The passenger car brake disk of the future is resistant to wear, resistant to corrosion and does not produce any fine dust – this is made possible by a hard metal coating that is applied to the disk by a laser welding process. The corresponding holistic machine solution is developed by EMAG LaserTec. A conversation with Dr. Andreas Mootz, managing director of EMAG LaserTec, about the benefits of laser metal deposition and the corresponding new machine, ELC 450 LMD.
Mr. Mootz, why are automobile manufacturers currently developing coated brake disks?
There are two main reasons. On the one hand, a great deal of fine dust is produced by conventional brake systems – a topic that has been attracting more and more attention for a while now. On the other hand, the increasing significance of e-mobility plays a role, due to the fact that the brakes of e-cars are rarely used. This is because there is already a sufficient braking effect during the recuperation of the engine. However, brake disks that not used for long periods may under certain circumstances begin to rust. This is why the brake disk technology is currently undergoing a change. For example, hard-coated brake disks are increasingly being used, as they are virtually resistant to wear and corrosion. Furthermore, they produce no fine dust.
How are these disks coated?
Currently, high velocity oxygen fuel spraying (HVOF) is frequently used. With this method, the coating is shot onto the component at high speed. However, this whole procedure involves high material losses. This is one of the main reasons why we at EMAG LaserTec have been working on an alternative in recent years – laser metal deposition. With this method, a bond layer and the hard metal layer on top of it are applied to the brake disk by a laser welding process. So almost no material is lost.
How reliable is this method?
From the very beginning, our machine development was focused on process reliability. This factor is, of course, indispensable to mass automobile production and we now have the perfect solution ready: the new ELC 450 LMD machine. It contains a turntable with five stations, which each component passes through a total of four times – twice per side as the coating consists of two layers.
What happens at these five stations?
In the first station, the component is weighed uncoated. This value is used as a reference to be able to determine the coating weight later, when the component is weighed for a second time after one pass. In the second station, any work materials and dirt are then removed from the blank by means of laser cleaning. In the third station, induction technology from EMAG eldec ensures an ideal processing temperature. The actual laser coating procedure is then performed in the fourth station. The entire process benefits from the sophisticated design of the laser tool, in which the material powder is fed in through a channel. The material fuses with the disk surface at the melting point of the welding process. As last step, the component is measured and, after two coating passes, is flipped over to coat the second side. Then the described process starts from the beginning again. Finally – after a total of four cycles – the component is unloaded. This combination of high-precision laser coating technology with cleaning and pre-heating processes as well as quality assurance measures, such as weighing, ensures the necessary process reliability.
What role do the upstream and downstream production processes play for the component?
The disk blank is turned beforehand, and a grinding process is necessary after the coating process – both processes can be implemented with EMAG technology. This is where our strength comes into play. At the customer’s request, we provide the complete production solution for the next generation of brake disks from a single source. With our wealth of process expertise, we stand for holistic solutions in numerous areas of application. This will soon also include coated brake disks.
The last question is about where you are right now. Is the development of the machine complete?
The development of the machine with its five stations and the corresponding processes is complete. However, we are currently still conducting tests concerning the coating and the coating process. But there is no doubt that we will be able to offer our customers an extremely efficient solution in the future.