Method of measuring a wetting property of a nozzle plate

1. A method of measuring a wetting property of a nozzle plate in a droplet expelling device having a number of nozzles formed in the nozzle plate, each one of the nozzles being in fluid communication with a pressure chamber, and an actuator system for expelling a droplet of a liquid from each of the nozzles, the method comprising the steps of:

applying an amount of liquid onto a surface of the nozzle plate;

observing the nozzle plate with the liquid applied thereon; and

determining the wetting property from a distribution of the liquid on the nozzle plate,

wherein the amount of liquid is applied onto the nozzle plate by expelling liquid through the nozzle, and

wherein the liquid is expelled by energizing the actuator system with an energy that is insufficient for expelling a droplet.

2. The method according to claim 1 , wherein each one of the number of pressure chambers is in communication with an ink reservoir, the ink reservoir being provided with pressurizing means for providing a pressure pulse to said ink reservoir, wherein the liquid is expelled by providing a pressure pulse to the ink reservoir.

3. The method according to claim 1 , wherein the droplet expelling device is an ink jet print head.

4. The method according to claim 1 , wherein the liquid that is applied to the surface of the nozzle plate is ink.

5. The method according to claim 1 , wherein the print head is moved from an operating position, where it is used for printing an image, to a cleaning station, and the amount of liquid is applied onto the surface of the nozzle plate while the print head is in the cleaning station.

6. A method of measuring a wetting property of a nozzle plate in a droplet expelling device having a number of nozzles formed in the nozzle plate, each one of the nozzles being in fluid communication with a pressure chamber, and an actuator system for expelling a droplet of a liquid from each of the nozzles, the method comprising the steps of:

applying an amount of liquid onto a surface of the nozzle plate;

observing the nozzle plate with the liquid applied thereon; and

determining the wetting property from a distribution of the liquid on the nozzle plate,

wherein the amount of liquid is applied onto the nozzle plate by expelling liquid through the nozzle,

wherein the nozzle plate is observed by capturing a digital image of the nozzle plate with the liquid applied thereon, and

wherein the wetting property is determined by analyzing the digital image.

7. The method according to claim 6 , wherein the print head is moved from the cleaning station to a position of a camera for capturing the digital image after the liquid has been applied.

8. An ink jet printer having a print head with a nozzle plate and a number of nozzles formed therein, each one of the nozzles being in fluid communication with a pressure chamber and an actuator system for expelling droplets of ink from each of the nozzles, the printer further having a control system and a camera arranged to capture an image of the nozzle plate, wherein the control system is configured to perform the method according to claim 4 .

9. The printer according to claim 8 , wherein each one of the number of pressure chambers is in communication with an ink reservoir, the ink reservoir being provided with pressurizing means for providing a pressure pulse to said ink reservoir.

10. The printer according to claim 8 , wherein a cleaning station for cleaning the nozzle plate is disposed between the camera and a media transport system.