From automobiles to bikes, electric vehicles (EVs) are gaining momentum and consumer demand. Moreover, the U.S. government has set a goal to make half of all new passenger cars and trucks sold in the country zero-emissions vehicles by 2030 and to build a network of 500,000 chargers to help make EVs accessible to all Americans for both local and long-distance trips.
Some key new components for EVs include motor housings, battery trays, end covers, stators/ rotors, gear cases, gears, and regenerative braking. These parts need to be lighter than their internal combustion engine (ICE) powered counterparts. So it follows that housings, cases, and covers for an EV powertrain tend to be aluminum. New materials are also constantly being researched and developed to further reduce weight and increase durability. Such materials can be challenging for existing tool geometries, so new tooling needs to be developed to effectively machine future materials.
The electric motor is obviously the biggest difference between EVs and traditional ICE models. The challenge is to produce them as light as possible, while maintaining durability. As a result, new tooling geometries and materials are being created to meet stringent performance specifications and demands for more efficient power-generating units with a long life.
Gears are an integral part in EVs and require tight tolerances to reduce the noise they generate. Due to the various types of gears, different machining processes will be required and new technologies need to be developed for efficient gear machining.
Even though fewer parts are needed to produce an EV, the parts for electric drives are more complex, smaller, and may have more filigree. To meet the growing EV demand, tooling considerations for part manufacturers include selecting the right high-performance taps and high-precision clamping solutions.
Unlike their combustion engine equivalents that have utilized cut taps for cast iron chip-machining applications, EV threads can utilize thread forming tooling. Due to minimizing component size and material weight requirements, EV applications require internal threads that reach the bottom of a hole within a pitch. Cold-forming taps for the chip-less production of internal threads are an excellent option for achieving higher tolerance threads.
The essential advantages of cold-forming threads are excellent surface quality, as well as higher static and dynamic strength of the thread. The length of the thread to be produced is not limited by chips, which must be removed. The tools have excellent stability, especially with small thread sizes. For example, when threading 32 holes in an aluminum floor battery case for an electric car, an Emuge cold-forming tap in an Emuge SpeedSynchro modular tap holder increased productivity, reduced cycle time by more than 30 percent, and increased tool life while utilizing a stable process.
Electric vehicle components can also create new milling challenges and opportunities. Components such as rotor shafts, CV joints, scroll compressor components, and ball screws require high surface finish and part quality but can be challenging to machine effectively and efficiently while maximizing machining times. Emuge-Franken has developed specialized tooling for gear skivving that has consistently provided high process reliability, up to 70 percent time savings and 50 percent cost savings. In CV joint machining, Emuge-Franken has also developed specialized tooling resulting in high process reliability within extremely tight tolerances, generating time savings as much as 30 percent.
The biggest challenges for clamping EV parts such as the gearbox, rotor, and stator, are the material and the weight. Because less material is used to reduce weight, there is a possibility of destroying the parts on the clamping units.
In a successful application for clamping an electric car rotor for turning and milling, the rotor was clamped over two levels—square and cylindrical. First, the clamping was done with a classic clamping bush. Then a second, square clamping surface was created via wedge jaws. The end stop was located between the two clamping plans, which ensured radial compensation. Benefits of this design include a clamping bush and end stop that can be exchanged, enabling use over several machining processes. Also, the design of the clamping device offers sufficient space for taking measurements with a probe.
In an electric bicycle, the drive components—including the electric motor and battery—are comprised of an extremely thin-walled and lightweight material with a complex geometry designed to meet tight manufacturing tolerances and fit into a bike’s confined spaces. It can be challenging to clamp thin-wall aluminum during a machining operation. Too much clamping pressure can cause the workpiece to distort, whereas not enough pressure may cause it to slip. While slippage is unacceptable, distortion is even worse in precision machining. The workpiece may at first seem acceptable, but when inspected, the distortion from the force of clamping the workpiece can be detected. In some cases the inspection data will define the exact location the workpiece is being clamped, simply due to the excessive distortion in the location that the clamping device was engaged with the workpiece. Emuge recommends using a finite element method (FEM) calculation, which is helpful to investigate strength and deformation, and to simulate the possible stress forces and their effect on a component.
Emuge-Franken offers clamping tools for E-bikes and pedelec (low-powered electric bicycles) applications, such as drive shafts. A recent single clamping solution featured three jaws that gripped the workpiece at three defined points via a two-stage approach of the clamping jaws. Emuge-Franken found that the entire process resulted in minimal deformation and had a holding torque of 5 Nm during grinding.
EVs are becoming mainstream, offering a new realm of possibilities for our lifestyles, and manufacturers need to keep pace with new tools and strategies. Emuge-Franken is well positioned to meet these challenges.
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