The print head unit 1, wherein the parallelism adjusting means comprises at least one piezoelectric motor and at least one capacitive sensor, and the at least one piezoelectric motor is configured for actuating the first print head and the second print head by closing {HEAD ~ a loop} with {TAIL ~ the at least one capacitive sensor} 
The print head unit 1 , wherein the parallelism adjusting means comprises at least one piezoelectric motor and at least one capacitive sensor , and the at least one piezoelectric motor is configured for actuating the first print head and the second print head by closing { HEAD ~ a loop } with { TAIL ~ the at least one capacitive sensor }
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