With the introduction of the EURO 7 standard, braking systems in cars will have to undergo massive changes, as this is the first time that particulate emissions have been regulated and many current models do not meet these requirements with their brakes. What does this mean in concrete terms for automotive production, what role does the hard coating of brake discs play and why is EMAG’s new laser metal deposition technology the ideal solution? An interview with Dominic Grimminger, brake disc coating expert at EMAG.
Why is the topic of “brake disc coating” so important?

Dominic Grimminger, specialist at EMAG for the machining of brake discs.
This is mainly due to the EURO 7 standard. For the first time, not only exhaust emissions from the combustion engine are regulated, but also particulate emissions from tires and brakes. For the latter, a value of only 7 milligrams of particulate matter per kilometer will then apply – and that for all models. By way of comparison, this value is currently between 5 and 40 milligrams, depending on the model. A way must, therefore, be found to massively reduce emissions, especially for larger vehicles with higher particulate emissions. This is possible with hard coating of brake discs in combination with a brake pad matched to them. No design changes to the vehicle are necessary.
Are there alternatives to reduce particulate emissions from the braking system?
The media often mention extraction systems that are located near the brakes and, thus, absorb the fine dust. However, only some of the emissions are extracted in this way. In addition, manufacturers would have to plan for additional installation space, accept higher unsprung masses and make major design changes to the vehicle, which increases the overall cost enormously. Another option is the use of so-called NAO (non-asbestos organic) brake pads. This actually reduces particulate emissions. However, this only applies to brand-new brake discs. After a short time in use, they rise again to their current level.
What challenges are there when coating the panes?
In principle, the idea of coating brake discs is not new. However, the production costs are often too high and the process based on thermal spraying or electroplating is too complicated. Complex pre-processing is required to bond the coating. In addition, the layers are (too) thick and the heat input is high. In this context, a new development from EMAG in the field of laser cladding of brake discs represents a major advance for this task. The new production solution is economical, suitable for large-scale production, reliable and variable, as a variety of material combinations can be used.

Laser cladding is used to apply a two-layer coating that protects brake discs from corrosion and wear.
What distinguishes this solution in detail?
The focus is on the well-known laser metal deposition technology. Material powder is fed into a laser tool through a channel. It then fuses with the surface of the disc at the melting point of the welding process. EMAG has optimized this approach with its laser coating technology. The process ensures that the area rate is always very high, the coating thickness is minimal and the surfaces are particularly smooth – and all this with low roughness. Just two figures to illustrate this: the EMAG laser coating process achieves surface application rates of 2500 cm²/min, which is many times higher than with conventional laser cladding. And while the layer thickness in conventional laser cladding is typically around 0.5 mm, we achieve values of up to less than 0.01 mm here. On this basis, the process is suitable for large-scale production.

Structure of the laser tool: The coating material is fed in as a powder and fused to the component surface using a laser process.
What role does mechanical engineering play?
With its extensive process expertise in laser machining and double-sided face-grinding – both processes play a role here – EMAG ensures that users receive turnkey solutions for the entire process chain on request. For example, there is already a sophisticated machine concept for laser cladding of brake discs with three rotary tables in one machine. The base layer is applied on the first one, which is approximately twice as fast as applying the hard material layer above it in parallel on two components on the two subsequent rotary tables.
The EMAG solution for double-sided face-grinding of the hard coating of brake discs benefits from high rigidity and an intelligent cover concept on the grinding wheels. Both grinding spindles are arranged in parallel, with the brake disc being machined by cross grinding. The grinding wheels sharpen themselves.

The ELC 450 DUO LMD with two process modules enables increased productivity in the hard coating of brake discs.
How variable is the entire solution?
Almost all variants can be covered, both in terms of mechanical engineering and the required coatings. On request, we even provide support in the design and development of coating systems, although existing coating concepts can of course also be implemented. Overall, customers benefit from our comprehensive know-how – from the question of laser power and the corresponding nozzle concepts to parameter optimization. On the other hand, EMAG can flexibly adapt its machine concepts. For example, integrate only two rotary tables into the machine for single-layer coating. In summary, this means that the whole system stands for extensive process expertise and comprehensive solutions from a single source.