Patent ID: 7467840

Claim:
A method for controlling volume of droplets of printing fluid ( 18 ) emitted from a print head ( 1 , 2 ) during a printing process; said print head ( 1 , 2 ) having: at least one pump ( 10 , 20 ) having an inlet for taking in the printing fluid ( 18 ), a pump chamber ( 11 ) for containing the printing fluid ( 18 ) and an outlet for letting out printing fluid ( 18 ); and an actuator ( 16 ) for generating actuation pulses acting on the printing fluid ( 18 ) in the pump ( 10 , 20 ); said method comprising the following steps: determining a first characteristic frequency of the pump ( 10 , 20 ) during a first measurement; actuating the actuator ( 16 ) at least one time in order to generate an actuation pulse which causes at least one droplet of printing fluid ( 18 ) to be emitted from the pump ( 10 , 20 ) during a first printing action; determining a second characteristic frequency of the pump ( 10 , 20 ) during a second measurement; comparing the second characteristic frequency to the first characteristic frequency; and determining the value of the actuation pulse which needs to be generated by the actuator ( 16 ) for the purpose of causing at least one droplet of printing fluid ( 18 ) to be emitted from the pump ( 10 , 20 ) during a second printing action on the basis of a difference found between the first characteristic frequency and the second characteristic frequency, and on the basis of requirements regarding the volume of droplets of printing fluid ( 18 ) to be emitted during the second printing action.