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Thread: Some gears and testing for laser-ablating and -marking ...

  1. #121
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    ... actually assembling the DDL-module -- is it like "too big" for a diode-module ... or more like "tiny" for an air-cooled 400 Watt laser?

    Viktor
    Attached Thumbnails Attached Thumbnails DDL-Aufbau-Basis1.jpg  

    DDL-Aufbau-Basis2.jpg  

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  2. #122
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    Quote Originally Posted by VDX View Post
    And the focus is on the back-side, so even some dust on the surface won't burn in an crack it
    It appeared from the video that the glass wasn't very thick at all, which is why I was surprised that you could etch the back side while not making a mark on the front at all.

    Either the glass is much thicker than I imagined, or you have the power dialed in very precisely so that you're just at the point of etching on the back while the slightly defocused beam passing through the front isn't quite strong enough to do any damage.

    Either way though, very neat!

    Adam

  3. #123
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    ... the tiles are 8mm thick -- but even focussed on the top surface, the 1064nm with averaged 20W or pulsed with around 10kW and 200ns long pulses on a spot of 40 microns won't harm the (clean) glass ... but this is different, if coated/painted or heavy dusted.

    Attached are some more of the tiles - even the most "tinted" glass of them is perfectly transparent for the fiberlaser ...

    Viktor
    Attached Thumbnails Attached Thumbnails Glass-tiles-beamy.jpg  

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  4. #124
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    Quote Originally Posted by VDX View Post
    ... the tiles are 8mm thick -- but even focussed on the top surface, the 1064nm with averaged 20W or pulsed with around 10kW and 200ns long pulses on a spot of 40 microns won't harm the (clean) glass
    OK, now this is exactly what I had initially assumed - that the glass would be more or less perfectly transparent to the IR wavelength (even when focused) and thus you had to be etching a plated surface that was applied to the rear of the glass. But in your reply above you said that no, you were actually etching the glass directly by focusing the beam on the back of the glass only.

    I'm having difficulty believing that there's that much difference in the depth of field for your focal point between the top surface and the bottom surface, since they're only 8 mm apart and the laser source is easily 20 to 30 times further away... Because the only way you can etch perfectly clean glass using 1064 nm IR is with *very* high power and tight focus. With the distances involved, if you were using this method to etch the back surface (again, assuming perfectly clean glass), then the power density at just 8 mm away from the optimal focal point would still be high enough to do some etching on the front surface too.

    I don't know, maybe we have a language barrier in play here.?.

    but this is different, if coated/painted or heavy dusted
    Yes. This would be the "plating" or "coating" surface that I was referring to. Basically we're talking about a thin layer that is able to actually absorb the laser energy, unlike the clean glass.

    So once again: Are you actually etching the glass surface itself, or are you etching a coating that is applied to the rear surface of the glass that is then indirectly etching the glass as it is heated? (I fully realize that the explosive heating of an opaque coating will also etch the glass face it is touching as the coating layer is ablated.)

    Adam

  5. #125
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    Hi Adam,

    it's a bit of both - I'm engraving (etching?) the metallic coating on the back side, which, when heated up, will melt/etch the backside surface in contact too

    Did the same for marking/engraving the front glass surfaces of "deco-glass-diamonds" some time ago - here I've coated the surface with black paint end evaporated the paint with a blue 2W-laserdiode ... the hot plasma, while burning/evaporating the paint, melted the underlying glass surface ...

    Viktor


    *** EDIT ***
    - if you look on the second image with "VDX-LaserWORX" in post #120, then you can see some sort of "shiny bubbles", forming the chars -- here the pretty thin black (glass?) coating on the back side was burned away and while burning, let the glass "cook", so it melted and formed this "bubbles" ...
    Attached Thumbnails Attached Thumbnails Steine-Alle_kl.jpg  

    Stein-Detail_kl.jpg  

    Last edited by VDX; 05-10-2019 at 14:38.
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  6. #126
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    Quote Originally Posted by VDX View Post
    I'm engraving (etching?) the metallic coating on the back side, which, when heated up, will melt/etch the backside surface in contact too
    Right. That's what I had initially assumed. But your first reply seemed to claim that you were etching the glass directly, with no coating. That is what I couldn't believe. (Not because you can't etch glass with 1064 nm IR - you actually can. But if you had enough power to etch the back side, you'd also be etching the front at the same time.)

    We're on the same page now though. As the coating on the back side ablates, the glass it is in contact with is also etched.

    Adam

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