Automotive manufacturers recognize that consumers are quickly shifting their views towards greener transportation. This is driving newer or improved manufacturing processes to produce electric vehicles (EVs). As interest ramps up in creating efficient EVs, the decline of the internal combustion (IC) engine is inevitable.

As the IC engine is phased out, the number of necessary drive train components will dramatically decrease. The remaining parts continue to become more critical to the vehicle’s efficiency and operation, including the transmission components that convert the high torque from electric motors to RPMs at the wheel.

Driving long distances, comparable to IC engines, without stopping to charge is critical to making EVs viable. EV gears have a vital role to play in increased range. To achieve this, they must have a reduced surface texture, ultimately reducing surface friction while maintaining some level of lubricity. In addition, unlike IC engines that mask the drivetrain’s noise, EVs are quiet. The key is to produce the essential gear surface texture and waviness specifications to improve gear tooth interaction while reducing contingent noise.

Role of Precision Metrology

Precision metrology helps to ensure that the process of producing these gears is optimized. The high value of these processed gears nods to a preference for non-contact measuring technologies. Because of the gear geometries and smoother surfaces, tactile technologies can become more challenging to use. They are not able to reach the critical inspection areas or may result in surface scoring. Therefore, key automotive OEMs rely more on 3D non-contact optical profiler solutions.

Within the realm of non-contact metrology, more and more EV parts are being measured by coherence scanning interferometry (CSI). This technology uses specialized optical microscope objectives that provide the imaging and magnifying a surface and measure its 3D topography. CSI-based systems, such as ZYGO’s Nexview, are characterized by extreme stability of the measurement, ease of gaining access to the measurement area, as well as the assortment of objectives to meet the demanding requirements for on-the-floor production metrology.

Field stitching is a capability also advantageous in EV gear metrology. The instrument user can create a matrix of overlapping measurements which can be stitched together to form a larger measurement than a single objective can accomplish. For EV gears, this means the ability to measure surface texture along a gear flank — from edge to edge — or from the gear root to the tip.  ZYGO’s proprietary stitching algorithms can perform these stitched measurements over non-planar surfaces, such as teeth on hypoid gears, allowing a user to re-measure with continuous high precision.

Looking ahead

The growth of the EV market is inevitable. It places significant challenges in front of manufacturers as they wrestle with the need for technological advancements. Top of the list is the requirement for advanced finishing and grinding technologies to produce complex and precise surface features in gear teeth to enhance efficiency and reduce noise, thereby improving customer satisfaction.

Optical metrology is a versatile inspection method and has an essential role in verifying gear quality and design intent achievement. Today, it has become the "go-to" metrology solution, benefiting from the fact that it is non-contact, non-destructive, fast, highly sensitive, and has exceptional resolution and accuracy.