Wednesday, October 22, 2014

Business Value and the HMI

By Patrick Weber, MESA International Technical and Education Committee member

This blog post may be sailing into stormy waters, but today I’m putting on my bean-counter hat and challenging conventional wisdom with regards to human-machine interfaces, or HMI for short. This post is somewhat in response to the LinkedIn article “Look at all them pretty pictures” by Gerhard Greeff of MESA International. (As a side note, if you are in the manufacturing automation industry and are not following Gerhard on LinkedIn, you are the poorer for it!) But my hope is that we can start a conversation about the true business value of graphical user interfaces in today’s manufacturing environment.

Lifecycle Cost

How much are you paying for your HMI? As an example, there was a new machine build for a discrete unit tray loader; the company had many older versions of this machine, but this would be built with a modern PLC and touch-screen graphical user interface (GUI). Implementation of the HMI took over 300 man-hours, and training operators, electricians, and mechanics to use the new interface took even more time. Then came maintenance costs associated with making the complex GUI “more user-friendly”. Using this example, lifecycle cost = initial cost + integration cost + maintenance cost. (NOTE: Writing the actual control software for the PLC took significantly less time than creating the HMI!)

Business Benefit

What value are you getting for your HMI investment? One way to approach this is to look at the incremental value provided by the GUI over non-GUI equivalents. This was fairly easy to do in the unit tray loader example, because there were several implementations of the non-GUI machines to with years of run-time. The examination proved disappointing from a business perspective; there was no measurable benefit from the GUI-based UI. In fact, the opposite was true; operators, mechanics, and electricians found the user interface confusing and non-intuitive. There were even requests to replace the GUI with the older push-button panels found on the other machines. The expected benefits of the graphical HMI included faster diagnostics when downtime occurred, better insight into machine performance, and easier ways to change machine settings. These proved to be no better than the non-GUI approaches. Business benefit: less than zero!

I realize there is a danger of over-generalizing based on a single example, but I do wonder if this truly is an over-generalization. Manufacturing organizations may have hundreds or thousands of assets on their plant floors, and if no one questions the value of the de facto approach then the drive to implement graphical human-machine interfaces will provide no return on investment and actually decrease the competitiveness of the organization!

A Smarter Approach

The problem isn’t inherently one of GUI versus non-GUI; it is the custom nature of the prevailing approach to HMI implementation. One of the enabling forces of the industrial revolution was standardized, interchangeable parts. Prior to this concept, every part needed to be custom-made for its application. Replacing parts meant getting a skilled craftsman involved. This offers insight into how the custom user interface problem might be addressed. 

What if, instead of spending hundreds of man-hours developing a new UI for each machine, there were a standard UI that could be customized in less than a day? Or even require no customization whatever? It would provide the same basic operations, independent of machine implementation, so training personnel would be very easy – once they’ve learned to run one machine, they have the basic skills to run any machine based on the standard UI. 

It would not have all the intricacy of a custom UI, but those features are seldom used anyway and could be provided via alternative approaches. And those alternative approaches may ultimately prove more valuable anyway, because they could involve the use of mobile technology which would lessen the requirements for fixed HMI. This is exactly the approach ultimately taken by the company in my tray loader example. While visualization standards are important (and again I’ll reference Gerhard’s wonderful article), true business value will only be realized when an organization-wide standard UI is implemented.

Your thoughts and comments are welcomed!

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