Success story Mubea

Appropriate Temperature Management Required

The batteries of electric vehicles are demanding when it comes to their working climate and do not tolerate temperature extremes. To keep them within a comfortable climate in both hot summer and frosty winter conditions, a powerful thermal management system is necessary. Many of the current batteries are easily flammable and heat up during charging, making the cooling function particularly important.

Excessive battery temperatures lead to capacity losses and, in extreme cases, can even result in thermal runaway. Conversely, low temperatures negatively impact the efficiency and capacity of the battery, increase resistance, and promote the formation of lithium dendrites (lithium deposits), which can shorten the battery's lifespan and lead to the failure of individual battery cells. However, constant cooling limits the charging speed of the battery. Therefore, battery manufacturers rely on so-called immersion cooling. In this type of cooling, a thermally conductive but non-electrically conductive liquid envelops the battery. This so-called active cooling plate is an aluminum element in which the liquid circulates. The globally operating specialist for innovative lightweight solutions, Muhr und Bender KG (Mubea), headquartered in Attendorn, has further developed the technological capabilities of the proven roll-bonding technology to manufacture large-volume cooling plates for automotive battery systems. This results in new advantages in the production of the plates, particularly regarding the shaping options and flexibility of the cooling channel layout.

The family-owned company employs over 14,000 people at 50 locations in 18 countries and has continued its growth trend despite ongoing global crises, exceeding the €3 billion revenue mark for the first time in 2023. In the coming years, Mubea aims to shape the mobility transition with intelligent lightweight solutions. Investments in the 2023 fiscal year have prepared the company for the transformation of the automotive industry. Components for high-voltage storage and products for electric motors, as well as new micro-mobility solutions, will complement the existing product portfolio. Core products in the chassis and body areas are to be adapted to the new requirements of electric vehicles.

This also includes the continuous further development of the roll-bonding process for demanding and economical tempering applications. This continuous hot rolling process can produce both high-quality flat cooling plates and complex-shaped cooling parts with cost savings of up to 20 percent.

In roll-bonding, two aluminum plates are rolled out, smoothed, and brushed simultaneously. A channel arrangement is stamped onto the lower strip using screen printing, preventing the joining of the coils at these points locally. The strips are then heated to over 400°C in two continuous furnaces, coupled, and hot-rolled under a pressure of 600 tons. This perfectly connects the two strips. After an annealing phase at a temperature of 450°C, the strip is cooled, dried, and cut. The bonded plates are then inflated and later bent. To ensure that no leaks are associated with the cooling circuit, the plates are subsequently measured and checked to ensure efficiency and the long-term reliability of the entire battery system.

Clamping with Vacuum – The Trick is in the Detail

Three years ago, Mubea began the project of manufacturing cooling plates. For quality assurance of the cooling plates, the company relies on optical measurement using the ATOS 5X system from GOM, a company of the Zeiss Group. The system provides highly precise data for tools and stamping, bending, drawing, pressing, and forming parts, as well as for plastic parts. The full-area 3D scans allow for comprehensive process and quality control, making errors and defects visible, which enables early corrections and process optimization. Additionally, the ATOS 5 system can also be used for efficient series production monitoring and assembly analysis. During scanning, up to 2 x 12 million coordinate points are captured. The system uses an integrated Laser Light Compressor to generate ultra-bright, even, speckle-free light. This enables measurement fields of up to 1,000 mm with very short exposure times. The appropriate inspection software guides users through the entire workflow, from measurement to evaluation to the inspection report.

A key factor in inspecting the cooling plates is also the clamping device, as only secure workpiece clamping guarantees the repeatability of measurements. The proposed approach of “Virtual Clamping” did not work as hoped. Project manager Andreas Rosum from Mubea Tailor Rolled Blanks then contacted WITTE Barskamp, the technology leader in clamping, positioning, and measuring devices. Benjamin Ostrowski, Sales Manager Central Europe at WITTE, explains: “In early 2023, Andreas Rosum and Markus Brüggemann contacted me with the task of clamping a relatively large sheet as freely as possible. There were defined clamping points that should ideally not lie directly on the sheet because we needed the surface and space for optical measurement. Therefore, a standardized clamping device was not an option.”

With this task in hand, Benjamin Ostrowski gathered his colleagues from the project management office. “The challenge was to measure the flatness of the plate, ideally with a clamping setup of 40 points,” explains Benjamin Ostrowski. “That’s how the idea of using our vacuum technology with suction cups came about.”

WITTE is considered the market leader in precise clamping devices in combination with vacuum, hydraulics, and pneumatics. Among other things, they have already designed vacuum clamping devices in 3D geometry with movable segments for clamping aircraft fuselage segments. In addition to standard and custom vacuum clamping solutions, they also provide all necessary components, such as simple ejectors, vacuum pumps, rotary joints, hoses, solenoid valves, and more.

At the beginning, they worked out different clamping possibilities based on foundational studies before starting the concrete project with a smaller cooling plate. Benjamin Ostrowski explains: “We received a test sheet from Mubea and first had to build a makeshift device to prove that it was even possible to clamp with our bellows suction cups. But our project management in vacuum technology did a great job. The tests showed that it works.” The sheet was to be held with a defined force (42 clamping points with 2.5 kilograms each). “It sounds relatively simple at first, but the trick is in the detail,” explains Andreas Rosum. “The cooling sheet must be inserted at certain angles to achieve inherent stability. With plate dimensions of sometimes 2 m by 2.50 m or even the smaller sheets of 1.80 m, this is a challenge because I must not compromise my measuring capability during clamping.”

Initially, they considered measuring the sheet in vehicle position, but this approach was discarded, as the measuring system would have been limited in use and the scanning head could not have cleared the plate. They then decided to omit the rotating mechanisms and, after consulting with the automotive customer, to tilt the component for measurement at a defined angle (10 to 15 degrees). “If I have too much material between the plate and the scanning head, I have problems with shadow casting. I then need to scan at many angles. This means that the measurement time is significantly extended. Certain angles can also cause reflections. The idea of clamping the entire frame on one side and doing this with vacuum technology was brilliant,” concluded Andreas Rosum. Benjamin Ostrowski explains: “For this project, we had to bring in all our expertise in vacuum technology. But the combination of the bellows suction cups and our powerful vacuum units ultimately allowed us to solve this clamping task to Mubea's satisfaction. The bellows suction cups serve as a support surface for the workpiece to be clamped, as they are particularly stable and precise, ensuring the reliable use of the clamping system. Through the continuous development of new technologies and our tool and equipment manufacturing, we are independent and able to respond very flexibly to our customers' individual requests.”

Vacuum Technology Opens New Possibilities

For the cooling plates, both the flatness of the bonded aluminum plates and the channel layout had to be measured. The channel layout has many features. “Thanks to the vacuum technology solution, we now only need two bridges to apply the reference points,” summarizes Markus Brüggemann. “WITTE has opened up new possibilities for us with its uncomplicated and innovative solution competence.” Andreas Rosum adds: “Mr. Ostrowski is no stranger to our company. This makes the collaboration quite harmonious. When we had optimization suggestions or inquiries, the processing was always very quick. Project management at WITTE was always involved and in communication with our technicians. There was once, if I remember correctly, a problem with the vibration of the vacuum pump. But overall, such smaller issues were quickly resolved by project management. We never received a standard or generic response, but always very innovative suggestions. This is particularly important for such a new project or product.”

Innovative Through Cooperation

This example shows that electromobility can only really gain momentum when suppliers, like the specialist for innovative lightweight solutions Muhr und Bender KG (Mubea) and pioneering providers in the field of clamping and positioning technology like WITTE, work together as a team to find innovative and creative solutions. Many new products, services, and business models for electric mobility cannot be implemented by a single company alone. Building up the necessary capacities, resources, and expertise is often difficult, time-consuming, and risky.

A partnership, in which specialists contribute their expertise to the collaboration, provides relief.