Injet Print head and jets - basic design question

[Bob]

Is there a web page that describes in basic terms how an inkjet head
works ?

Thanks,
Bob

 

[ato_zee]

Is there a web page that describes in basic terms how an inkjet head
works ?

Not as I know of, but it is in the service manuals, the ones with
how to dissassemble and reassemble the printer, with circuit diagrams,
voltages, waveforms and parts list. The action of the head is described
and illustrated.
It's several pages of description, the sequence ends with:-
Appropriate PZT latched by nozzle selector is pushed into the cavity
by applying common voltage from the main board. By this operation,
ink that is stored in the cavity pops out from the nozzles. (Refer to
figure 2.4)
Essentially the PZT (Piezo transducer) expands with the application
of a voltage, acting as a pump. The ink can't go back towards the
cartridge due to flow resistance, so it has to come out through the
nozzle plate. It looks like the channel is folded to increase the reverse
flow resistance and improve pumping efficiency.
If you are thinking of servicing printers you also need the mfrs
service programs that do a lot more than the simple cleaning cycles,
appropriate ribbon cable break outs, and a scope is useful.

 

[Tony]

Not as I know of, but it is in the service manuals, the ones with
how to dissassemble and reassemble the printer, with circuit diagrams,
voltages, waveforms and parts list. The action of the head is described
and illustrated.
It's several pages of description, the sequence ends with:-
Appropriate PZT latched by nozzle selector is pushed into the cavity
by applying common voltage from the main board. By this operation,
ink that is stored in the cavity pops out from the nozzles. (Refer to
figure 2.4)
Essentially the PZT (Piezo transducer) expands with the application
of a voltage, acting as a pump. The ink can't go back towards the
cartridge due to flow resistance, so it has to come out through the
nozzle plate. It looks like the channel is folded to increase the reverse
flow resistance and improve pumping efficiency.
If you are thinking of servicing printers you also need the mfrs
service programs that do a lot more than the simple cleaning cycles,
appropriate ribbon cable break outs, and a scope is useful.

For the sake of completeness.... You are describing the Epson printhead here,
most other manufacturers use thermal technology which works differently.
Tony

 

[drd]

Is there a web page that describes in basic terms how an inkjet head
works ?

yes

http://computer.howstuffworks.com/inkjet-printer3.htm

 

[Gary Tait]

For the sake of completeness.... You are describing the Epson
printhead here, most other manufacturers use thermal technology which
works differently. Tony

Thermal is easy too.The ink sits in a chamber surrounded by a heater. To
shoot a dot, the heater is energised, boils the ink into a bubble, and the
expanding bullbe shoots where it can, out the nozzle, onto the paper.

 

[Bob]

yes

http://computer.howstuffworks.com/inkjet-printer3.htm

Too cool, thanks.

 

[Bob]

Thermal is easy too.The ink sits in a chamber surrounded by a heater. To
shoot a dot, the heater is energised, boils the ink into a bubble, and the
expanding bullbe shoots where it can, out the nozzle, onto the paper.

Thanks to all, the link above is a great reference - complete with
animated illustrations.

Questions:
1. How many jets would a printer like the Epson c86 typically have
per color ?

2. I assume that not all jets fire every time and that the jets that
fire are specific on where the ink needs to be on the paper? That is,
for a specific area of a graphic, the jets that fire are a "random"
pattern based on the distribution of ink needed int the specific
region the head can cover at once?

 

[Arthur Entlich]

Of course, that's just piezo (Epson, etc) head design. Thermal inkjet
printers work quite differently.

Art

 

[Arthur Entlich]

An Epson C86 has 180 black nozzles, 59 each Cyan, Magenta and Yellow.

All this is available in the tech support area of the Epson website BTW.

Each ink nozzle is controlled via electronics and software. There is no
randomness involved, even the "random" looking placement of the dots in
dithering or other distribution on the page is quite specifically
determined through software/firmware.

Art

 

[Bob]

Each ink nozzle is controlled via electronics and software. There is no
randomness involved, even the "random" looking placement of the dots in
dithering or other distribution on the page is quite specifically
determined through software/firmware.

Just to make sure I understand... I was not inferring that the printer
sprayed random patterns... but that the jets used at any particular
time were based on what ink needed to be in what spot on that
particular graphic ? So the head could fire a specific pattern of jets
to spray ink in a variety of spots all at the same time and conserve
head movement?

 

[Gary Tait]

Just to make sure I understand... I was not inferring that the printer
sprayed random patterns... but that the jets used at any particular
time were based on what ink needed to be in what spot on that
particular graphic ? So the head could fire a specific pattern of jets
to spray ink in a variety of spots all at the same time and conserve
head movement?

That is the point essentially. A particular nozzle is fired so it will
put ink where needed, and more nozzles rill require less head passes.

I my Canon Pixma ip5000 has 320 nozzles for pigment black, 256 each per
photo ink (CMYK), plus 256 each for a micro nozzle (CM), making a total
of 1856 nozzles.

 

[Arthur Entlich]

The printer driver determines how the nozzles will express the ink
image. Most printers overprint the same area several times, although
they do so by filling in the spaces. This is in part how they produce
the resolution they do. So, a printer may print 8 lines of information
one dot thick, with one dot space between each line. Then the printer
moves the paper 1/216th of an inch or whatever, and the print fills in
the missing dots. By doing it in this manner they can up the resolution
further, since multiple swipes of the head allow for reduced wet ink (it
has time to dry between swipes) and less actual required density per swipe.

Art