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Question What is the Purpose of Dampers in a Print Head Carriage?

Discussion in 'General Chit-Chat' started by David40, May 9, 2020.

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  1. David40

    David40 Member

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    It's just a basic question about what they are supposed to do. I am curious to know the function or purpose for the dampers that sit above the print head, and why they would need to be changed a regular intervals? They look like little tanks with baffles and don't appear to have any moving parts so how can they wear out and need replacement?
    Someone please enlighten me.
    Thanks
     
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  2. signage

    signage Major Contributor

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    Dampers are use as a reservoir for ink colors to the channels of the head. They hold ink colors and allow for any air bubbles to be removed before the ink goes into the head, they also have micron filters in them.
     
  3. David40

    David40 Member

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    Filters right at the head sounds like a good idea. Sort of like a fuel filter for a vehicle. I read somewhere that they recommend replacing the dampers after a certain period of time, but wouldn't it make more sense to base the maintenance on usage rather than time? There is going to be a big difference between someone that is using up cartridges of ink every week compared to someone that needs to replace ink cartridges every six months. Is that reasonable?
     
  4. Notarealsignguy

    Notarealsignguy Very Active Member

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    Its not really a filter, its more of a strainer to catch a random chunk of dried ink. A year is fine because you really shouldnt be plugging these up at all, if you are then you have another issue happening upstream. I bet most people don’t replace them until some issue shows up. Were 3 years on ours. Very few change car fuel filters either.
     
  5. netsol

    netsol Very Active Member

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    over the years i have serviced many types of printing equipment, for many industries.
    to me in simplest terms, the dampers allow that manufacturer to "cheat" and move 6 colors of ink with 1pump (8 colors with 3 pumps, you get the idea). the damper is a flexible container that gives the ink somewhere to go since the pumps are almost positive displacement type. (first thing you learn in physics is youncan't compress a liquid) we pump more yellow than we need to replace (from the previous pass) & the damper puffs up like a pufferfish.
    then the ink goes back to the cartridge, as pressure equalizes

    it always seemed funny to me, that they eliminated a couple pumps on a printer that cost close to twice the price of the compact car my tech ws driving when he went to fix the printer
     
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  6. David40

    David40 Member

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    Interesting, so they actually do have a moving part of sorts if there is some kind of a diaphragm that is expanding and contracting. I suppose if that diaphragm fails you could have a real mess on your hands.
     
  7. MikePro

    MikePro Major Contributor

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    love netsol's explanation. huge +1.

    I only changed the dampers when I needed to replace printheads....so maybe each damper saw 1-2 replacements in 10years.
    I feel like I never NEEDED to change the dampers, but figured while I was replacing a $500+ printhead that I would replace the $10 damper while I was at it....especially since when you remove/reinstall, you slightly weaken the seal between the damper/oring/printheadmanifold, and a proper seal makes the system work as it was designed.
     
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  8. Jim Hancock

    Jim Hancock Active Member

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    Dampers perform 4 functions.
    1. Ink supply reservoir for the print head.
    2. The screen helps filter out any junk in the ink.
    3. They act as a "pump". There is spring plate behind the clear film diaphragm in some dampers or the round button on others which has a spring behind it. As the print head uses ink and the damper empties, the diaphragm gets pulled inward and starts compressing the spring mechanism. At some point, the spring mechanism is pulled inward to the point that it pushes back out, pulling ink in from the ink line and cartridges.
    4. The term "damper" comes from the other primary action it performs, which is to dampen and regulate pressure changes in the ink line at the print head as it rapidly stops and reverses direction. As it stops, the pressure momentarily increases and when it starts back in the other direction, it momentarily decreases, due to inertia. These pressure variations are not good for the delicate internal crystal structure of the print head, so some sort of control is needed. This is why the ink lines are not hooked directly to the print heads. The dampers absorb these minor pressure deviations.
    Damper failures can be caused by a number of things. The spring can start getting weak, so it doesn't "pump" correctly. The "O" ring that seals the connection to the manifold can start leaking air, resulting in dropout banding or ink dripping from the bottom of the head. One of the clues you have a damper is failing is when the missing nozzles on your nozzle test keep moving around between cleanings.

    Hope this info helps...
     
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  9. netsol

    netsol Very Active Member

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    absolutely right jim

    i was making a point about one of those functions
     
  10. netsol

    netsol Very Active Member

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    absolutely right jim

    i was making a point about one of those functions
     
  11. Jim Hancock

    Jim Hancock Active Member

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    Agree with everything you said! For being such a simple looking little part, it is actually somewhat complex.
     
  12. Texas_Signmaker

    Texas_Signmaker Very Active Signmaker

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    Good information. Had no idea those cheap plastic things served such function.

    My chevy doesn't have a serviceable fuel filter.. they must be phasing those things out.
     
  13. player

    player Major Contributor

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    They aren't really so cheap. My VP uses 8 of them. They are about $35USD each, so almost $300 to change them out. Plus the cost of the little rubber o-ring.

    Something someone told me recently is if you change the black head and damper be sure to clean the black line. It gets all clogged up with carbon and will reduce the life of the new head.
     
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  14. The Big Squeegee

    The Big Squeegee Major Contributor

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    Great information! Here I thought the function of the dampers was to keep the ink from flowing back to the carts while holding enough ink to keep the heads supplied.
     
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