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The Continuous Efficiency Drive for OEM Painting of Automobiles
Tim December, Expert, Coatings Development, BASF
So, the drive for improved painting efficiency started essentially when the first cars were mass produced. This manufacturing efficiency goal had to be balanced with the customer desire to have a full palette of high-quality colors. This trend continued in the 20th century with the advancement of high tech paint materials and more efficient applicators for high-speed painting.
"The advent of cathodic electro-deposition coatings improved the painting efficiency, met solvent emission requirements and delivered outstanding corrosion resistance to automobiles"
In the early 1970s, the United States EPA solvent emission regulations required the implementation of more efficient waterborne and high solids coatings. The advent of cathodic electro-deposition coatings improved the painting efficiency, met solvent emission requirements and delivered outstanding corrosion resistance to automobiles. The old rusty cars, “rust buckets,” often seen in the midwestern snow and salt are now largely forgotten.
At the beginning of the 21st century, however, many automotive OEM paint shops still followed the basic manufacturing footprint of applying a primer followed by a baking step and then base color coat followed by a clear coat and then another baking step. This was still remarkably like those early days.
The basic layout of the traditional or conventional automotive OEM paint line then is primer followed by a bake; this is most often a 30-minute process oven with a temperature at about 150ºC. After the primer baking step, typically the car body is sent to an inspection deck to look for any painting defects followed by a sanding process to remove defects. After the primer step, the automobile body next is sent to top coat for base color coat plus the clear coat and then the final bake.
The conventional process has in total three of these large baking ovens—each oven is often about 100 meters long using temperatures in the range of 130ºC to 180ºC. Imagine an oven longer than a football field!
The new Integrated Process for high manufacturing efficiency has grown tremendously in the last 15 years. The long primer bake oven is eliminated and replaced with a compact flash drying step. This is called the Integrated Process because the primer baking step is integrated into the base color plus clear layer process step. These three wet layers are then processed in one baking step as a single multi-layer coating. Removing the primer baking oven saves facility cost, saves energy and reduces carbon dioxide emissions. This new process also eliminates the need for baked primer inspection and sanding.
There is a global mega-trend in automobile painting to utilize this integrated painting process. There are many variations of this new process using solvent-borne coatings and water-borne coatings. The painting footprint and applicators continued to be optimized for higher efficiency.
There is no doubt that Henry Ford would be very happy now, 100 years later, to see how the process time for painting cars is more efficient and is now measured in minutes of process time instead of days! With this comes improved quality, sustainability for environmental targets and best of all a wide portfolio of colors available to the customers!