"DeviceNet makes the system incredibly flexible," Rock says. "Adding components only takes a few hours, and the cost per input is less than $50. That's at least 50 percent less than a traditional I/O solution." The network also is a boon to troubleshooting because Lipton can use it to gather diagnostic information and isolate problems. Pinpointing and swapping a faulty device now takes minutes.
Another benefit is that Lipton can manage the system exclusively from the ControlLogix controller. Programmed using RSLogix 5000 software from Rockwell Software, all the logic for the photo eyes and solenoid blocks is stored in the controller. As a result, technicians make adjustments and monitor all network activity from a central platform. They have the ability to restrict access to parts of the system as well. This gives the company an accurate record of what changes are made, by whom and for what reason.
"Basically, the system is self-documenting. ControlLogix makes it easy to keep track of what's happening in the field," Rock says.
In addition, the ControlLogix controller is networked , via an EtherNet/IP connection and Ethernet switch from Nortel , to the 40 Allen-Bradley SLC 5/05 controllers that run the packaging machines. The main purpose of this link is to enable and disable the flow of empty cartons. There are times, for example, when Lipton must take a machine off-line, which means it can't receive cartons. To make sure this occurs (or doesn't, to be precise), the SLC controller for that particular machine communicates its status to the ControlLogix unit.
In addition, the Allen-Bradley PanelView 600 operator terminals tied to each SLC 5/05 now double as an interface to the conveyor system. This helps leverage the investment in PanelView technology already made at each machine.
"Although the Ethernet handshake wasn't essential, it has proven very beneficial," Rock says. "And it's a feature that wouldn't have been possible with many of the other control options we explored."
and reduce downtime
The ControlLogix system has been in place more than six months, and there have been no problems aside from typical start-up bugs. And "no problems" equals "no downtime" -- a dramatic shift from the previous conveyor chassis. "Everyone has confidence that when we encounter difficulties, the system can be repaired and brought back online quickly," Rock adds.
Along with negligible downtime, Lipton saved time and money assembling the system. Compared to traditional hard-wired installations, Lipton saw a 50 percent savings in labor. This ultimately helped the company reduce the cost of commissioning and assembling a control system by one-third.
Given the favorable outcome, Lipton plans to duplicate the ControlLogix-DeviceNet architecture for three similar conveyors. Because of the efforts made in specifying the right equipment, Lipton will be able to duplicate the existing system.
"The design is there. We just have to copy and massage it to fit the other lines," Rock says. As a result, he estimates that the cloned systems will cost 60 to 70 percent less than the original due to reuse engineering. And that will give Rock and Lipton's technical staff ample time make their tea and sample it too.