use the call boxes to notify specific plant floor personnel (production manager or quality assurance supervisor) when a matter requires their immediate attention. If no one notices the visual indication from the bulb or LED on the call box, the Ethernet system provides an interface from the call boxes to additional lights, horns, and marquees throughout the plant. Operators manually activate the call box at their workstation if they are running low on parts. The callbox then sends a signal to the system, which, in turn, activates a siren intended to alert the materials manager.

The Visteon and Lear facilities deployed their systems without replacing, modifying, or otherwise disturbing the existing installed control systems. And while prospective users are reluctant to retire automation and control high performing hardware, what they might really want is supplementary functionality, such as “added control function at one or two workstations or quick data acquisition from one part of the manufacturing process,” said Jason Linton, Lear plant manager at the Warren facility with the Ford F-150 cockpit assembly. In fact, the installed hardware’s openness allows the manufacturer to integrate it into installed control systems and configure it to perform its function “without disturbing I/O or field wiring and little or no software reprogramming.”