Choosing the right HMI: Three considerations to help optimize efficiency and productivityWritten by Jesse Benefiel, Red Lion Controls Wednesday, 19 October 2011 13:09
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.
1. 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 of the automation equipment in the machine, such as barcode 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.
2. 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.
State-of-the-art HMIs are communications centres that link 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 allow variables to be analysed 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 needs 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 that data is 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.
3. 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. E-mail 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.
Jesse Benefiel is product manager-interface with Red Lion Controls.
This article originally ran in the October 2011 issue of Manufacturing AUTOMATION.