Over the past decade or so, recognizing the growing importance of such data to customers looking to integrate plant floor operations with enterprise applications, PLC vendors have been offering solutions to improve communications with their devices. Rockwell Automation, a world leading manufacturer of PLCs , for example, offers its customers a software connectivity solution built on the Object Linking and Embedding for Process Control (OPC) standard to enable connectivity between human machine interface (HMI) software packages and Allen-Bradley PLCs. One OPC connectivity solution, which Rockwell Software offers is its RSLinx software. The RSLinx connector is an OPC Data Access server that provides communication services for Rockwell Automation’s Allen- Bradley brand of PLCs.
Once a user builds an interface application with an HMI development tool, the RSLinx software would provide them the drivers and other connectivity components that enable communications with the PLC. Users are then required to purchase individual RSLinx copies for every machine on which they wanted to run their application, along with annual software maintenance fees for each copy.
Trien Dao, senior software engineer at a major medical device manufacturing facility in the Minnesota Twin Cities region, evaluated the cost of using RSLinx server to communicate with numerous Allen Bradley PLCs deployed throughout the plant, but the fact that license and annual maintenance fees would be required for each copy set him searching for an alternative. One tool that he discovered automated the development of OPC applications.
Working with OPC can be complex and requires specialized experience and the software that he discovered simplified the process of working with OPC significantly, but it still required purchase of individual RSLinx copies and maintenance fees, along with the cost of managing yet another license, so this was far from an ideal solution. “With the CimQuest INGEAR solution, once we developed the interface, all we had to do is export the DLL to any machine on which we wanted to run it. We didn’t have to pay additional fees. We have PLCs running on many machines, so not having to buy additional licenses for each one is a tremendous cost savings, definitely in the six figures,” said Dao.
NET.LOGIX provides us with a direct communication channel to the PLC and does not require third party components, drivers, APIs or tools, such as OPC Servers. This simple programming model contributes to faster response times and ease of use. “In addition to the cost savings, we found response time for the applications we created with INGEAR to be much faster by seconds than other applications we have created,” said Dao, reporting also that he fully expects such significant improvements in response time to improve output as well.
With the INGEAR software Dao found both a solution which eliminated runtime fees entirely by enabling connectivity without RSLinx. At the same time, the solution overcoming the complexity of OPC, simply by eliminating the need for it and utilizing the familiar .NET programming. Using .NET brought with it the added advantage of enabling him to assign programming task to.NET programmers who did not necessarily have an understanding of PLC control logic.
Allen-Bradley brand PLCs are only one of the number of brands that Dao is looking to communicate with. So impressed was he with the economics and the performance on the Allen-Bradley PLCs, he is now evaluating expansion of runtime free communications development across other brands of PLCs that are deployed in the plant, and expects similar gains in cost reduction, response time improvement and ease of use.