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TAU and Axalta at the literal core of e-mobility: electrical steel
To perfect the curing and subsequent bonding of the magnetic steel core of electric motors and optimize process efficiency, Axalta partners its Voltatex® self-bonding enamels with Tau Industrial Robotics’ LILIT® in-line, real-time curing process control.
How the lack of insight scares steel mills and punchers alike
For greater sustainability, industries such as e-mobility and renewable energy are advancing the development of higher performing, lighter and more reliable motors. The optimization of the magnetic steel core of electric motors plays a crucial role in these efforts. Steel mills, punchers and motor producers require superior quality of electrical insulation to minimize so-called iron losses in the electric motor and thus guarantee its higher output power and energy efficiency. Precise control of the curing level is therefore essential but has so far been impossible.
Let's have a look at the reality of two protagonists in the production of electrical steel: Frank, a steel mill operator, and Michael, a punching line operator. Frank’s day-to-day work is to ensure his team fully masters the compliance of what they produce, steel coil coated with pre-cured bonding enamels, with the quality requirements provided by his downstream customer, Michael. Michael, in turn, punches specific shapes out of the coil and stacks them using enamels to build the electric core of the motor that matches the requirements of the electric motor producers, his ultimate customers.
Every day, Frank’s line produces electrical steel coils at over 70m/min. A few times each day, Frank has a small sample cut from the production and taken to the laboratory to test the curing of the applied self-bonding paint. Testing then takes a few hours, during which Frank worries about that day’s production quality. Usually it is all good and he can end his shift relieved and happily send the pre-cured coils to Michael. But then every once in a while, it is not. Then all production of the day must be assumed to be of insufficient quality and must be discarded; and Frank gets the blame for the amount of scrap and wasted resources – imagine that the length of an electric steel coil may easily exceed 10 km!
Usually all goes well though, and the steel coil arrives at Michael’s punching process. Frank sent him all the specs with the compliance report – so far so good. Michael adjusts his line to these specs and now punches the desired shapes from the coil. To build the magnetic core of the motor, the punched shapes are stacked one over the other like a layered cake (where the cream is the insulating varnish) and baked in a curing oven. But today, when he tests one of the cores they produce, Michael realizes that it doesn’t have the required strength. The bonding hasn’t really worked – the curing level of at least some parts of the incoming coil must have been different to what Frank’s specs said. As a result, the magnetic cores are under or over-cured and will not comply with the specifications of the motor producer.
When an upset Michael then gets on the phone with Frank to complain about the curing defects, an embarrassed Frank replies “Look, Michael, I really tested as often as I could in the laboratory and you know it is usually all fine – I wish I could test 100% of our production, but I just don’t know how!”
Axalta and TAU partner up to get the most out of electrical steel coating
Axalta’s self-bonding paint is actually a brilliant concept: Voltatex®, this new, one-component, self-bonding varnish, allows the creation of a seamless magnetic core without any defects to the lamination stacks. Since the self-bonded magnetic core is more rigid and mechanically firmer, it provides better heat dissipation, prevents the generation of harmful eddy currents – localized electric currents that damage the efficiency of the iron core – and eliminates humming noise, which happens when steel laminations are poorly joined.
So far so good. The tricky issue is that the correct curing window for the self-bonded core sheet has very limited tolerances: an under-cured varnish can be squeezed out of the stacking, while the over-cured varnish might no longer bond the laminations. An optimized, uniform curing level and process control is thus paramount.
LILIT® now delivers just that: a peace-of-mind curing control in real-time, in-line and non-destructive – at the steel mill and at the punching line. It uses ordinary spectroscopy but jacked up with industry 4.0 artificial intelligence data analysis to identify relevant inconsistencies and defects of the coating. This allows Frank and Michael to set correctly or adjust their production parameters according to the target product specifications. It minimizes the possibility of poorly cured self-bonding composites and provides accurate insight (more than 95 percent) into the electrical steel coil coating. No more time-consuming and destructive laboratory tests. And thanks to Axalta and Tau, Frank, Michael and the electric motor producer are happy with the motor cores of bonded stacks made out of steel coil.
Shedding light on curing of self-bonding paint – making it work
Every steel mill and every puncher have their individual process requirements for the core sheet manufacturing, stacking and laminations. So tailoring is key. It consists of three steps: installation, calibration and education.
For installation, TAU engineers come on-site to work hand-in-hand with the plant’s process operators. After evaluating the premises and addressing the real operational and environmental conditions (e.g. temperature, humidity, luminosity), they indicate the right positioning for LILIT® and propose an optimal architecture of the process. The installation is then easily done by TAU within days depending on the number of control channels the user wants to run simultaneously. Electrical and network connections are provided by the plant operators. The LILIT® itself is just the size of a larger shoebox.
“Simplicity aligned with performance are the key aspects of how we try to upgrade the existing test reality. Our intention was to bring to life an automated process assessment and reporting tool with artificial intelligence capabilities that could continuously analyze operational data of curing to provide a concrete action for the electrical steel value chain – contributing to peace-of-mind of operators”, says Piero Degasperi, TAU’s CTO.
LILIT® relies on contactless spectrometric analysis to detect fluctuations in the curing level of self-bonding varnishes. The position of the probe must be as precise as possible. TAU work on-site until such precise calibration is complete and the probe firmly attached with the supporting holder. Nominal production parameters like core sheet speed, oven temperature and ventilation for the selected Axalta Voltatex® varnish are set up by the user. TAU engineer selects this signal as a reference spectrum. The acquired spectrum of one line can later be used for further channels in case of multi-channels installations.
The education step is the speed-run: LILIT® is taught how to define whether the polymeric surface is undercured, overcured or just properly cured. This is done in close collaboration with the user’s quality department. From a range of curing samples for each type of Voltatex®, LILIT® can learn the qualitative difference between good and bad curing level of the core sheet.
The system is now fully operational and able to identify relevant coating inconsistencies and repetitive defects in real time. Any minimal variation from the target characteristics will be recognized in less than 15 seconds and result in a call for corrective action by the user. Incoming quality values are continuously correlated through the AI engine – and all this without any physical interference or damage caused while testing.
LILIT® is capable of quality tracking on both fixed and moving surfaces assessing coating uniformity across the entire coil. Immediate feedback reduces start-up time e.g. after varnish changes or coil changes.
Crucially, operators can use cloud-based remote access to get comprehensive, real-time insight into their production flow within selected period of time and have access to it anytime and anywhere! Its operating software is aimed at simplifying production process management and quality control by providing ongoing but lightweight feedback on curing characterization. It generates values online and creates visualized data reporting that can be automatically clustered, backed up and filed.
Once operational, the system’s ongoing machine learning based on the operational data assists the steel mill or the puncher to improve curing processes and eventually allows predictive suggestions for production adjustments, coil changing, maintenance activities or general planning.
“Our joint industry innovation efforts for electric mobility and renewable energy are aimed at delivering higher quality motors with reduced resource consumption and higher productivity, moving from traditional to a sustainable and smarter manufacturing. To simplify the work life of operators is at the core of what we do”, say Axalta’s Global Manager Electrical Steel Coatings
Andreas Vendler and Tau’s CCO Filippo Veglia.
