HP Designjet H45000 HP Designjet H35000 and H45000 Printer Series - Headstrike - Page 4

Late Jets, Intermittent Jets

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Intermittent Jets These jets may pass an AutoJet or AutoSet calibration, but when printing begins they drop out. The jets have some small solid particle lodged within the jetting nozzle or orifice. As the particle moves around, it can alternately allow the jet to fire or it can block the jet completely. Printing a Manual Jet Mapping page immediately after canceling a print job will often reveal the intermittent jet as missing or as producing a wavy line in the Manual Jet Mapping pattern, as shown below at jets 62 and 77. Jets showing this phenomenon are usually unrecoverable. Because AutoJet may continue to find them as usable, the best option is to use Manual Jet Mapping to identify them as "Hard" jet outs, so that AutoJet will not no longer attempt to evaluate them and mark them as good. Once manually mapped out as "hard", the jets will remain on the bad jet list until such time that an operator deliberately clears the Hard Jet-Out list. "Late" Jets These jets appear to fire late (or early, depending on the direction of the carriage). Headstrikes or other damage, such as improper cleaning of the printhead, have created small scratches on the orifice plate around the jets. Small amounts of ink accumulate within the scratches (held in place by surface tension) and create a film of ink that must be penetrated by new ink droplets when the jet fires. The required effort to penetrate through this film is enough to delay the drop, creating the characteristic parabola shape in one area of the Prime Bars pattern for that head. 4

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Jets showing this phenomenon are usually unrecoverable. Because AutoJet may continue to
fi
nd them as usable, the
best option is to use Manual Jet Mapping to identify them as “Hard” jet outs, so that AutoJet will not no longer attempt
to evaluate them and mark them as good. Once manually mapped out as “hard”, the jets will remain on the bad jet
list until such time that an operator deliberately clears the Hard Jet-Out list.
“Late” Jets
These jets appear to
fi
re late (or early, depending on the direction of the carriage). Headstrikes or other damage, such
as improper cleaning of the printhead, have created small scratches on the ori
fi
ce plate around the jets. Small amounts
of ink accumulate within the scratches (held in place by surface tension) and create a
fi
lm of ink that must be penetrated
by new ink droplets when the jet
fi
res. The required effort to penetrate through this
fi
lm is enough to delay the drop,
creating the characteristic parabola shape in one area of the Prime Bars pattern for that head.
Intermittent Jets
These jets may pass an AutoJet or AutoSet calibration, but when printing begins they drop out. The jets have some
small solid particle lodged within the jetting nozzle or ori
fi
ce. As the particle moves around, it can alternately allow the
jet to
fi
re or it can block the jet completely. Printing a Manual Jet Mapping page immediately after canceling a print
job will often reveal the intermittent jet as missing or as producing a wavy line in the Manual Jet Mapping pattern, as
shown below at jets 62 and 77.
4