Measuring Paint Thickness on Plastic Bumpers/Fascias with Advanced Driver Assistance Systems (ADAS)

DeFelsko's PosiTector 200 coating thickness gage is ideal for non-destructively measuring the thickness of paint ("topcoat") applied to plastic vehicle bumpers/fascias with or without Advanced Driver Assistance Systems (ADAS).

For over 25 years, automobile manufacturers and collision repair shops have been utilizing the PosiTector 200 to measure the thickness of paint applied to interior and exterior plastic parts. While the instrument provided assurance that specifications were met, safety had not been the motivation – until now.

With the rapid growth of Advanced Driver Assistance Systems, the ability to accurately measure paint thickness on automotive bumpers and fascias has become imperative. Applying topcoat thicknesses outside of manufacturers' specifications may negatively impact the ADAS sensors' ability to perform properly, reducing overall occupant safety.

This article discusses the importance of accurate paint measurement to meet new bumper/fascia refinishing requirements using the PosiTector 200 by DeFelsko.

Background

Automobile manufacturers continue to incorporate advanced technologies in an effort to improve the overall comfort and safety of vehicle occupants. The inclusion of integrated Advanced Driver Assistance Systems (ADAS) are becoming standard on many new vehicles. Such systems include:

• Blind Spot Detection
• Lane Departure Warning Systems
• Pedestrian Detection
• Integrated Brake Assist
• Adaptive Cruise Control
• Collision-Avoidance Braking Systems

By 2022, collision-avoidance braking systems will be standard equipment on all vehicles. This is due to a voluntary agreement reached between twenty of the largest automakers, the National Highway Traffic Safety Administration, and the Insurance Institute for Highway Safety. This represents roughly 99 percent of the United States auto market. Similar agreements have been established in the European and Indian markets.

These Advanced Driver Assistance Systems often utilize sensors that are integrated into vehicles' bumpers and fascias to detect motion and proximity to objects. There are limitations on their ability to work properly when their signal strength is impeded by repair work or excessively applied paint. For this reason, automotive manufacturers such as General Motors have limited ADAS equipped bumper/fascia repair work to paint refinishing. The paint thickness must not exceed the OEM manufacturer's recommendations; for example, General Motors states that paint thickness on ADAS-equipped bumpers/fascias must not exceed 13 mils (330 microns). Excessively thick paint will negatively impact the sensors' ability to function.

It is now more critical than ever for manufacturers and collision repair shops to accurately measure and control paint thickness during the refinishing process.

DeFelsko's Solution

The PosiTector 200 B ultrasonic coating thickness gage is ideal for measuring paint thickness on automotive plastic bumpers, fascias and other exterior and interior parts. It is ready to measure out-of-box with no calibration adjustment required for most applications.

Two models:

• The PosiTector 200 B1 (Standard model) is the economical and most common solution for measuring the TOTAL coating thickness.
• The PosiTector 200 B3 (Advanced model) is capable of measuring both TOTAL coating thickness AND up to 3 individual layer thickness in a multi-layer systems.

How it Works: The PosiTector 200 B probe emits a high frequency sound pulse that travels into the coating via a coupling gel and reflects from ANY surface that is different in density. Coating thickness readings are obtained by measuring the time taken for the ultrasonic signal to propagate from the probe tip to the coating/substrate interface and back. The travel time is divided by two and multiplied by the velocity of sound in the coating to obtain the thickness of the coating.

By default, the PosiTector 200 interprets the largest "echo" within the selected range as the coating/coating or coating/substrate echo.

Automotive coatings are characteristically multilayer systems consisting of an adhesion promoter, primer, basecoat and clear coat layers. This application note focuses on measuring the total combined thickness of the paint system over plastic bumpers and fascias. For information on multi-layer automotive paint measurement see our Ultrasonic Paint Thickness Measurement - Plastic Substrates application note. Specifically, the section "Application #4 Measuring the Individual Layer Thicknesses in a Multi-layer Application".

How to Measure

The PosiTector 200 B is ready to measure automotive paint thickness out-of-box with no adjustment required. For best results measuring the overall total coating thickness applied to bumpers/fascias, we recommend enabling Max Thick Mode within the Setup menu. Once enabled, follow these simple steps.

Squeeze a droplet of ultrasonic gel (couplant) onto the coated bumper or fascia.

Place the probe onto the gel and press down to initiate a measurement.

Lift the probe when a double beep is heard and the measurement is displayed. A second reading may be taken at the same spot by continuing to hold the probe down on the surface.

The displayed measurement indicates the total thickness of the paint system. The following images are examples of the PosiTector 200 B Standard and Advanced measurement screens in Max Thick Mode.

In the above example (right), Layer 1 is 2.0 mils thick. Layer 2 is 1.4 mils thick. Total thickness is 3.4 mils. The graphical display shows two "peaks" representing two distinct material interfaces. Although the coating system is actually comprised of 4 layers, the instrument combines the thicknesses of the first 3 layers (adhesion promoter, primer, base coats) into one value of 1.4 mils. The final top clear coat is measured individually as 2.0 mils. The total coating system thickness is 3.4 mils. For more information on the Graphics mode and measuring multiple layers click here.

Note: The PosiTector 200 B can also display measurement values in micron units (metric).

When finished measuring, wipe the probe and the surface clean with a tissue or soft cloth. It's that easy.

Conclusion

As automobile manufacturers continue to add more monitoring systems to their vehicles, the need to accurately measure the coating thickness applied to plastic auto bumpers/fascias with integrated sensors is becoming imperative. The PosiTector 200 B by DeFelsko is the simple, durable, and accurate way to perform nondestructive measurements of coatings applied to plastic car bumpers integrated with Advanced Driver Assistance Systems (ADAS) sensors.