The technicians conducting scanning, sensor or camera replacements, reprogramming and calibrations are well aware of the challenges ADAS brings to collision repair. But the technology is having impacts in the refinish department as well.
During a panel discussion at a recent industry event, paint company representatives were asked about some not uncommon practices in shop paint departments. Some painters, for example, will sometimes use leftover paint from another job as a ground coat on a vehicle with a similar color. But ADAS has the paint manufacturers even more vehemently warning against this shortcut practice. Radar sensors located behind bumpers, for example, can be impacted by anything in between the sensor and what it is detecting---and that includes the metallic coatings being sprayed in body shops.
“It’s not all metallics, and it’s not all metallics [affecting the ADAS] in the same way,” Jeff Wildman of BASF said. “Certain sizes and shapes impact differently.”
That makes following the “radar-approved” formulas for products being sprayed in the areas over sensors critical. “When you look up a color, we’re going to tell you if you need a tinted undercoat,” Wildman said. “A tinted undercoat is not the leftover silver you have. It’s following the procedures for how you match this color. In a lot of cases, that tinted undercoat is required because we have a transparent color. To get the color match, you actually have to see through the basecoat to the tinted undercoat.”
It also means painters shouldn’t “put on six coats to get coverage because they didn’t use the right undercoat,” Wildman said, because the mil thickness over the sensors can impact their performance as well.
“It’s just like if you look at any OEM repair procedure and it tells you no body filler over the radar units,” he said. “It’s the same type of thing. Any material that goes over that is going to have some impact on that radar transmission. It’s just a matter of how much.”
“I don’t think there’s such a thing as a ‘cosmetic repair’ of a bumper anymore,” Gary Kilby of Sherwin-Williams said of ADAS-equipped vehicles. “It has to include consideration of the metallic content, whether the bumper has been previously painted, how many mils of basecoat are you going to put on it. You have to make sure you’re [measuring the mils of material on] the bumpers before you repair them, and after.”
The paint companies also are cautioning against another “work-around” practice some paint shops do when mil thickness on a repainted bumper cover is too high: grinding or sanding down the back side of the cover.
“You no longer have a totally flat, level surface, and that’s going to impact the radar" behind that bumper, Wildman said. “Because now you have different thicknesses of material in different areas right over that radar unit that potentially can impact how that transmission goes out. It could deflect the radar to the right or left.”
Tracy Frye, a technical consultant with AkzoNobel, said this is also why it’s important not to blend over an area with a radar sensor behind it. “That can cause the radar to give a scattered effect,” he said. “Everything needs to be uniform over that area.”
The paint companies also say the formulas for the colors sprayed on those parts have been specially approved and can’t be altered.
“It’s called a radar variant, and we flag it that way in our color information system,” Wildman said, noting that for a particular color, a waterborne formula may be approved, for example, when the solvent version isn’t. “It’s the only color that’s approved for use over a radar sensor in repainting a bumper.”
“That means you can’t go tinting the formula,” Kilby concurred. “You can’t say, ‘I want to bring this color in a little bit closer’ because if a painter tries to tint it, now the formula is no longer radar-approved. To be straightforward, color match may have to sacrifice a little bit to make sure that formula is radar-approved.”
That may mean additional steps if the color match isn’t there. “Unfortunately, there’s going to be more blending” onto adjacent areas, Kilby said. “We know the challenges of getting insurance companies to pay to blend for bumpers, but in this case, it may have to be a blend because of the radar. If you have a color formulation that’s not blendable, we would contact the color lab. Maybe we send a panel in overnight and try to dial that color in a little bit closer. It could be a variant out there that we just haven’t found yet. But you can’t tint these radar-approved ones.”
All these new challenges add to the importance of including paint considerations early in the process, during repair planning.
“Understand what you need to do before you get that car in the booth on Friday morning and are planning to deliver it that afternoon,” Wildman said. “Typically, painters have not had to look at repair procedures. Working with painters, they don’t know how to do that today. ‘It’s a simple bumper repair. Get it in, get it painted and get it back on the car.’ That’s the way some shops and painters look at it. We’ve got to change that mentality. Because the painter and shop need to understand what’s behind that bumper. It’s really got to be driven from the front office as part of the repair plan.”
In addition to following paint manufacturer guidelines for painting bumper covers over radar sensors, shops should also be aware of the growing number of vehicles requiring a radar power test after post refinishing and after the system is calibrated.
“It’s a static function test to see if painting a bumper has reduced the power of a radar sensor too much,” said Nick Dominato, director of product management for I-CAR.
The test is needed if the system uses higher resolution radar for blind spot systems able to identify not just a vehicle in the blind spot but even smaller objects such as a bicycle. The test uses “essentially a metal pole on wheels,” Dominato said, to measure when the system is engaged how much the bumper cover is reducing the power signal of the radar sensor.
“If it’s within a certain band, you’re good to go,” but if it’s beyond that, you may have to scrap the bumper cover if repainting is not allowed by the automaker, Dominato said.
The test is currently required for some Mercedes-Benz and Toyota vehicles. “I think we’re going to see a lot more of these radar power tests in the future,” he said.
John Yoswick