When Ropak Manufacturing (Decatur, AL) bought the rights to make a European StikPak machine and market it in North and South America, one of the first things electrical engineer Richard Matthews did was “Americanize” the controls system. In doing so, he installed a microprocessor-based controller that governed temperature levels in the sealing jaws and sealing rollers. Mounted in the machine’s main electrical cabinet, the controller communicated with the heating elements via a fieldbus, or network inside the machine. Based on operator input entered at the human/machine interface panel, the controller sent output voltage to the heater elements so that they would deliver enough heat to seal the packaging material but not so much heat that the material would be damaged.
However, as the first Ropak-built StikPak machines reached final testing and prototype status, the temperature controller originally selected “didn’t prove as reliable as I’d have liked,” says Matthews. When he heard from a local sales rep about the Tempcon, a new PID temperature controller from Phoenix Contact (Harrisburg, PA), he installed one on a StikPak machine and demonstrated that machine at Pack Expo last November in Chicago. Visitors to the Ropak booth were impressed, says Matthews.
“This temperature controller is much more stable and reliable in the day-to-day on/off signals it needs to send,” he observes. “It’s also easier to program and it occupies about 50 percent less space compared to the temperature controller I was using.”
According to Phoenix Contact, the Tempcon’s ability to maintain tight temperature control is partly a function of programming. “It’s largely our algorithm that makes the difference,” says marketing manager Mike Nager.
On a StikPak machine that produces packages five-up, there is a single pair of sealing jaws for all five lanes and two sealing rollers per lane. That comes to a total of 12 zones where temperature must be controlled. A single Tempcon module can handle eight zones, so the Ropak five-lane machine is equipped with two Tempcon modules.
Sealing temperatures range from about 350°F to 400°F, and the StikPak machine has a rated speed of 100 packs/min per lane, or a total of 500/min. Package contents can be liquid or granular.
Each Tempcon module monitors the temperature signals and controls the heating elements locally and then communicates this information to the HMI via a DeviceNet fieldbus. Because the Tempcon is part of Phoenix Contact’s ‘Inline’ automation system, PID temperature control can be easily integrated into the same fieldbus used to monitor photoeyes, proximity sensors, and actuators. Fieldbus technology provides operators with advanced troubleshooting information and can play a role in faster machine changeover.
