As you look at how your machines are operating on the plant floor, overall equipment effectiveness (OEE) provides a great means of evaluating how truly productive they are. Measures of availability, performance and quality come together to deliver insights on how best to improve your manufacturing processes. An OEE score of 100 percent means you’re manufacturing only good parts as fast as possible, with no stop time.
The Organization for Machine Automation and Control (OMAC), which was formed in 1994 to help manufacturers share best practices to improve efficiency and profitability, has been working on standards for calculating line OEE and machine efficiency using PackTags. The group has also been working on PackML human-machine interface (HMI) guidance, including implementing standard stack lights that visually identify a machine’s PackML state. At the Automation World Conference & Expo last month in Chicago, Chris Hough and Patrick Toohey brought attendees up to date on the work being done.
OMAC’s work on OEE implementation is focused on OEMs and end users, providing open-ended information about machine- and line-level metrics. “We wanted to make sure the information we got was as accurate as it could be,” said Hough, general manager of ProMach’s ZPI division. He stressed the importance of accuracy, simplicity, and standardization, noting the need to send information across various types of equipment and production lines. “Companies are doing pretty exciting things with data collection, but down at the machine level it has to be accurate and easy to use.”
The three important measurements for OEE are availability, performance and quality. “When you combine those three numbers, it’s very, very difficult to make that a more favorable number than what it is,” Hough said. “We looked at all the implementation challenges throughout the years. What can we do to address some of these?”
Each machine takes a whole lot of information back and forth to record OEE. So rather than just looking at the machine-level OEE, the group decided to take a step back, looking at data stewardship and getting a better understanding, for example, of how upstream or downstream problems might cause a hit on availability. “To effectively calculate line OEE, we need to send information back and forth across the line and measure performance from critical assets,” Hough said.
OMAC focused on using PackML and PackTags for the OEE guidelines. PackML is a communication standard for the control of packaging machines. PackTags are used for machine-to-machine communications and can also exchange data between machines and higher-level systems like the manufacturing execution system (MES). “PackTags are a great jumping off point to understand what’s out there and what’s available,” Hough said.
Standardizing OEE implementation provides benefits for both OEMs and end users. For OEMs, it makes sense to take data and feed it up. “It empowered OEMs to create standard blocks of data the same on every machine,” Hough said. “They don’t have to keep creating code, and it can be done by higher-level systems.” Using the domain knowledge of the OEM will also enable a lot more granularity, he added.
For end users, “each company will have their own internal standards as far as what they consider OEE,” Hough commented. The guidelines provide a way to call those out so any users are aware of what that calculation is. They enable direct comparisons between pieces of equipment, he added, and ensure that calculations align with the needs of the business.
HMI, stack light standards
It’s the operators OMAC is really looking out for with new standards aimed at HMI, stack lights and pushbuttons, according to Patrick Toohey, lead HMI designer in Mettler Toledo’s Product Inspection division. Operators have to keep the line running, replenish materials, manage changeovers and optimize efficiency. But they’re faced with a confusing array of sizes, shapes, button and layouts on the HMI.
“Some are ugly, and a lot are not useful,” said Toohey, a self-professed usability snob. “They say they’re user-friendly, but they’re really, really bad.”
Despite what some HMI designers think, there’s more to user-friendliness than not crashing. The disciplines that are missing from an engineering curriculum are the psychology and graphic design classes that would actually make those HMI screens more usable.
Aimed at those engineers, the new OMAC documents provide standard components for stack lights, pushbuttons, PackML state diagrams and interface navigation, offering guidance for usability and graphic design. “There are simple things that you can apply to improve the interface,” Toohey said.
At the end of the day, he said, it’s all about the operators. They want to make it easier for operators to be efficient and keep the line running. They want to make sure the interface is consistent from machine to machine so that operators can move from line to line. They want operators that are equally effective under abnormal conditions. They also want operators that are satisfied with their work so that they’ll stay.
“To achieve that, we need engineers who care and who understand the challenges,” Toohey emphasized. “Usability is when an operator can just sit down with the interface and can use it. Engineers need to accept the fact that usability is their responsibility.”
But engineers need guidance on the scope of usability and even what it is, Toohey added. To that end, OMAC created a PackML HMI Working Group in 2018 and has now introduced that guidance. The guidelines map PackML states to stack light and pushbutton states, defining how lamps and buttons should work. This year’s updates to the guidance also standardize state model visualizations, including requirements and accommodations; and provide a navigation template, including guidance on standard screen content, layout and design.
Download the PackML Implementation Guide at omac.org.
