By Phil Burgert
Minimizing a machine operator’s interaction with his machine’s panel display while still providing proper access is an important objective of machine manufacturers and their automation suppliers. The goal is to keep the operator on task of producing goods, not trying to discover and diagnose malfunctions.
Similar requirements apply to access allowed for maintenance tasks and remote monitoring that allow review of operations without unnecessary production interruptions.
Simple, Flexible, Safe
“Ninety percent of the information required is on the one and only screen the operator needs to look at,” says Bill Richardson, electrical design supervisor for Prodomax, a designer and manufacturer of automated welding and assembly systems in Barrie, Ontario.
Richardson says 80% of his company’s robotic zones and cells are equipped with an operator panel and his company generally uses standardized screens. “For operator access—not access for a maintenance person or anyone else—the screen is available with messages and faults automatically that are generated automatically,” he says.
George Schuster, who worked on the Prodomax project as business development manager for automotive solutions at Rockwell Automation, notes that “passive,” “configurable,” and “lockable” were central designs elements, and he touts them as the fundamental guiding principles for panels and how people interact with a machine.
Passive design involves safety systems that workers are not required to engage, such as pressure mats and light screens, says Schuster. “An untrained person should not be harmed just by walking through a door, for instance,” he says.
Configurable system design, adds Schuster, creates modes of safe operation for enabling or disabling portions of a machine that can be used in a variety of situations, such as maintenance tasks. “This is a strategy to remove any incentive for the user to bypass the system,” he says. “Most people bypass safety systems because they have to get their jobs done.”
Lockable system designs allow an operator, maintenance worker or technician to configure a system for a certain mode of operation and place a personal lock on that configuration, to ensure that no one from outside the machine can access it. “A lockable system is a much more expeditious way to get in there, lock the system, lock the gate open, do the repair, get out, and get that machine running again,” he says.
“We don’t require the operator to go through great detail to find out what’s wrong with the machine,” says Richardson. “If for any reason that machine comes to a stop in its normal operation, it is our responsibility to make sure we have generated the message to the operator why that machine has stopped.”
The trick is to let the system provide the information. “We don’t need the operator wondering what he should do next, what screen he should open up, should he be looking for a sequence screen or anything like that,” says Richardson. “We generate the messages to keep the operator on track of his job, not troubleshooting or diagnosing an operation.”
WHAT YOU NEED
Richardson emphasizes that Prodomax designs its systems so the HMI is wherever the operator works (Figure 1). “He needs to look at that screen at the same time he looks at the process or the function he is performing,” says Richardson. “If the operator is loading multiple components into a fixture and a light comes on because he’s not getting all parts present, he needs to be able to look over and see what is missing. You shouldn’t have to walk out of the area to see that information. He has to be in the area of his work envelope.”
Prodomax considers it important to provide information on a single screen, to keep the operator concentrating on making parts, rather than diagnosing other issues. “We’re building the machine to make parts,” says Richardson. “The more time an operator spends diagnosing or finding out what is wrong, that’s time spent not making parts.”
Access to operator panels can be granted in a number of different ways, including magnetic card swipe, barcode, optical scan and inductive read systems, explains Mark Witherspoon, director of North American automotive operations, Euchner USA. “However, not all systems are created equal, meaning some systems are not as secure as others, and some are not designed for certain environmental conditions,” he says.
Barcodes are not secure because the barcode can be copied easily on any available flatbed printer, explains Witherspoon. Magnetic card swipes are more secure, but are subject to damage and demagnetization—nuisance problems for the user, he says.
“Optical systems, such as fingerprint scanners, can be secure but are typically designed for a clean office-type setting and do not work well in industrial environments that might have airborne dust, coolant, oils or other industrial contaminants that can create a film or cause a smudge on the scanner lens,” says Witherspoon. Inductive transponder coding systems, the same technology that is used in automobile ignition systems, are very secure and are designed specifically for plant floor conditions.”