Interview: Revolutionizing UCI hardness testing for Lean Manufacturing
By Yan Yan, March 12, 2019,10:00 am CEST
Revolutionizing UCI hardness testing for Lean Manufacturing
The underlying principle of the Ultrasonic Contact Impedance (UCI) method for hardness testing was invented more than 50 years ago. Advances in technology in recent years have enabled Proceq to improve not only the UCI testing probe, but also the entire measurement process. We sat down with Ms. Yan Yan, Product Manager of Equotip, to find out what this means for the quality assurance operations in manufacturing.
Yan, tell us more about UCI—what makes it such an important method for hardness testing?
And how does UCI work?
YY: A Vickers-shaped diamond indenter is mounted at the end of a long thin nozzle and on top of a piezoelectric element. The piezoelectric element vibrates longitudinally at a specific frequency, moving the indenter back and forth like a microscopic jackhammer. The operator positions the indenter perpendicularly to the surface of the test piece and starts pressing the probe against the surface with gradually increasing force. At a predetermined amount of force, a mechanical end switch inside the probe triggers a measurement. Depending on the hardness of the test piece at the measurement location, the vibration frequency changes. The frequency shift is then converted into hardness in the Vickers scale. This is how traditional UCI probes have always worked.
Thank you for the explanation. You mentioned “traditional UCI probes”. Why did they need to be improved?
YY: Traditional UCI probes have two main disadvantages.
Firstly, the purely mechanical working principle of traditional UCI probes only allows one fixed load per probe. However, different applications require different UCI test loads. And, it’s not rare nowadays for manufacturing operations to involve numerous types of applications. In that case, the user must carry around different probes. Of course, this means that all these different probes must also be procured, tracked, maintained, calibrated... I’d rather have a single probe that does it all, wouldn’t you?
An Equotip UCI probe can operate as an HV1, HV5, or HV10 probe, depending on the setting. These three test-load settings cover the vast majority of field applications. So, with Equotip UCI you carry one probe in your pocket, and you’re set.
The second disadvantage of traditional UCI probes is what we call the “operator dependence” of test results, and it is caused again by their purely mechanical working principle. One of the most important drivers of quality for UCI measurements is how the operator applies force during the loading process. Traditional UCI probes leave the operator entirely unguided, because there is no feedback until the mechanical switch triggers at the single predefined load. So, we took a look at this and thought that it’s time to do what our competitors haven’t done in decades: make the UCI testing method as “smart” as it deserves to be.
YY: With sophisticated, miniaturized sensors and electronics. Sensors measure and monitor the test load over a wide range corresponding to HV1 to HV10, i.e. from a 1 kg force to a 10 kg force. The sensors allow real-time monitoring and recording of the loading process. The Equotip 550 and Equotip Live platforms use those data to provide real-time guidance to the operator, for example with helpful messages during the test load application. This instills confidence and improves the quality of UCI test results. And it also makes it possible for inexperienced UCI users to learn and become productive faster.
Can you elaborate further on how you came up with this new product?
YY: Sure. When we developed our Equotip UCI probes, we looked at the traditional UCI probes and identified the disadvantages I mentioned. Then we took a step back and looked at the entire measurement process with UCI through the lens of Lean’s “eight wastes”. What we found was surprising: there are at least five evident wastes along the process.
What do you mean by “waste”?
YY: In Lean Manufacturing, “waste” basically means any non-value-adding part of work. So, as part of all of our product development projects, we aimed to identify and remove different types of waste, in order to improve the entire process and user experience end-to-end.
And what did you find?
YY: We found at least five different types of waste to which traditional UCI probes contribute: defects, unnecessary waiting, motion, transportation and inventory. Let me explain two of those:
To start with the most important one: defects. As I mentioned, traditional UCI probes make it impossible to quality-assure the measurement process itself. Therefore, it’s inevitable that unskilled operators make mistakes during the loading process. These mistakes can cause wrong readings that cause manufacturing defects to go unnoticed.
Basically, all possible sources of human error along the UCI testing process are sources of defects, too. It’s not only the force application itself. It’s also mistakes when writing down the test results on a scrap of paper—or losing the scrap itself! Or mistakes when creating a report manually. Or mixing up the files of different measurements on a USB stick or on your PC. To err is human; so, it was important for us to remove such sources of human error from the end-to-end process.
What’s the second type of waste you found?
YY: Waiting, in other words: any unnecessary lead time. Waiting creates other wastes, too, so it’s very important to attack it first.
Let’s imagine that you are a quality inspector in a manufacturing plant. With the traditional approach, you would make many UCI measurements over a period of hours. For example, six hours later, you would sit down to prepare a report, based on which you will evaluate if everything is going well. But what happens in the meantime? In those six hours, manufacturing operations will continue to produce inventory that may have defects. If there is indeed a problem, it will only be caught after you have compiled a report and identified abnormalities. And then, you will either have to scrap all the 6-hour waste or rework it—what a waste of time, resources and money!
And how do you reduce the waiting with Equotip?
YY: Firstly, the user interface of our mobile app is highly visual and intuitive, so if something is indeed wrong with the test piece, you are likely to see it during measurement. Secondly, we cut down the lead time between measurement and insights. With the Equotip Live app you can generate a report within seconds, right after you have measured, and with a couple of taps. You can then share this report with colleagues instantly, to reach a conclusion and take action on the shop floor.
And thirdly, we even make it possible to see the measurement data live as it is recorded and streams in, from anywhere, anytime, with a web interface. This is something that’s increasingly popular with customers who are digitalizing their operations, and where decisions can be supervised remotely.
Very interesting – can you provide a practical example?
YY: Sure. One of our US customers is running a metalworking facility and used to own a single, wired UCI testing device from a competitor. The only one who was allowed to use this device was the quality manager, who spent most of his days running around the facility, measuring here and there, and generating reports on his desktop PC. Nevertheless, there was still plenty of rework and scrap.
In recent years, however, our customer’s business started growing at a rapid pace, and what used to work didn’t scale anymore—they would have needed to bring onboard another quality manager and to purchase another UCI device in order to provide the needed capacity.
As it turned out, though, it made more sense both economically and in terms of quality assurance to distribute the testing effort and bring it closer to the source of potential manufacturing defects. This means that every metalworker on the shop floor would become a driver of quality assurance, on the spot. Actually, this should not be surprising to fans of Lean Manufacturing, who know all about “one-piece flow”.
Our customer now owns a small fleet of Equotip Live UCI probes that his metalworkers carry around in their pockets for instantaneous tests, at any time. Meanwhile, the quality manager uses the Proceq Live web interface from anywhere he wants to monitor the data as they stream in from all metalworkers’ mobile devices. This means that he can respond to deviations within a matter of minutes, not hours. Less rework, less scrap and less warranty risk mean that the fleet of Equotip Live UCI is more than paying for itself.
That’s very insightful, thank you! Any parting words?
YY: Take a holistic view of your business’ operations and think about how you can make things better, faster, and smarter – Equotip helps you become digital. I invite everyone in the manufacturing industry and with an interest in quality assurance to check out our website and especially the Equotip product family. We pride ourselves in not only being the inventor of the Leeb testing method, but also in being the only company with a complete offering of portable hardness testing solutions. So, even if UCI is not right for your application, you will certainly get things right if you choose our Equotip Leeb or Portable Rockwell solutions.