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Abstract

We provide a method of printing using a multi-nozzle ink jet print head having a pressure modulator for causing streams of ink emitted from the nozzles to be broken up into individual droplets. The nozzles are divided into a plurality of groups of nozzles, and groups of charge electrodes correspond, each group of charge electrodes having a respective charge controller. In the method a modulation waveform is generated to operate the pressure modulator to cause droplets to be generated in each stream. Independently for each group of charge electrodes, the respective charge controller is operated to supply a charge signal waveform to each charge electrode in turn, the phase of the charge signal waveform relative to the modulation waveform is adjusted between 0 and 360 degrees in a number of steps, and the optimum phase relationship to achieve proper charging for each droplet stream is determined in turn. Thereafter the phase of the charge signal waveform relative to the modulation waveform is adjusted to achieve charging of droplets in all the streams in the group simultaneously.

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First Claim