Epson Stylus Photo785EPX, Service Manual

Page: 33 / 192

EPSON Stylus PHOTO 895/785EPX/915/825 Revision B
Operating Principles Overview 33
2.1.2 Printhead
The printhead uses a new developed U-CHIPS head and Stylus PHOTO 895/785EXP/
915/825 can perform multiple shot printing and variable printing.
The CSIC 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.
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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.
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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.
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Nozzle Plate
The board with nozzle holes on the printhead surface is called Nozzle Plate.
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CSIC Connection Circuit
This circuit connects the CSIC mounted on the ink cartridge and the main board.
One end of the wire harness connects with the print head cable to the main board.
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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.
Figure 2-2. Printhead Sectional Drawing
Nozzle Selector Board
Needle
Ink Cartridge
Filter
Cavity
PZT
Nozzle Plate
CSIC
CSIC Connection Circuit