Its functionalities also assure safe and secure manufacturing operations and provide assistance in disaster recovery.
“If you’re dealing with software, you should have version control,” says William W. Persyn, senior manager at MDT Software (www.mdtsoft.com), Alpharetta, Ga. For companies with many devices, such as programmable logic controllers (PLCs), human-machine interfaces, robots and other traditional factory gear, version-control software is particularly advantageous, he says. “Typically, for manufacturers with more than 30 devices, we find the value statement is very high.”
Version control is part of software-configuration management tools used to handle digital assets, says John Walker, principal product consultant for Alameda, Calif.-based Perforce Software (www.perforce.com). “It provides the infrastructure to track, manage and secure companies’ software-development efforts. If a change needs to be made to source code or a document, that’s an event we track and attribute to whoever made the change. We can go back to any point in time and see what was done, and recover that information.”
Proprietary? No problem
Both proprietary and open systems are compatible with version-control software. Computer numerical controls are quite extensive, as are PLCs, “because they are proprietary devices and have multiple languages,” Persyn explains. “Typically, manufacturing devices are proprietary. What we have done is create special drivers to work with different devices such as those from Allen-Bradley, Schneider, Siemens and others. With robots, some are proprietary and some are not. We have a universal module for devices that aren’t propriety.”
Version-control software can also be a useful maintenance tool, he adds. In a manufacturing facility, typically 3 percent of the PLCs’ programs are changed weekly, with changes being either ongoing maintenance or program-related, he says. “Sometimes the machine is down and some limit switch is not working. A maintenance guy will put in a blow-by that will skip over safety codes,” Persyn explains. “Often, if no one knows the change has been made, the PLC program will not be restored to its original state.”
Another maintenance example occurs when a battery goes bad on a PLC, causing facility downtime until that program is replaced. “You need to have the program accessible and easily loaded into the PLC. More importantly, you need to have the latest version of the PLC program,” he says.
Yet another situation often encountered is that PLC programs are different from the device’s current copy. Typically, that occurs because someone has gone online and made a change, he says. Likely, those changes are never stored for future reference, Persyn notes.
To avert discontinuities in the historical record of revisions, old versions of programs must be stored. “We take it a step further, though. Using our MDT AutoSave, we actually go out and interrogate the equipment. Overnight or at whatever frequency is specified, the software reads the programs in the PLCs and then compares that information to the last known program. The version-control software will copy the new program and store it and [then] compare it to the last one.
Launching version control is fairly simple. Required is software installation and then hardware configuration. “You would need a server and a couple of weeks of engineering and you’re good to go,” Perysyn says. However, his company uses a “shrink-wrap approach” that involves installing the software and then customization by users filling in the blanks.
Version control is becoming more prevalent, he says, “because there is more outsourcing of manufacturing support. Also, there are more regulations (e.g., pharmaceuticals, ISO and others) coming out that make version control attractive. Third, things are becoming more automated.”
C. Kenna Amos, [email protected]
