4 ] Ink Cartridges - Brother MFC620CN Service Manual

[ 4 ] Ink cartridges
Ink cartridge features
This machine uses four ink cartridges: a black one and three color ones with a slightly lower
capacity.
Previous versions featured horizontal insertion over metal needles fixed to the chassis. This one
features vertical mounting in the ink refill base over plastic needles.
This vertical arrangement requires two ports in the bottom of the cartridge: one supplying the ink
for printing and another supplying air to replace that ink. Both ports have disc valves preventing
ink leakage. Mounting a cartridge over the plastic needles in the ink refill base forces these valves
open to secure flow paths for both the ink and the air.
Inks
"Removing air"
An earlier page explained how too much air in the ink risks air bubbles degrading ink-jet
performance. The manufacturing process prevents such air bubbles with a step, deaeration, that
removes air from the ink before injection into the cartridge. Vacuum packaging then prevents air
contamination during shipping and storage.
"Pigment-based ink"
Previous Brother machines used only dye-based inks. This one switches to a pigment-based ink for
black only, reducing fuzziness from print character outlines, boosting resolution for black dots, and
producing clearer images on plain paper.
This machine provides separate head caps and individual vent unit drive mechanisms for this black
pigment-based ink and its dye-based color counterparts. Such special design measures are
necessary because any mixing of the two types triggers a chemical reaction producing residue
clogging head nozzles, filters, maintenance unit piping, and other components, degrading print
performance.
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