Under the Skin: How the Automotive Painting Process Goes Green

Over the past year, new precision painting processes have emerged that promise to speed up car manufacturing, make them more durable, and allow automakers to offer a wider range of color options and decorative finishes.

Earlier this year, Under the Skin looked at ABB’s new robotic Pixelpaint, a technology that applies paint in the same way as an inkjet printer, creating sharp edges on the paint rather than the slight haze associated with conventional spray guns. It also means that there is no overspray and the company claims that 100% of the paint is applied to the car. On the other hand, about 20% of the paint applied by conventional techniques ends up in the filters of the spray booth. The German company Dürr has a similar technology called Ecopaintjet being tested by BMW and the process is already in use at Audi.

Traditionally, painting a car has been one of the dirtiest and most wasteful parts of the production process. In the past, paint from high-pressure spray guns would bounce off the surface of the car body, creating a mist of paint droplets that were sucked out of the spray booth by fans and filtered. Next are the HVLP (high volume, low pressure) guns, which are a huge improvement. But any two-color process (like different-colored roof panels) still involves the tedious process of applying and drying the first color, masking it with tape and paper to protect it from splatter, and then painting it. apply the second color.

The new robot systems are quite different. The Pixelpaint spray head is equipped with 1000 nozzles that shoot tiny droplets of paint, the smallest of which is about the size of two human blood cells, giving very sharp edges to the paint when it is applied. The Ecopaintjet robot is similar, applying paint through a perforated nozzle plate with 50 small holes at a distance of 30mm. Prior to any paint job, a measuring system makes paintless passes over the hull, determining its precise shape so the robot can follow its path evenly across the surface. The software uses this data to calculate the paths the applicator should take as it travels over the body surface, simultaneously controlling the speed and tilt angle of the spray head.

Once done, the robot can start painting, covering around 1.8 square meters per minute and taking around two minutes to complete a typical car roof panel. To do the job the traditional way by removing the body from the paint line, Dürr estimates that masking and applying the second color would take several people 50 minutes. The new method also saves around 15 square meters of masking tape and film per body shop. Additionally, the new technique is estimated to save up to 25% energy during the paint drying process.