Ensure a Dimensionally-Correct Windshield

By Ken Pew

Advanced Driver Assistance Systems—more commonly known as ADAS—has become the blanket term to describe the equipment and sensors installed and programmed into a vehicle for assisting drivers with appropriate traffic warnings and, in some cases, they provide actual position adjustments to reduce accidents.

Originally introduced on high-end vehicles, the obvious advantages ADAS features provide have resulted in many automakers, including Ford Motor Company, making them standard features on their vehicles. As these systems become more prolific, their role in completing an approved, proper and safe vehicle repair will continue to grow as well. This will require an awareness of the importance of using OEM replacement glass when one or more of these features inter-faces directly with the glass components. Cameras, which may be mounted directly to the windshield or positioned looking through it, are the most common feature.

These cameras—combined with a radar sensor within the vehicle’s body panels and front grille—communicate with each other to create a “force field” around the vehicle. These embedded sensors warn drivers of potential accidents.

It’s important to know that all sensors are turned on and then “zeroed” to the center of the vehicle during the assembly process, meaning the entire exterior shape of the vehicle—including the glass surface’s unique curvature—is crucial in order for the radars, cameras and sensors to “know” where they are in relation to the vehicle exterior. Projecting out from the vehicle, these sensors provide feedback to the onboard software, which communicates with the driver in various ways, starting with an audible alert, and escalating all the way to taking control of the vehicle.

This is important because, while windshields have long been considered a structural part of the vehicle, now more than ever, their dimensional repeatability for both assembly and service is critical to ensure ADAS features operate as intended.

Many glass engineers, already armed with this knowledge, recommend the need for calibration of the cameras after the windshield has been replaced. This process—when completed with OEM glass—will properly reset the new position of the camera as it relates to the “force field” around the car. The vehicle software needs to “know” the new position of the camera; if it is too far away, feedback to the on-board software may not be correct.

In today’s windshield manufacturing process, automakers demand entire surface control and have upwards of 30 to 50 embedded sensors in the final check gauge, with each point rated within +/- 3 sigma of nominal measurement. This provides the confidence that during OEM assembly, the vehicle-to-vehicle variation is kept accurate and repeatable, so there are no interruptions in process flow, while at the same time providing confidence there will be no problems with the initial end-of-line calibration setup.

When installing a new wind-shield, technicians must under-stand that not only is its correct placement important—from side-to-side and up-and-down—but the curvature over the entire surface also plays a large role in correct operation and providing accurate feedback to the driver. Technicians should also be careful to avoid any optical distortion from entering the camera zones.

Once the windshield service has been completed properly with the right glass and all calibrations finished, the ADAS features and other benefits should work as intended.

Being well-versed in these and other windshield-related ADAS issues—while making sure to fol-low all OEM repair procedures—is critically important for repairers to help ensure they deliver a properly repaired vehicle to their customers.

EDITOR’S NOTE: Ken Pew is FCSD/Carlex technical services manager. This article is reprinted with permission from Ford’s On Target magazine, Volume 3 2018. The opinions expressed by guest columnists are their own and not necessarily those of AGRR magazine.

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