Brother GTX-4 Service Manual page 40

<TIPS: Development of air bubbles>
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Minor quantities of air are dissolved in the fluid ink. The quantity of the dissolved air changes depending on the pressure applied.
Under high pressure conditions, the quantity of saturated air content increases, causing more air to dissolve into the ink. When
the pressure decreases, the quantity of saturated air content is reduced to cause the air to escape from within the fluid.
Once an air bubble is created, the pressure variation from the piezoelectric actuator causes it to expand and contract accordingly.
The bubble contracts when the pressure within the tubings increase, forcing air within the bubble to dissolve into the surrounding
fluid. Although the quantity of air per unit area passing through boundary between the ink and bubble is constant, the surface
area of the air-ink boundary decreases, causing the air passing through into the ink to decrease in proportion to the reduction of
the surface area.
When the pressure within the tubings are reduced, the air dissolved in the fluid attempts to escape and pass through into the air
bubble. As a result, the air bubble expands and increases the surface area of the air-ink boundary, causing the quantity of air
passing through from within the fluid to increase in proportion.
The air bubble within the ink gradually develops in size with the repeated contraction / expansion of the air bubble under the
variation of the pressure applied to the ink.
In order to prevent such occurrences, air is adequately purged and flushed during the printing process to constantly supply fresh
ink free of air bubbles and dissolved air to the front-end.
Pressure within the ink tubings
High
Bubble
Ink
: Pressure
: Air flow
Before Using Your Printer for the First Time
Low
1-26
Bubble
Ink