Smart systems improve line efficiency (sidebar)

As the name implies, Supervisory Control and Data Acquisition (SCADA) software performs two separate but somewhat interconnected functions. Obviously, the "DA" part of SCADA refers to data acquisition (see main story). The other part of SCADA is control. SCADA systems typically consist of software that runs on one or more PCs. The PCs communicate with a network of packaging machine programmable logic controllers. The SCADA system can also perform some control of the entire line, either coordinating the individual PLCs or controlling the sections of the line that are in between each PLC-controlled machine. Or SCADA PCs can simply act as a window into each PLC on the line. Such PCs allow an operator or mechanic to interact via human-machine interface (HMI) screens that simulate a control panel. This central, graphical HMI permits operators to obtain information from and change settings on multiple machines. It can also gather and summarize performance data that's not tracked by individual machines. Supervisors can run the same HMI software on their desktop computers in their offices to monitor real-time line performance. One note about the term "HMI." The touchscreen operator interface that comes with many modern packaging machines is also considered an HMI. The difference is that such "embedded" HMIs-incorporated directly into the machine itself-are primarily intended to communicate directly to a single packaging machine's PLC, although there are now embedded HMIs that will display information from other packaging machines' PLCs.