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 user 2009-12-01 at 11:53:56 am Views: 39
  • #23031

    How an inkjet nozzle fires 36,000 times a

    The precision needed for an inkjet nozzle to work is
    like dropping a grape from a 30-storey building and hitting a bucket on
    the pavement below. Now that’s accurate. But in the case of an inkjet
    nozzle it’s also doing it 36,000 times a second, not bad for something
    which is the third of a width of a human hair.The drops fall at a speed
    of 50kmph – 35 million of them for every 6 x 4 photo you print.We took
    the short hop over to Dublin, Ireland to check out HP’s DIMO (Dublin
    Inkjet Manufacturing Operation) facility where it develops and
    manufactures ink cartridges.

    Each new ink takes three to five
    years to develop and goes through thousands of different formulas.”Ink
    is the hardest working part [of inkjet printing],” explains HP’s Thom
    Brown. “One change or minor alteration could make a huge impact. It’s
    wet but when you want it to be on the paper you want it to be dry,” he

    HP came to Dublin in 1995, helped by IDA grants and has
    established a massive, 200-acre site. Intel’s operation had already
    been in the area for a few years. The site is a mix of R&D and some
    low-level manufacturing.

    How cartridges are made
    At the
    facility we saw tri-chamber cartridges being made with integrated print
    heads. The early part of the manufacturing process involves putting a
    filter then sponge into the cartridge. It’s essential that the right
    material is used to deliver the correct amount of ink to the nozzles –
    too much or not enough ink can result in the nozzles being starved or

    HP dimo
    Everything about the process is designed so
    no contaminants can get into the cartridge or that the different
    chambers inside the cartridge can’t contaminate one another. The
    cartridges itself flies around the facility on small conveyors.According
    to our guide, they can always track back if something has gone awry in
    the process – the cartridges all have an individual 16-digit ID laser
    etched on them along with a date. The lid is placed on and sealed before
    the cartridges are filled and everything is tested to stop
    leakage.Attaching the print head is also a delicate process. Adhesive is
    applied on the area where the head will go, while the Tab Head Assembly
    (the flexible print head) is attached precisely. Any problem here and
    the head won’t line up inside the printer. The THA is made with
    specifications at single-digit micron levels using a microscopic welding

    HP dimo
    The chip wafers are manufactured elsewhere.
    The so-called banner material is drilled using sand or laser in a
    process that creates the minute channels for ink to flow through. The
    material is laid across the wafer, but as it is UV curable, it needs to
    be kept away from UV, hence the lab we saw was bathed in yellow light.
    Another layer, the plating, has the holes through which the ink is
    actually forced and the different layers are then bonded and connected
    to each other.

    Filling and testing
    Then we move on to the
    filling process. This is the “Wet Loop.” What about the toxicity of
    inks, we ask – is it possible to have non-toxic inks? “We use the lowest
    amount of toxicity versus effectiveness” says our guide.Four cartridges
    are filled at any one time, taking four to five seconds to fill each of
    them in a vacuum.A high pressure is used to fill the cartridges from
    1,000 litre tanks which are rolled around the facility. A huge ink
    splodge on the ceiling is the result of a time when the pressure got a
    little too much.After the cartridges are filled, the nozzles are fired
    to test them. A vent in the top of the cartridge enables air to replace
    the ink as it’s used, though access is via a labyrinth channel to
    prevent ink evaporation.After a test print, the nozzles are sealed by
    the tape that you remove when you install them in your printer.Finally,
    the cartridges are sealed and loaded into boxes and sent elsewhere to be
    placed in their sale packaging.

    HP dimo
    The electrical
    process is tested out at several stages throughout the process and
    techniques such as X-rays are used to see inside the cartridge as it
    prints in a special test area filled with tens of printers and old
    machines. An autopsy area seeks out the causes of problem cartridges.
    Long-life testing also takes place here.

    HP dimo
    “The physics
    of what happens inside a printer is quite extraordinary,” says HP’s Pat
    Harnett. “There’s mathematics, temperature, process and fluid dynamics.
    It takes a lot of tuning to get it right on different papers.”"It’s not
    as simple as millilitres of ink – there’s a lot more behind that in
    terms of the nozzle balance. And it’s not just about millilitres, it’s
    about pages.”

    HP dimo
    But how much of the cartridge uses
    recycled material? According to Harnett, it was 70 per cent in 2008.
    “You want an HP cartridge that’s made of a recycled material but with
    all the benefit of buying an original HP cartridge. There’s a mixture of
    both using content and complete recycling,” he explains.”Virgin
    material is much easier from a technologist’s point a view. In recycled
    content there’s the possibility of interaction with the ink. We need to
    get the wall thicknesses correct for example. A lot of research has to
    go into it. The difference between 70 per cent and 80 per cent [is] a
    lot of effort.”