By Phil Burgert
[Read the second part of this article on the the use of touchscreens for discrete manufacturing operator interface applications. See Touchscreen Advantages-Part II]
The growing use of touchscreen-based human machine interfaces for discrete manufacturing is an indication of the advantages this type of interface provides when compared to traditional interfaces like keyboards and mechanical buttons.
Some of the advantages cited by the users and vendors of these technologies include increased flexibility, smaller space requirements, cost differentials, wiring reductions and reprogramming ease.
Good in Tough Situations
Properly selected touchscreen panels offer advantages for use in difficult environments. “Mice need to be clean for the optics to work; the old roller ball mice were even worse,” says Bob Meads, president and senior software engineer for Odessa, Fla.-based system integrator iQuest Inc.. “In a factory setting, dust and dirt from the process get into keyboards, which then can fail. “I’d hate to find that a key was stuck or not working when trying to enter a critical set point or operation step, and my process was adversely affected.”
In clean environments where a sophisticated interface is required, Mead says traditional interfaces are sometimes used, but “industrial panels certainly are called for where traditional PCs with fans and mechanical hard drives are likely to fail due to the environment,” he adds. “Environments with temperature extremes, liquid/fluid spray proximity, vibration and high airborne particulate counts are where panels are commonly deployed. Fans and hard drives just don’t hold up.”
His other considerations include proximity to the process and the workspace available. “Sometimes, there is no flat space for a monitor, keyboard, mouse and PC tower where the operator needs to be for efficient or even safe use,” adds Meads. “Since we can more easily deploy small touch panels for simple jobs, this makes panels the only choice.
Workers wearing protective gear or in a dirty environment could find it hard to use a mouse or pointing device. “However touch panels might not work for very dirty environments where the worker wears gloves or whose hands will be very dirty or greasy,” cautions Meads. “In these cases, some panels come with function buttons that respond to pressure rather than electronic sensitivity to allow gloved workers to operate the application.”
As demand for touchscreen operator interfaces for industrial machinery grows, the products offer technologies such as wireless mobile touchscreen panels and even safety-rated versions that include wireless e-stops, says Paul Ruland, S7-200 and Logo! product marketing manager in the automation and motion division of Siemens Energy & Automation.
A big advantage of touchscreens is space savings “to allow more devices and more data to be displayed in a smaller area compared to traditional hardwired pilot devices such as panel meters, gauges, annunciators and chart recorders,” says Ruland. “Touchscreens save manufacturing costs for machine OEMs by reducing the number of wired signals required to terminate, power and troubleshoot traditional panel devices. They also reduce the amount of additional I/O points on the controller for these devices.”
With a typical HMI application you’re doing either serial communications or some other bus communications to a PLC, whether it’s Ethernet or something else, says David Kaley, product marketing manager for HMI and networks at Omron Electronics. “When you’re using all those pushbuttons and meters, you’re actually wiring into I/O points on a PLC,” he reminds. “If you think about that, you’re adding cost to your PLC because need to have I/O points—analog and digital—dedicated to the controls on the panel.”
Operator interface software tools for touchscreens let engineers develop graphical screens without needing to develop hardwired computer-aided design drawings or wiring diagrams, says Ruland. “The graphical content displayed on touchscreens also can be more intuitive than traditional panel devices and be more easily customized with preferred labels and designs that help reduce training and maintenance costs,” he adds.
Talon Manufacturing of Spring Park, Minn., uses two types of 12-in. display panels from Beckhoff Automation for all-in-one control and display on its bagging systems for microwave popcorn and other snack food. To complement the hardware, Talon used HMI software to design a high end, easy-to-use array of push buttons, menu screens and display graphics. The software also provides a visual representation of system monitoring.
“The advantage of the touchscreen is that you create a lot of flexibility,” says Dennis Hohn, president of Talon. “For a machine of this complexity you need multiple screens, engineering screens, and graph charts. Without a touchscreen, you’d need a huge display with buttons. It just shrinks the system and the space needed to run the machine and provides a lot more information.” The extreme flexibility of the touchscreen setup on the embedded PC includes the possibility of monitoring vision system images through the screen, adds Hohn.