Sittin' Pretty

System integrator helps avoid a critical system failure for seat maker.

Staff -- Control Engineering, 12/15/1999

Eleven days...how much time is it really? Eleven days to a child may be an eternity, but tell control systems integrators to completely replace a large control system with a faster, more capable, state-of-the-art control system in 11 days and watch their eyes get as big as saucers.

Johnson Controls (JCI, Mt. Clemens, Mich.), seat manufacturer for DaimlerChrysler's Sterling Heights, Mich., Assembly Plant (SHAP), experienced this situation near Christmas 1998.

The company's just-in-time seat shipping system was becoming increasingly unreliable due to control problems. Traffic from modem data, bar code readers, and controller cards overloaded the PC-based control system, causing data collisions and uncharacteristically long scan times. Users there felt Seriplex version 1 I/O modules needed upgrading.

According to Randy Milikan, JCI's maintenance superintendent, troubleshooting problems was a nightmare. Failure of one field device often took the entire system down. Poor design, little or no alarm annunciation, and lack of system documentation often made locating the guilty field device next to impossible.

Plant personnel at JCI believed a crippling system failure was imminent. JCI had approached control system integrator Patti Engineering (PE, Rochester Hills, Mich.) in July 1997 for system research and consultation.

"The original system was poorly labeled, not well designed, and very difficult to troubleshoot," says Sam Hoff, PE's president, who quickly decided that improving this control system would require replacing it.

For the next year, PE and JCI worked together designing the control solution, which includes an Allen-Bradley PLC 5/80E processor with an Interbus Master module. PE designed a customized graphical user interface (GUI) application in Visual Basic 6.0 for the operator interface. Four Panelview 1000s replaced pushbutton stations and provide local operator interface.

Timing was critical for the project. Over the course of an 11-day Christmas shutdown, the old control system was completely removed to make way for the new control system. Patti Engineering cited meticulous planning and hard work—over the holidays, a team of nine engineers and several electricians put in long hours at JCI.

Interbus functions as the project's distributed control system. "I think there were just certain aspects in the Interbus technology better suited for this application than other solutions," says Dave Foster, PE's engineering vp. One of those aspects is the Interbus Configuration, Monitoring, and Diagnostics (CMD) software. Patti Engineering experienced, first-hand, its usefulness during startup support. On one occasion a photo-eye failed "closed" and shorted out its power supply. CMD showed the last responding node, which narrowed down the location of the problem.

The bottom line is happy customers. Eric Klebba, launch manager for JCI, adds, "I've never heard a bad thing about the system from the people who use it, which pleases me. The new system increased throughput, decreased downtime, and improved troubleshooting."

Comments? Send e-mail to: mdrakulich@cahners.com

For more information from Patti Engineering, visit www.controleng.com/info.