The rotary cup front valve set selection cannot only compare the "valve switching time" or the "fastest color change seconds" in the advertisement. What really determines the color change rate and residual level is the total wet end volume, dead angle, valve seat structure, pipe length, return path, cleaning medium, air pulse, control timing and first piece judgment criteria from the color valve outlet to the cup head. For multi-color, high-frequency color-changing automotive parts lines, the wet end volume should be small, the valve part is close to the rotating cup, there is no obvious blind cavity, the color/cleaning/air/return path is independent, maintainable and verifiable, and the color-changing time, string color, detergent residue, scrap lacquer and the qualified rate of the first part should be confirmed by the actual coating, the most unfavorable color combination and the continuous color-changing fat/sat.
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