Front End Components And Their Main Roles; Nozzle Array (Head Bottom Plate); Ink Spray Function; Piezoelectric Plate - Brother MFC640CW Service Manual

Front end components and their main roles

- Piezoelectric plate

Applying a voltage stretches the plate, serving as the actuator for spraying ink. Consisting of thin
piezoelectric plates laminated together, this plate can be driven even by a low voltage.
- Filter
This removes foreign matter from the ink.
- Metal plates
These form the print nozzle pressure chambers, ink flow paths, and manifolds.
- Nozzle plate
This plate has 370 nozzles in five staggered lines with 74 nozzles each: two (148 nozzles) for
black and one each for the three color inks.
- COF
This flexible circuit board holds the piezoelectric driver chip.

Nozzle array (head bottom plate)

Print head travel direction
0.1693 (1/150")
74
73
72
71
5
4
3
2
1
Black odd
Black even
Ink-jet unit

Ink spray function

The head employs drop-on-demand ink-jet printing.
Print commands to the drive circuit apply a bias voltage to the layer electrodes on the piezoelectric
ceramic surface stretching the elements perpendicular to that surface. Drive signals removing this
voltage for specific channel electrodes allow the piezoelectric elements to return to their original
shape, sucking ink into the corresponding channels*. Reapplying the bias voltage stretches the
elements once again, applying pressure to the ink, spraying it from the print nozzle. The ink drop
hits the paper on the platen, forming a dot.
*Pressure chambers for individual nozzles
7.4507 (44/150")
7.2813 (43/150")
4.9107 (29/150")
Magenta
Cyan
Yellow
3-13
Channels
Nozzles
Confidential