Patent ID: 6325494
Filing Date: 2001-12-04
Classification: B41J

Abstract:
A method for adjusting a modulation waveform amplitude in a multi-nozzle continuous ink jet printhead having a piezoelectric oscillator for causing streams of ink emitted from the nozzles to be broken up into individual droplets, the nozzles being divided into a plurality of groups of nozzles, and corresponding groups of charge electrodes, each group of charge electrodes having a respective charge controller, the method comprising,generating a modulation waveform to operate the piezoelectric oscillator to cause droplets to be generated in each stream;generating in said charge controllers, charge signal waveforms to apply charging voltages to the charge electrodes; andadjusting the modulation waveform amplitude in increments and at each of the said increments:determining a phase relationship between the charge signal waveforms applied by the charge controllers and the modulation waveform to achieve satisfactory charging of the droplets;determining a determined spread of the phase relationships across all the streams to achieve satisfactory charging of the droplets from each nozzle; comparing the determined spread of the phase relationships with a previous narrowest spread determined in a previous increment to be the narrowest and, if the determined spread is narrower than the previous narrowest spread, recording the determined spread as a narrowest spread;and, thereafter setting the modulation waveform amplitude to the modulation waveform amplitude to an increment having a narrowest spread of phase relationships.