Under the skin: how the car painting process goes green

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

Earlier this year, Under the Skin took a look at ABB’s new robotic Pixelpaint, a technology that applies paint much like an inkjet printer, creating sharp edges on the paint rather than the soft blur associated with conventional spray guns. It also means there is no overspray and the company claims 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 paint booths. 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 is one of the dirtiest and most unnecessary 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 which were sucked from the spray booth by fans and filtered. Then came the HVLP (high volume, low pressure) guns, which brought a huge improvement. But any two-color process (like different colored roofing panels) always involves the tedious process of applying and drying the first color, masking it with tape and paper to protect it from splashing, and then l application of the second color.

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

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

BMW is testing the same technology on an in-house fleet of 19 M4 Coupes, applying two-tone paint and M4 logos to the trunk and hood. BMW estimates that if the system is adopted, reducing the energy filtering overspray from the air in the spray booths could save 6,000 MWh of energy over 7,000 hours of operation and reduce the footprint. of its manufacturing processes of 2,000 tonnes of CO2 per year.