Patent ID: 6464322
Filing Date: 2002-10-15
Classification: B41J

Abstract:
Process for compensation of mechanical defects in an ink jet printer by adjusting the arrival position on a substrate (27) of electrically charged ink droplets in an adjustable manner using charge electrodes (20), the droplets originating from a print head (25) and the trajectories of the droplets being modifiable by deviation electrodes (23, 24) between N positions, between a first position X1 and a last position XN and with Nâˆ’2 intermediate positions, the N positions defining a frame in the form of a straight line segment approximately parallel to an X direction of the substrate (27), the process being characterized in that the following parameters are servocontrolled at all times during operation of the printer:an ink viscosity value that remains within a predetermined tolerance as a function of its temperature, by adding solvent or ink with a higher concentration of coloring agents, a jet velocity by acting on the ink supply pressure, a distance at which the jet is broken into droplets by acting on an adjustable parameter to maintain a predetermined breaking distance, a phase difference between instants at which electrical droplet charge pulses are applied and instants at which droplet formation pulses are applied by action on a timer circuit, and in that the following steps take place during a phase prior to the print phases: a) a pattern is printed, b) the said printed pattern is compared with a reference pattern to deduce an algebraic difference &Dgr;Xi between a real observed position and a corresponding nominal position, for the said print head and for an integer number a of positions, where a is greater than or equal to 2 and less than or equal to N, for each of the chosen a positions, where i varies from 1 to a, c) a static translation error &thgr; is determined as being the difference between the center of gravity of the a actual observed positions and the center of gravity of the corresponding a nominal positions, d) for each of the a observed droplet positions, a position error &dgr;1 is observed between the real position of each droplet corrected by the translation error and the nominal position of each droplet, e) the value &thgr; of the static translation error and the values &dgr;1 of the droplet position errors from their initial nominal positions, are memorized, then, in each phase in which a pattern is printed defined by a set D of numeric data, a correction value to a nominal voltage is determined for each droplet to give a corrected value to be applied to the electrodes, this calculation taking account of the memorized values of static translation and position errors, the data extracted from the set D of numeric data defining the pattern to be printed, and row j, where j is between 1 and N, of the nominal target print position.