PC-based automation paves way for integrated factory

Staff -- Control Engineering, 4/1/2004

After more than 20 years with Grand River Rubber & Plastics, vice president Joe Misinec was growing increasingly concerned about his company's primary automation products supplier. What troubled Misinec was that the supplier was changing hardware platforms again—twice in a short time period. In addition, this change would leave Grand River with little operational flexibility. It would also make it difficult to integrate components within the company's machines, which were used to produce its specialties: lathe-cut washers and tubular gaskets. A further complication for Misinec was that new equipment, software, and training required by the change would cut into Grand River's profits. This was not the direction Misinec wanted to take the 200 employees of the Ashtabula, OH-based plant and its $30 million in annual sales revenues.

What Misinec needed was an integrated system that would increase production efficiency and reduce scrap.

"From a technical standpoint, it's very difficult to integrate different supplier's products and architectures," Misinec says. "We were using different companies for PLCs, motor drives, HMIs, counters and timers—and then you have to integrate the mechanical parts. If the tolerances are not just right, it is difficult to fit them together. It was the same thing with the automation and control system."

Moving away from the original supplier, which had worked with Grand River since 1987, was a difficult step but one Misinec knew had to be made. So he immediately began replacing the company's automation and control system, including PLCs and HMI devices, with Siemens' PC-based automation solution.

The company's gasket-making process begins with the receipt of 24 x 36-in. sheets of 1/2-in. thick rubber made by a custom mixer. The sheet is extruded in a tubular shape in various inside and outside diameters (IDs and ODs). In a curing operation, the rubber is processed and given "memory." Then, it is ground to an exact OD specification. In the final stage, lathes cut the rubber into gaskets and a slitter indexes them from one end of the tube to the other. Finished gaskets are boxed and shipped to customers in a number of markets, including the container, water heater and quick-disconnect-coupling industries.

The Siemens' approach replaced a hardware platform with a software-based one. Each of 27 lathe-cutting machines was equipped with a Simatic WinAC controller for PC-based automation. WinAC controller uses a CP5613 PCI card to communicate over a Profibus network at 1.5 Mbaud with ET-200M I/O and Siemens Micromaster drives installed on each machine. Each machine is also equipped with a Simatic TP170B touch panel.

"It took a year and a half for the project from beginning to end because of the number of machines involved," says Misinec. "We were not able to take them all at once and retrofit them, so we did one at a time."

Although the driving force behind the retrofit was to reduce scrap, Misinec also wanted to move away from a hardware-based platform. "A hardware platform has a fixed scan time and you can't change it," Misinec said. "The PC operation can be changed by how much you allocate to the memory versus the machine process. All of a sudden we jumped from 80 pieces of product per minute to 140 by being able to adjust the scan time."

Today, thanks to the shift, Grand River Rubber & Plastics has reduced raw material consumption 5%.

"We've paid back our investment in the new automation system in two years," Misinec said. "We brought one machine on line per month, so the investment was recouped as soon as the machines were up and running. That just shows how much you can save by lowering scan times from 40 ms down to just 1 ms."

Reducing the time needed to set up the lathe-cutting machines was also critical to the success of the retrofit. Cutting the gaskets to proper specifications is one of four critical functions of the process. Any delay or downtime in one area affects the other three and brings production to a halt.

"We saved about 20% in time to retrofit each machine compared to conventional hardwiring," Misinec said. "Profibus figured in heavily here, reducing large amounts of wiring with a cable."

Machine downtime has also been drastically reduced. The machines used to require four maintenance hours per shift. Now maintenance is seldom called. "We are also spending 50% less in inspection costs," Misinec says.

Because of the success of this initial deployment, Grand River Rubber & Plastics is taking Siemens' Totally Integrated Automation platform plant wide. Misinec says the company is currently installing Siemens products on a new generation of bayonet machines, grinders and cut-to-length units. In addition, the company is incorporating Simotion machine-control technology on its lathe-cutting machines, striving to further reduce set-up time and scrap. Simotion incorporates motion control, logic and other technology functions, including temperature and pneumatic control, into a single, integrated system.

A few of Misinec's associates questioned the cost effectiveness of discarding new equipment as part of a retrofit. However, after each machine was completed, their concerns were met with beneficial results.

"We have achieved overwhelming success by going from a PLC to a PC-based solution," Misinec says. "Because we switched from a hardware platform to a software platform, we've reduced scrap by 5% and have spent 50% less on secondary operators. That all goes to the bottom line."