A solution for different colours and recipes
Artic, a Romanian company producing freezers, was looking for an automatic solution to paint over 27 types of parts with 2 different colours and recipes. The Akzo Nobel paint used, is a 2 component finishing paint, but has to be thinned to be applied correctly on a plastic surface with a 25µm film.
The ratio recommended by the producer was 7:1 for paint with hardener, and 2:1 if you take (A+B):C, volume C being larger than B. Artic used to apply this with a low exit 100 cc/min gun and when thinner was applied, they used a 2KS station and mixed A+C with 10:1 ratio. However, in this case, it was hard to measure component B.
One recipe for (A+B):C
To avoid human error in the mixing process and to avoid mixing component A with C (thinner) and after that mixing with component B, the local distributor, SC Romcrete Echipamente SRL, suggested a 3 component automated installation. The implemented solution has a self-learning robot fed by a 3 component paint line and works with conveyer and cure oven. The 3KS station works in low pressure with Graco Triton pumps for all components, even for the cleaning solvent.
For a low volume of component B, a Corriolis 1/8 high resolution flow meter was used. The result was one recipe for colour A:B at a ratio of 7:1 and one for (A+B):C at a ratio of 2:1. Using a conventional paint spray gun for high production and good atomization, flow increased to 150cc/min for the robot’s full speed. To avoid pulsation at the gun during pump change-over to component C, a fluid regulator of the mixed product is placed on the robot arms near the gun with a 5 m hose.
Mixed component viscosity was tested and the results were as expected: no errors in the mixing process and the ratio had a tolerance lower than 5%.