Printhead; Printing Process - Epson Stylus Color C70 Service Manual

EPSON Stylus COLOR C70/C80

2.1.2 Printhead

The printhead uses a new developed P-MACH head and Stylus COLOR C70/C80 can
perform variable dot printing.
The CSIC-chip is mounted on the ink cartridge. By storing ink life data, this IC makes
it possible to control the ink in ink cartridge unit.
The basic operating principles of the printhead, which plays a major role in printing,
are the same as previous models; on-demand method which uses PZT (Piezo Electric
Element). In order to uniform the amount of ejecting ink, the printhead has its own
head ID (13 digits for this printhead) which adjust PZT voltage drive features.
The printhead stores the head ID to EEPROM and generates appropriate PZT drive
voltage to prevent amount of ink from varying by printheads.
Following explains printhead basic components.
PZT
PZT is an abbreviation of Piezo Electric Element. Certain amount of voltage
expands and contracts PTZ. The drive wave generated on MAIN board drives PZT
and PZT pushes the top cavity which has ink stored to discharge the ink from each
nozzle on the nozzle plate.
Ink Cavity
The ink absorbed from the ink cartridge goes through the filter and then is stored
temporarily in this tank called "cavity" until PZT is driven.
Nozzle Plate
The board with nozzle holes on the printhead surface is called Nozzle Plate.
Electrodes for CSIC-chip
The communication between CSIC-chip and main unit is performing via the
electrodes on the carriage.
Filter
When the ink cartridge is installed, if any dirt or dust around the cartridge needle is
absorbed into the head, there is a great possibility of causing nozzle clog and
disturbance of ink flow, and finally causing alignment failure and dot missing. To
prevent this problem, a filter is set below the cartridge needle, where ink is filtered.
Operating Principles
Nozzle Plate
Figure 2-2. Printhead Sectional Drawing (Image)

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 C424 MAIN-B board, IC (Nozzle
Selector) located on the printhead unit latches data once by 1-byte unit.
Overview
CSIC-chip
Nozzle Selector Board
Ink Cartridge
Needle
Electrodes for CSIC-chip
Filter
Cavity
PZT
Revision A
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