This ran originally in Design News.

by Al Presher

Improving the effectiveness of human-machine interfaces (HMIs) by developing a standardized approach to the design of operator interface screens and the content displayed on packaging lines, plus increased access to diagnostic information, has become a priority f

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OMAC, the Organization for Machine Automation and Control, has been a key player in the past in championing new technology, including the emergence of standards for servo-driven machines in packaging. And now with the corporate electricity and automation group at Nestlé providing a catalyst for getting a global technology standard put forward, OMAC has started initiatives for HMI standardization, improvements in on-screen machine diagnostics, and standardized packaging user requirements. All these areas have defied standardization efforts in the past, and they could all contribute to simplified and more efficient packaging operations.

By linking ergonomics, navigation, and design, new HMI systems are able to display complex processes in a way that is easy for the user to understand and manage. The new OMAC standard goes one step further by defining a common look and feel between operator panels in packaging plants.

"We believe that standardization is imperative to improving our overall equipment effectiveness," Dr. Bryan Griffen, global automation manager at Nestlé and chairman of the OMAC Packaging Workgroup (OPW), told us. "We are fully committed to the PackML strategy, and we continue to support and develop this strategy through active participation in the OMAC Packaging Workgroup.

"We are developing complimentary tools and specification for application as part of our PackML strategy," Griffen said. "These include HMI specifications, communications standards, and safety system integration -- all of which are focused on improving the operability and maintainability of our packaging systems."

HMI common look and feel

At an automation conference, Griffen showed 13 different HMI screens on a single packaging line with absolutely no common look or feel, including applications for inspection, weight checks, coding, and packing and transport functions. More than 200,000 HMIs are in use in Nestlé factories, and there are more than 70,000 people involved in packaging operations. But because the screens are all different, specific training is required for each type of equipment, costing both time and money.

To address this problem, the Nestlé packaging and automation groups have developed a standard HMI solution. Machine-specific requirements are displayed in the center of each screen, but a common template has been produced for a top menu bar, command buttons, navigation, and active alarms and event messaging. The goals of the template are to be user friendly, to allow operators to become more mobile across machines and lines, and to make more diagnostic information accessible from the equipment.

The OPW committees are focusing both on base technology and its potential benefit for applications. "We have tried to be practical and balance the focus on technical details around the standard with the benefits the standard would provide for end users, machine builders, and system integrators," said Thomas Doney, senior research engineer at the Nestlé Product Technology Center and a member of the OPW.

A primary goal is to harmonize the design of HMIs and to develop a consensus, especially among end users, on what the standard screens would look like and the content on each panel. Once end users complete the specification defining a specific set of HMI screens, machine builders will be able to reconfigure operator interfaces on different machines to meet the standard.

"The obvious benefit for end users, as the line is staffed with operators, is that on any given day, if someone calls in sick, someone else can cover that piece of the line," Doney said. "It's much easier for them to do that as they interact with the machine if the status of the machine looks the same as other machines on the line that they have worked on and, when a fault occurs, they are displayed in a similar manner."

On-screen machine diagnostics

A fundamental difference between process and packaging for Nestlé is that the company develops its process technology internally and therefore intimately understands and owns the intellectual property of the control code. Packaging machinery is developed by many different machine builders, and Nestlé does not want maintenance personnel accessing code that is not natively familiar.

Griffen called for machine builders to make all diagnostic and corrective actions accessible on the HMI, rather than inside the controller. He recognized that this will require a new effort from most suppliers, but he said it will add value by reducing downtime and improving efficiency.

This second element of the HMI transformation changes the way diagnostic information is displayed and will enable more parameters to be adjusted using the HMI interface. The engineering goal is for the standard to be implemented in a consistent way between different types of packaging machines with a familiar and almost identical program structure.

"What operations needs is a common look and feel so that a function, such as labeling a package, uses a set of HMI screens that are similar to the screens used to gather packages and place them in a box," said Doney. "There is a difference in the value-added steps performed as you move down the line but, for each of the process steps, an operator can walk up and the screens look the same and provide similar types of functional information. Plus when a fault occurs, the process of resolving problems is similar from unit operation to unit operation."

The PackML standard

The PackML standard becomes an important part of the solution and provides the basis for creating a set of consistently named variables and tags. Doney said food companies generally put a lot of emphasis on their own core competence, but historically there hasn't been an emphasis on unit operations downstream from the filler. If there isn't appropriate attention on the downstream operations, an entire line can be brought to a halt due to problems with the material or machine.

"As we have realized the need for more emphasis on end-of-line operations and a specific control strategy for operations downstream from the filler in total, PackML starts to come into play," said Doney. "It provides solutions for interconnectivity between the unit operations, and by providing a communication structure to report information up the line."

He said integrators like PackML because they know that, as they go from machine to machine on the line, the faults will have a similar tagging format. Integrators can configure the line control to fit the application. Today, the first thing they often have to do is to review the internal structure of the programming for each machine and adjust the programming to access the information needed to implement the line control.

Many of these functions were not implemented in the past because networking technology wasn't where it is today. As networks have evolved and Ethernet has emerged as a connectivity solution between machines and upstream, it has opened the door for what PackML can offer in terms of line diagnostics. "Users can now have an expected performance of the line, composed of the product of its parts. On a given day, if expected performance drops 5 to 10 percent, it is easy to go back and identify the reason," said Doney. "We can find out if the problem has been fixed or not and if it is something that over time is creating a degradation affecting hitting the target."

PackML enables users to get information from each of the machines with enough detail to analyze what is contributing to downtime. The software is designed to help simplify overall equipment effectiveness (OEE) reporting, solve problems quicker, and prioritize resources based on where the data shows it will provide the most benefit.
The goal is to move away from needing an engineer or high-level technician investing hours into investigating why the line is stopping and the duration of the stops. All the information is in the control of the machine, and PackML becomes a tool to extract that information. "If it takes several tries to clear the jam, it might be the same fault five times with a one-minute duration or one fault with a five-minute duration. It's a lot to ask the operators to keep detailed records and also keep the line going," said Doney. "PackML has the potential for enabling better running of the line with a more flexible workforce that can move from unit operation to unit operation. With the idea of a common look and feel, they don't need to be retrained on specific machines to know status and fault information."