Using laser welding technology to manufacture rotor shafts at the speed of light

How can EMAG Laser Technology accelerate the production of critical powertrain components using its flagship product ELC 6 system?
The rapid popularity of electric vehicles worldwide indicates that production planners must increase their efforts in producing key components of electric vehicles, particularly the rotor shaft. The importance of the rotor shaft as the core component for converting electrical energy into kinetic energy and transmitting it to the transmission system is self-evident.

Compared to the crankshaft of an internal combustion engine, the rotor shaft needs to handle higher speeds (up to 20000 revolutions per minute, while the crankshaft only has 3500 revolutions per minute). Therefore, the manufacturing of rotor shafts must follow strict tolerance standards, as even the smallest unbalance can have a significant impact on the service life of the motor.

Traditionally, rotor shafts are solid, but hollow rotor shafts with a two-part design have significant advantages. Firstly, the hollow design allows for the integration of internal cooling channels, thereby optimizing thermal management and improving motor efficiency. In addition, the shift from solid components to assembled rotor shafts also brings other benefits, such as reducing component weight and thus lowering raw material costs.

More importantly, due to the stronger adaptability of individual components, it is easier to adjust the design of the rotor shaft according to different needs. You have more design freedom, "emphasized Konrad Eibl, director of quotation engineering at German company Emark Laser Technology." For example, you can design internal geometric shapes on a single component, which cannot be achieved on solid components.

Laser welding plays a central role in the manufacturing of these two-piece rotor shafts. EMAK's ELC 6 machine is a model of high-precision laser welding systems, with an annual production capacity of up to 500000 rotors.

A notable feature of ELC 6 is its rotational indexing system, which achieves parallel processing by simultaneously implementing loading/unloading and machining. This means that while a component is being welded, the other side of the turntable can be loaded and unloaded simultaneously, significantly reducing cycle time and achieving mass production of circumferential welding of powertrain components.

Perhaps this is a characteristic of German engineering - we try to complete all the work in one machine, "Eibl said." Of course, you must pay attention to the required cycle time. The highest investment is usually in laser welding, so it should be the 'slowest' part of the system, which means that this part should not wait for other processes. Therefore, our goal is to design a system with parallel processes to achieve optimal efficiency.

ELC 6 is dedicated to the mass production of rotor shafts. The laser welding process begins with a gantry, which is responsible for transferring individual rotor shaft components onto the turntable. EMAK's LC 4 laser cleaning machine can be connected to ELC 6 to effectively remove dirt and organic matter using pulsed laser radiation. The component is connected to the spindle and induction preheated to the ideal processing temperature.

Subsequently, Emak's EC Seam system used triangulation to accurately scan the contour of the weld seam and readjusted the position of the welding head as needed. The working principle of this system is to project a laser line onto the weld seam and use the camera in the welding head to perform up to 20 measurements around the circumference of the component. EMAK's proprietary EC Seam software is responsible for executing weld seam position control, and during the welding process, the welded joint will continuously follow these 20 points. When the vertically aligned workpiece rotates, the laser optics remain stationary and only make slight vertical adjustments to the workpiece. Meanwhile, the pyrometer continuously monitors the temperature throughout the entire welding process to ensure the stability and consistency of the welding quality.

Using the right tools is crucial for accurately measuring the concentrated energy of a laser beam, "Eibl emphasized." Firstly, it ensures that you concentrate all energy on the workpiece with optimal efficiency. At the same time, you don't want heat to dissipate and distribute inside the workpiece, as this can cause deformation.

Once the welding is completed, the assembled rotor shaft is transported out of ELC 6, and then new components enter the machine to begin a new round of welding process.

So, what is the unique feature of the EMAG ELC 6 compared to other laser welding machines? Firstly, its welded joints are equipped with CNC positioning units.

The CNC positioning unit of the welding head greatly increases the flexibility of the machine, "Eibl explained," because it can achieve vertical, horizontal movement, and rotation. Therefore, you can flexibly produce various workpieces without manual switching.

You can weld one workpiece from the side and then automatically switch to weld the next workpiece from the top. You can also weld at a certain angle and even complete some special applications, such as interpolation - which means that during the machining process, if the workpiece needs to change the angle, the machine can easily handle it. For example, this is how we operate in the welding of elliptical components.

When it comes to reconfiguration, prioritizing automatic conversion over manual conversion has several significant advantages. Due to the possibility of laser misalignment caused by manual tool replacement, the first part of a new batch always needs to be inspected as a sacrifice. Subsequent cutting, polishing, etching, and microscopic analysis may add an hour of downtime. And automatic conversion eliminates this need, not only saving a lot of time, but also reducing material waste.

Furthermore, according to Eibl, another significant advantage of ELC 6 is its "first-class maintenance activity accessibility".
When you walk up to the ELC 6 machine, open the front door and take a step forward, "Eibl described," you really feel like you're standing inside the machine, with all the related process equipment in front of you.

The reason why Emak's laser welding system is unique is that automation is a key factor. After all, just ten years ago, this company was called Emac Automation. Since then, laser welding has become its core business, but as an automation company, its rich experience still provides tremendous assistance.

EMAG's production line includes robots and loading gantries, pallet conveyors, stacking units, as well as EMAG's own TrackMotion system. When designing systems that meet customer needs, Eibl believes that the focus should be on maintaining simplicity and affordability. For example, he suggests using a gantry loader instead of a six axis robot to transport raw parts from the conveyor belt to the laser cleaning machine, as the flexibility of the robot is not required in this situation, and gantry loaders can save space and reduce costs.

Eibl advocates that the best method for laser welding is to avoid complex large dial machines and choose fast and flexible welding machines.
If you need to increase complexity to make the process faster, then do it in automation, "Eibl suggests." Our approach is to keep laser welding on one machine and then build other workstations next to it. This step-by-step approach is easier to implement and more effective.

Source: OFweek