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Thread: Bubble in laser tube

  1. #1
    Join Date
    Aug 2018
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    UK
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    Bubble in laser tube

    I've just filled the laser tube for the first time in my DIY laser. It's an EFR F2 80W. It says the flow rate can be as low as 2 litres a minute and I just measured mine at 2.6l/min so I assume ok. However, there is a bubble in the glass tube and it's not moving. There are loads of really tiny ones too but I'm guessing they will dissapate in time. The laser tube is level as directed by the EFR installation details. I could probably adjust to give it a very slight uphill in necessary. The thing is though, do I need worry about the bubble? I have attached a photo.
    Attached Images Attached Images

  2. #2
    Join Date
    Mar 2011
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    I don't know for sure that a bubble there would cause a real problem - the hot side of the tube is still in contact with water, however I would not be comfortable with it.

    The laser tube does not need to be perfectly level. In fact the tube could be at nearly any angle and still work just fine as long as the first mirror can steer the beam towards the second mirror. I adjust my tubes so that the output end is about 1/2" higher.

    Another thing you can do is just let the water run for a long time. Eventually the bubble should disappear.
    Shenhui 1440x850, 130 Watt Reci Z6

  3. #3
    Join Date
    May 2015
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    FL
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    Very simple solution.
    Add about 2-3 drops of dawn dish soap to the water and wait about 24 hours. It helps break the surface tension and gets the bubbles moving.
    Works every time.
    Jeff Body
    Go-C Graphics

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  4. #4
    Join Date
    Aug 2018
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    UK
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    Thanks Rich, Jeff. I've raised the front of the tube as far as I can which is only about 4-5mm. Any more and I'll not be able to point it at the first mirror. I've also had the water pumping for a few hours and the bubbles are much reduced. They'll probably go completely given sufficient time but I think a bit more flow wouldn't go amiss so I've ordered a more powerful pump. If all else fails I'll also add a tiny bit of detergent to get rid of the tension in the bubbles.

    Time will tell!

  5. #5
    tap water or distilled?
    ========================================
    ELEVEN - rotary cutter tool machines
    FOUR - CO2 lasers
    THREE - fiber lasers
    ONE - vinyl cutter
    CASmate, Corel, Gravostyle


  6. #6
    Join Date
    Aug 2018
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    UK
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    Quote Originally Posted by Kev Williams View Post
    tap water or distilled?
    RO Water from the aquatics centre. Getting hold of distilled water turned out to be impractical due to shipping cost. Local tap water is really hard. De-ionised water seems to get the thumbs down from many so I avoided it. For anyone not knowing what RO Water is this is a paste from somewhere:

    "RO water is the result of the reverse osmosis process used for recycling, wastewater treatment and desalinisation. Used to remove contaminants from water by pushing it through a pressured, semi-permeable membrane, RO water can be used as a pure water supply in a number of industry sectors."

    Aquatics centres sell it for fish and it's really cheap.

  7. #7
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    Jul 2007
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    Yorktown, VA
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    Maybe I am missing something..

    Why tilted the tube? Why not leave it level and just put a temporary 3-4" high block under the entire laser housing on the outfeed side of the tube and just let the water run for a few minutes. The air bubble will move to that end of the tube and then out of the system.

    Most of our local groceries stores here carry distilled water in 1 gallon jugs for less than a dollar.

  8. #8
    RO water is mostly mineral free, large bubbles shouldn't hang around...

    It it were me, I'd take the air assist air line, stick it one of the tube's water hoses and let the air pump blow all the water out of the tube. Then I'd check on that bubble...

    As long as this has been going on, I'm thinking it might not even be an air bubble. Could be an anomaly of the glass forming process, and only looks like an air bubble.

    If it IS an air bubble, fighting fire with fire - or rather, air with air- will take care of it...
    ========================================
    ELEVEN - rotary cutter tool machines
    FOUR - CO2 lasers
    THREE - fiber lasers
    ONE - vinyl cutter
    CASmate, Corel, Gravostyle


  9. #9
    Join Date
    Aug 2018
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    UK
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    Quote Originally Posted by Rob Damon View Post
    Maybe I am missing something..

    Why tilted the tube? Why not leave it level and just put a temporary 3-4" high block under the entire laser housing on the outfeed side of the tube and just let the water run for a few minutes. The air bubble will move to that end of the tube and then out of the system.

    Most of our local groceries stores here carry distilled water in 1 gallon jugs for less than a dollar.

    I suspect one of the issues is the RO water itself. It's produced under pressure from the mains and as it's now sitting, the air dissolved within is gassing out, a bit like a glass of drinking water does. I have had the pump running now for a good number of hours and the bubbles have nearly cleared. I added a couple of drops of detergent and that helped a lot. I could have loosened one of the laser mounts and lifted one end of the laser but wanted a slight permenent slant as in the long term that's not going to be a bad thing. I haven't yet aligned the laser so moving it wouldn't have been an issue.

    I agree, you wouldn't have thought getting distilled water would be difficult. However, I tried everywhere locally and what they describe as distilled is actually deionised, and that's not the same at all. I could have bought it through Amazon or Ebay but 25litres including delivery was around 30 and that's a lot of your dollars! 25litres of RO water was 3 and only a mile away.

  10. #10
    Join Date
    Aug 2018
    Location
    UK
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    Hi Kev. It's a real bubbble all right. And actually many. But as mentioned just now, they have mostly gone now. I guess it's all a learning process. I do appreciate the feedback from you guys though.

  11. #11
    Join Date
    Jun 2011
    Location
    Camillus, NY
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    305
    I have "unlocked" the tube hold owns and tilted the tube and tapped with my finger
    It should flow away. Common problem in my limited experience.
    Jerry

    "It is better to fail in originality than succeed in imitation" - Herman Melville

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