Printing Process; Printing Methods - Epson Stylus Color 1520 Service Manual

2.2.2.2 Printing Process

The stages below describe how with the on-demand ink jet system ejects ink from each nozzle.
Step 1 Normal state
When no print signal is output, the PZT does not move and the pressure in the cavity is kept at a constant
level.
Step 2 Ejecting state
A print signal is output by the head driver board to a specific nozzle to drive the PZT. The voltage is
produced in the common driver circuit board on the control board. When voltage is applied to the PZT, the
PZT moves and the pressure in the cavity changes. This operation causes the ink in the cavity to spurt out
from the nozzle.
Normal State
Cavity
Nozzle
During ink charging or cleaning, negative pressure in the cavity absorbs the ink from the cartridge to refill the
cavity. The unused ink adheres to the nozzle surface and increases viscosity in the nozzles, causing low
printing quality. To prevent this problem, the ink is periodically absorbed and sent into the waste ink drain
pads by the pump mechanism. Ink viscosity tends to change with the temperature around the printhead. To
prevent this, a thermistor is attached to the driver circuit board. This is used to determine the proper drive
pulse automatically based on the detected temperature.

2.2.2.3 Printing Methods

This printer has special printing modes for various types of graphic images.
Y
Double-Firing Normal Dot / One Dot Print Modes
In ANK or bitmap image mode the printer forms 1 dot with double ink ejections. In raster graphics mode,
which requires high-resolution, it forms 1 dot with a single ink ejection.
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EPSON Micro Dot Printing
Both black and color printouts can be made in normal dot print mode and EPSON micro dot print mode.
In the normal dot print mode, the printer uses less ink to create sharper dots. This expands the gradation
range for a more delicate tone. This mode is available when 1440 × 720-dpi-paper or glossy film is
selected.
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Microweave Printing
In this mode, nozzles to be activated are divided and only specific nozzles are used for each pass. The
paper is fed in smaller increments for this operation. This mode eliminates white banding that can occur
between lines, resulting in improved graphic images. This mode does have a decreased feed speed.
Microweave printing can be selected through the printer driver.
Piezo
Figure 2-3. Printing Operation States
Ejecting State
Ejected Ink
Operating Principles
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