Damping; Color Dampers; Black Damper; Air Buffering - Brother MFC640CW Service Manual

Damping

Without damping, ink pressure fluctuations directly affect the size of ink-jet head droplets, risking
lower print quality.
The damper structure for black differs from that for the colors (C, M, and Y) because black has
twice nozzles used for each color, meaning higher ink flow rates and bigger pressure fluctuations.

- Color dampers

The three color damper assemblies each have two chambers. The one on the right in the illustration
serves as the damper. The air at the top constitutes a cushion that expands and contracts to absorb
the pressure fluctuations caused by the inertia of the ink in the supply tubes as the head/carriage
unit travels.

- Black damper

The black damper assembly is not partitioned into two chambers. Instead, it has a loose film across
the bottom of its single chamber. This film immediately flexes in and out in response to rises and
falls in pressure, adjusting the chamber volume to counteract pressure fluctuations in the ink supply
tubes.

Air buffering

Liquid ink contains trace amounts of air. These molecules coalesce into air bubbles as the
piezoelectric ceramic actuators vary the pressure on the ink in the ink-jet head channel. (See the
illustration on page 3-13.) Removing as many of these bubbles as possible before the ink reaches
the ink-jet head is essential to maintaining proper print quality. The above illustrations show how
the damper assemblies provide air buffers, the chambers on the left, for consolidating these air
bubbles away from the ink-jet head and vent flow paths for purging them at regular scheduled
intervals.
Color
Black
3-16
Film
This loose film flexes in and out in
response to changes in ink pressure.
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