All printheads include a filter to filter out particles present in the ink or generated upstream of the
filter from reaching the nozzles and causing IQ defects.
In some printers, an additional filter located in the Ink Delivery System is used to capture the particles
before reaches the printhead, increasing the printhead life. Typically, these filters are replaced based
on time or number of liters of ink that has gone through the filter, based on experimental data.
However, depending on the ink type and conditions, the filter may be replaced prematurely when it
has not reached its end of life. In other cases, the filter may be replaced too late, which could end up
in IQ defects or printhead starvation if the flowrate provided to the printhead does not met the
requirement of the print job.
This invention describes a process to trigger the filter replacement based on the ink pressure drop
related to the filter, which is related to the effective area of the filter, thus the clogging of the filter.
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INC, HP, "AUTOMATIC FILTER CLOGGING DETECTION TO TRIGGER MAINTENANCE ROUTINE", Technical Disclosure Commons, (September 17, 2021)