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Answered Don't print on bare glass

Discussion in 'Troubleshooting' started by Bd182, Mar 7, 2019.

  1. Bd182

    Bd182 Member

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    I started printing on the bare glass bed because I was worried that the hairspray may have clogged my nozzle. It works great. Moderately sized parts stick really well while the bed is hot, and when it's cold, they fall right off.

    But I began to see fractures within the glass. It's not chips being pulled off by prying up a hot print. The glass is just fracturing and staying in place. I think it's because the print sticks SO WELL to the glass that it pulls the borosilicate glass apart as it cools and shrinks.

    I'm going back to hairspray, but not to get better adhesion. I'm using it to get LESS adhesion.
     
  2. BrooklynBay

    BrooklynBay Active Member

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    I've been using a sheet of high temperature glass from a door of an old broken toaster oven for a few months with good results. It was an exact fit (10" X 15"). I've read that some people have been using plain glass, and they have good results. I'm surprised that the regular glass is able to hold up with all of the heating & cooling cycles.
     
  3. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Since the heating and cooling cycles are not extreme regular old float glass works and is way cheaper than a piece of borosilicate glass. An added benefit for float glass is that when it fails it breaks instead of pulling out chunks / chips from the glass surface (more common than most people think). Plus it is easy to find float glass anywhere.
     
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  4. Bd182

    Bd182 Member

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    I laid a sheet of single strength window glass over my bed and it seems to work fine. Robo suggested a sheet of PEI. Is that a step up?
     
  5. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    I am not a fan of PEI sheets and would rather use Window / Picture Pane (float glass) with either cheap hair spray or glue stick to increase adhesion for certain materials.
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep, your call. Be warned that sometimes, some materials will stick TOO well with things like PEI.
     
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  7. Bd182

    Bd182 Member

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    Everyone tells me something different! ;-)

    Anyway, my window glass has been fine for the last several prints. One begins to wonder why the makers tout borosilicate glass when it seems to have specific flaws. Like fracturing. Heated beds are gradual and no threat to float glass. I suppose float glass is more likely to break if you drop pliers on it. Is that the reason they use borosilicate?
     
  8. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Borosilicate is a bit tougher but wholly unnecessary.
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Honestly ... I can't reverse engineer their logic :)
    Borosilicate was originally used for lab glassware where it would tolerate sudden excursions of temperature high-to-low and vice-versa without shattering. Baking in an oven or autoclave, etc. Even then it was used to hold primarily liquids.

    The glass bed on a printer never meets those sort of requirements. It does get (just) hot enough to qualify, but it gets there slow and steady (same for cooling off).

    Given how Boro--- screw it-- PYREX fails by flaking or chipping it is "safer" but the fact that it will do that easily is not really ideal for how a printer bed is used. You are deliberately getting materials to "adhere" to it and then pulling them off.

    So in the summary :) You don't need it. Float glass works fine for use as a top layer and unless you are a gorilla or have an accident that glass will hold up fine and if it does fail you can replace it pretty cheap.
     
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