Drop sensing and recovery system for an ink jet printer

A method of maintenance of a full width array printhead in an ink jet printer, the printhead having a linear array of nozzles in a nozzle face of the printhead, the maintenance method comprising the steps of:

• translating a translatable carriage parallel to the array of nozzles in the printhead, the carriage having mounted thereon a droplet sensor and a recovery device;
• monitoring the location of the droplet sensor and recovery device relative to the nozzles as the carriage is being translated;
• selectively ejecting a droplet from each nozzle when the droplet sensor reaches a predetermined position in alignment with the nozzle from which a droplet is to be ejected;
• sensing a droplet ejected from each nozzle in the array of nozzles one nozzle at a time by the droplet sensor mounted on said translatable carriage;
• determining whether a droplet was ejected by the droplet sensor and, if a droplet was ejected, determining whether the trajectory is within the limits of a predetermined directionality of trajectory followed by the elected droplet;
• identifying a problem nozzle in the nozzle array by detecting either the absence of an ejected droplet or a deviation of the droplet trajectory outside the limits of a predetermined directionality;
• on a subsequent translation of the carriage, performing a predetermined recovery operation on each identified problem nozzle, and
• sensing a droplet ejected from each problem nozzle for which a recovery operation was performed to confirm full recovery and re-performing a predetermined recovery operation not fully recovered.