Choosing the right HMI: Focus on three factors to help optimize efficiency, productivity
Modern HMIs are more than just high-tech replacements for push buttons. They are tools with advanced capabilities that allow them to increase equipment productivity at little or no increase in the cost of the HMI. However, achieving that added productivity depends, in large part, on choosing the right HMI for the job. When selecting an HMI, system designers should consider how the machine or process could be improved by focusing in particular on three areas: integration, performance benchmarking, and remote management.
Increased automation through integration
Many HMIs are only the front end to a PLC. In some cases, a machine builder will opt to equip the PLC with a communications card so that the device can pass data to and from other equipment—for example, to an AC drive. All too frequently, that’s where the integration ends.
Today’s HMIs have the ability to communicate to numerous devices simultaneously, over a variety of protocols, allowing the machine builder or process engineer to fully integrate all the automation equipment in the machine, such as bar code scanners and position sensors. The ability to exchange data with the PLC adds an increased level of automation, while reducing machine or process downtime due to operator error.
When choosing an HMI, system planners should determine which devices in their processes are not currently communicating with the rest of the system. They should consider opportunities to increase system performance by automatically managing them through the HMI. An HMI should be selected that provides multiple-protocol support and contains the communications drivers required for those devices.
Continuous improvement through performance benchmarking
It’s difficult to know where one is going without a proper understanding of where one has been. More specifically, system designers first need to establish a way to track machine productivity or process efficiency before they can develop ways to improve it.
In many ways, state-of-the-art HMIs are communications centers, linking together automation components. The more advanced the model, the more powerful the data logging facilities that are provided. Further, computational capabilities through script languages enable the HMI to calculate downtime, uptime, overall equipment effectiveness (OEE), and more. Logging data, alarms, and operator activity allows variables to be analyzed properly, which in turn impacts overall efficiency.
System designers should determine if the facility would benefit from synchronizing machine data with the company’s SQL servers for further analysis by the ERP/MES system. If data need to be kept safe for long periods of time, consider simply synchronizing with an FTP server. Once the purview of full-blown SCADA systems alone, today’s HMIs typically are capable of performing these tasks automatically.
When selecting an HMI, it is important to ensure data are stored in a convenient format. Data stored in proprietary formats, or those unreadable unless processed by software plug-ins, only serve to complicate an otherwise easy task. Optimum HMIs log data in an IT-friendly CSV file format, allowing data to be viewed by most desktop applications. Digital signatures added to the log files can be used to validate data, should their authenticity come into question.
Reduced downtime through remote management
When selecting an HMI, system developers should consider how the ability to remotely manage equipment can increase the profitability of their processes—and the company. In years past, when maintenance teams were staffed for weekend and third-shift work, managing automation systems and equipment remotely was not usually necessary. Today, however, many companies have reduced their maintenance workforce to a few vital engineers. And they are on call overnight and on weekends in case of problems or breakdowns.
When no engineers are present, operators can’t immediately obtain help in the event of a problem. If the operator is uncomfortable with a system or machine acting out of the ordinary, he may halt production unnecessarily or, worse, may choose to continue operating the machine until it is damaged, resulting in more downtime and added expense.
Today’s HMIs routinely incorporate the ability to manage equipment and processes remotely. Email and text-messaging provide a means to communicate process anomalies and impending equipment failure to on-call engineers and production supervisors. Embedded web servers enable remote monitoring and control via PCs and smart phones, allowing the engineer to determine if a machine can continue operating safely without needing to visit the site. In some cases, the engineer can resolve the issue without ever leaving home.
Sophisticated features such as those discussed here are not just for those willing to make large investments in PC-based HMIs running SCADA software. These features are migrating into dedicated HMIs. Even a small 6-in. touchscreen can be equipped with capabilities beyond those of PC-based systems of only a few years ago. They are ideal, cost-effective solutions for many applications.
For more information about HMIs and the selection concepts described here, visit the Red Lion Controls website at www.redlion.net.