Manufacturing rotor shafts at the speed of light with laser welding

How does EMAG LaserTec use its flagship ELC 6 system to accelerate the production of critical powertrain components?

EMAG LaserTec has sponsored this post.

The surging popularity of electric vehicles worldwide means production planners need to hit the gas on the manufacturing of essential e-motor parts. One key component is the rotor shaft, which converts electrical energy into kinetic energy and transmits it to the drivetrain. Unlike a combustion engine’s crankshaft, the rotor shaft needs to handle significantly higher speeds (20,000 rpm versus the crankshaft 3,500 rpm). It must, therefore, be manufactured with tight tolerances, as even minimal imbalances can impact the motor’s lifespan.

While rotor shafts have traditionally been solid, there are certain advantages to manufacturing them in two pieces. For one, a hollow design would allow for internal cooling channels to be incorporated, leading to improved thermal management and a more efficient motor. Moving from solid pieces to assembled rotor shafts offers further benefits such as lower raw material costs due to more lightweight parts.

Furthermore, changes in the rotor shaft design to different demands can be realized easier, as the adaption of the single components is easier.

“You have a lot more freedom to design,” added Konrad Eibl, head of Offer Engineering at Germany-based EMAG LaserTec. “For example, you can design internal geometries on the single components, which cannot be machined in a solid part.”

Assembled rotor shafts offer more design freedom. (Image: EMAG LaserTec.)

Laser welding plays a central role in “building” these two-piece rotor shafts. EMAG’s ELC 6 machine is one prime example of a highly precise production laser welding system — and it is capable of producing as many as 500,000 rotors per year.

A look at the ELC 6

One key feature of the ELC 6 is its rotary indexing system that enables parallel processes through simultaneous load/unload and machining. That means that while one part is being welded, the other side of the swivel table can be loaded and unloaded, reducing cycle times and enabling the high-volume production of powertrain components with circumferential welds.

“Maybe that’s the speciality of German engineering — we try to do everything inside one machine,” said Eibl. “However, you have to pay attention to the required cycle time, of course. The highest investment is usually in the laser welding, so it should be the “slowest” part of the system, meaning this part should never wait on other processes. So, the goal is to design a system with parallel processes to achieve the best efficiency”

The ELC 6 specializes in the high-volume production of rotor shafts. (Image: EMAG LaserTec.)

The ELC 6’s laser welding process typically begins with a gantry that transfers individual rotor shaft parts onto the swivel table. EMAG’s LC 4 laser cleaning machine, which can be interlinked with the ELC 6, removes dirt, meaning organic substances, using pulsed laser radiation. The components are joined on a spindle and induction preheated to an ideal processing temperature.

EMAG’s EC Seam system then uses the triangulation method to precisely scan the contours of the weld seam, and readjusts the position of the weld head as needed. The system works by projecting a laser line across the weld seam and using a camera in the weld head to take up to 20 measurements around the circumference of the part. EMAG’s proprietary EC Seam software performs seam position control, and the weld head proceeds to follow the 20 points during welding. The vertically aligned workpiece rotates while the laser optics remain stationary, only making slight vertical adjustmentsrelative to the workpiece. A pyrometer continuously monitors the temperature throughout the welding process.

Laser welding in the ELC 6. (Image: EMAG LaserTec.)

“Using the right tooling is important to have that precisely metered, concentrated energy of the laser beam,” said Eibl. “For one, you focus all that energy with the best possible efficiency onto the workpiece. At the same time, you don’t want to lose that heat and distribute it inside the workpiece, as it will lead to deformation.”

Once welding is complete, the assembled rotor shaft is transported out of the ELC 6, while new components enter the machine.

EMAG’s automation difference

So, what distinguishes EMAG’s ELC 6 from other laser welding machines? For one, there is the weld head’s NC positioning unit.

“The NC, or numeric controlled, positioning unit for the weld head gives the machine added flexibility because it can be moved vertically, horizontally and it can also swivel,” said Eibl. “So, you could use that to produce flexibly without manual changeover for different workpieces. You can weld one workpiece from the side, then change over automatically and weld the next workpiece from the top. You can weld at an angle. You can also do special applications like interpolation—meaning during the process, change the angle if the workpiece requires it. We do that, for example, on elliptic parts.”

When it comes to retooling, there are several advantages to prioritizing automatic changeovers over manual ones. Since manually swapping tooling can lead to laser misalignment, the first part of a new batch always has to be sacrificed for inspection. The ensuing cutting, polishing, etching, and microscopic analysis can add up to an hour of downtime. Automatic changeovers eliminate this need, saving significant time and material waste.

Another benefit of the ELC 6 is its “best-in-class accessibility for maintenance activities,” according to Eibl.

“When you go to the ELC 6 machine, open up the front door and take a step forward,” explained Eibl, “you are literally standing inside the machine, and right in front of you is all the relevant process equipment.”

There are a number of factors that set EMAG’s laser welding systems apart in general. Automation is a big one; after all, just a decade ago the company was called EMAG Automation. Since then, the laser welding has become the core business, but the experience as an automation company still helps tremendously.

EMAG’s production line ranges from robots and loading gantries, to pallet conveyors, stacker cells and EMAG’s own TrackMotion system. Eibl argues that the focus should be on keeping things simple and cost-effective when designing systems tailored to customer needs. For example, he recommends using gantry loaders instead of six-axis robots for transporting raw parts from the conveyor to the laser cleaning machine, as the robots’ flexibility is not needed in this case and the gantry loaders can save space and reduce costs.

Eibl advocates that the best approach to laser welding is to steer away from larger dial table machines and opt for a fast and flexible welding machine instead.

“If you need to add complexity to make the process faster, do it in the automation,” said Eibl. “Our approach is to keep the laser welding to one machine and then build other stations alongside it. It’s just easier to have that step by step.”

EMAG: A one-stop shop

EMAG offers a comprehensive range of technologies for manufacturing systems, handling processes from raw forged parts to completely finished grinded parts. Functioning as a single-source provider allows the company to maintain control over many aspects of the system — from developing their own gantries, to software programming and maintenance. This, in turn, ensures compatibility between different stages of production.

“Getting all of the sub-processes, like laser cleaning, brushing, ultrasonic testing, truly out of one hand — there, I think we are definitely unique,” said Eibl. “I think no one else on the market is able to deliver this many processes truly out of one hand.”

The centralized approach also minimizes production downtime, as customers can reach out to a single point of contact if they run into any issues.

In most cases, EMAG’s process chain starts with the sales team working closely with project engineers to develop most of the concept system during the quotation phase. Once business is awarded to EMAG, the design team takes over, with mechanical and electrical engineers collaborating to bring the system to life. While components are sourced, the software programming team works out automation cycles that will be used within the laser cell.

As all this unfolds, process development can be done concurrently on similar equipment at EMAG’s Laser Application Centers, which EMAG operates in Heubach, Germany; in Taicang, China; and in Farmington Hills, Michigan. Due to close cooperation, the requirements of the local projects can usually be met in the most efficient way.

“While the machine is being built, while everything is in purchasing or in assembly, EMAG’s Laser Application Centers can work on the process in parallel on similar — or even the same — equipment, which is later used for mass production,” said Eibl. “Once the process is completely developed, it can be integrated on the actual production system.”

Upon final assembly, the system is customized to the customer’s workpieces and a run-off is conducted. EMAG delivers and reassembles the system at the customer’s facility, and provides recommissioning support.

In addition to process development, EMAG’s Laser Application Centers offers prototyping with the same tooling used in final production. This eliminates potential issues that can arise when transferring from a prototype on a different machine to the actual production system. The Laser Application Centers can also support limited pre-series production runs, providing parts made with the intended tooling while the main production system is still under construction.

“I don’t think I’m exaggerating when I say for the laser welding of powertrain parts, we have vast experience,” said Eibl. “Our team has the capability of working on complete systems and has an overview from the first process step to the last process step. Having this capability provides the customer the benefit of having a complete process chain planned and proven so critical things are not missed.”

To learn more about the ELC 6 Laser Welding Machine and EMAG LaserTec, visit their website.