Epson 680Pro - LQ B/W Dot-matrix Printer Service Manual page 32

EPSON Stylus COLOR 680/777/77i
2.1.2.1 Printing Process
This section explains the process in which the printheads of On-Demand inkjet printers
eject ink from each nozzle.
1. Normal State:
When no printing signal is sent from PC, or no PZT drive voltage is applied, PZT
does not change shape, therefore PZT does not squeeze the cavity. Ink pressure
inside the cavity is kept normal. (Refer to Figure 2-3.)
2) Ejecting State:
When the print signal is output from the C383 MAIN board, IC (Nozzle Selector)
located on the printhead unit latches data once by 1-byte unit. An appropriate PZT
latched by the nozzle selector is pushed into the cavity by the common voltage
applied from the main board. By this operation, ink stored in the cavity spurts out
from nozzles.(Refer to Figure 2.1.2.2.)
Ink Path
Nozzle
PZT drive voltage
Figure 2-3. Printhead printing process
Operating Principles
PZT
Ink Cavity
Nozzle plate
2.1.2.2 Printing Method
For print dot system, Stylus COLOR 680/777/777i has the following two kinds of
printing modes.
n Multiple shot printing
n Variable dot printing
The above two printing modes are automatically selected depending on the media and
the resolution setting of the printer driver. The following explains each printing mode.
o
Multiple shot printing
This printing mode is developed to improve the print quality on plain paper or
transparencies in low resolution. The multiple shot printing mode uses normal dot
and the number of dot shots varies from 1 shot to maximum 4 shots depending on
the print data to enable sharp image output even in a low resolution.
o Variable dot printing
This printing mode is developed to improve the print quality on exclusive paper.
This mode is basically the same as variable dot printing mode used on other
products /; micro dot, middle dot, and large dot compose this mode. Print dot size
varies according to print data and this mode enables even sharper image output on
exclusive paper.
Overview
Revision B
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