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Thread: advice on scanner mirror thickness needed

  1. #1

    Default advice on scanner mirror thickness needed

    Can I use the same 1mm thickness for bigger mirrors? I need to make some big ones for 1cm aperture, not sure if 1mm will be stiff enough. The next available thickness in the list is 1.9mm.

    Also a side question, how to go around cutting thin mirrors?
    I have a glass cutter but the pressure might shatter it. I also have a dremel tool.

  2. #2
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    We offer mirrors that will move a 10mm beam, that are only 1.1mm thick, made of glass, work pretty well
    Sincerely,
    Ryan Smith
    ScannerMAX Mechanical Engineer
    ryan {at} scannermax.com

  3. #3

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    Thanks for the info. What would you use to cut them? (besides very high power laser CNC cutter)

  4. #4
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    honestly not sure. i just send drawings to manufacturers and they make them.not sure how well scoring and breaking would work.

    how many sets do you need? we have 10mm aperture 1.1mm thick mirrors in stock and might just be worth it to buy a set at a very reasonable cost...

    Attached a photo below of the general concept

    10mm.PNG
    Sincerely,
    Ryan Smith
    ScannerMAX Mechanical Engineer
    ryan {at} scannermax.com

  5. #5

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    I want to make some myself, since this is for experimenting with different sized mirrors I rather get a sheet and cut some sizes from that instead. Was about to get few thick sheets of glass for knife edging anyway so I can just add one more thin mirror sheet to my order.

    Anyone else want to chime in about how to go around cutting these?

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    There are a number of threads on here, I was looking for the same information a few months ago and found it without too much difficulty.
    Long and short of it was use a diamond tipped glass cutter, dipped in light oil, scribe once only. I'm planning to use an ex-Polaroid camera mirror as they're easy to get, thin, and large 1st surface mirrors.
    Last edited by NobleGas; 08-17-2016 at 11:41.

  7. #7
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    In the production world, blanks are cut, edged, and then coated. Going backwards, ie coated, cut, edging, results in damaged coatings.
    !
    Usually the blanks are cut using a diamond impregnated wet blade (diamond saw or lapidary saw) and then coated.
    One of my friends, a PLer, has a wet, diamond bladed, lapidary bandsaw for this, but he sticks to much larger mirrors.
    It is cheaper for a laser hobbyist to buy a large mirror and cut it, until you get down to galvo mirror sizes, then its expensive because you break it.
    The 5" diamond bladed saws with water cooling start at 2000$ each.. Blades are about 10-30$ each.
    If you had a lathe, you can make an arbor and use a lathe to hold the diamond wheel. They spin at just a few rpm to a few tens of rpm and are quite tame for handwork.
    !
    If the glass is annealed the right way, for thin blanks a robotic diamond scribe is used. After the blanks are scribed
    they are manually broke along the scribe lines with a very high loss rate.
    !
    One of my college jobs was breaking the machine scribed glass in a LCD display plant, then coating it. Our losses were huge.
    !
    Now for the down side, you have zero control over the annealing state when you buy a stock coated mirror. Sometimes I get stock that is annealed correctly for cutting and dicing. Other times... Well, its shatter city.. Its not something vendors care about, unless your ordering a huge amount of custom mirrors.
    !
    Other lens and mirror blanks are ground to shape prior to cutting, using a silicon carbide or diamond wheel, and in some cases a diamond tipped lathe.
    We do some course and fine hand grinding at work using special belt sander belts made for glasswork.
    !
    Generally cutting after coating leaves a very messed up optical edge. Often the coating will flake, depending on its adherence. Mil Spec coatings are tested for this, civilian dielectrics are not...
    !
    I used to cut my own pre-coated stock for G120 mirrors, which while thin, (0.7 mm) are much larger and easier to handle then modern mirrors. My loss rate was high. That glass vendor is out of business, too. I used a diamond tipped scribe and a ruler, plus glycerin to fill the scratch and aid in breaking. Breaking must be done right after scribing, or the cut starts to "heal" and will not break as clean. In other words, break within a minute of scribing, don't let it set for hours.
    !
    Good Luck,
    !
    Steve
    Last edited by mixedgas; 08-17-2016 at 11:57.
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  8. #8

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    Quote Originally Posted by mixedgas View Post
    In the production world, blanks are cut, edged, and then coated. Going backwards, ie coated, cut, edging, results in damaged coatings.
    because of the glass an aluminum dust scratching the mirror, or do you mean the coating around the edges?
    If you mean the former, why not remove the protective film afterwards?

  9. #9
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    Quote Originally Posted by syrah View Post
    because of the glass an aluminum dust scratching the mirror, or do you mean the coating around the edges?
    If you mean the former, why not remove the protective film afterwards?
    The protective film slides on the glass when the shockwaves from cutting the glass break and micro-fracture the edges of the cut.
    It does nothing to help protect the multilayer dielectric coating which will chip, crack, and flake at the cut, and sometimes beyond.

    Think major earthquake in the glass, like San Andreas fault. Which is how the glass splits.

    Steve
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  10. #10

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    I see. Are you talking about visible damage or microscopic? I can make power measurements after I get the mirror and cut it, if anyone's curious.

  11. #11
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    It will do both micro and macro,
    Depends on the glass, its annealing state, and how its scribed. In other words, the Wild Wild West.

    Steve
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  12. #12

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    I see. Good thing I have a LPM now.

    Another related question I have. I need to make few 15mm x 15mm mirrors for beam steering. Should I go with 6mm or will 3mm be stiff enough?

  13. #13
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    It's not really an issue of stiff enough (beyond just ridiculouy thin...) as much as flat enough. (And is there so much power density that you need to worry about thermal effects.) With narrow beams flat enough is pretty easy, but as the beam diameter goes up so does the effect a lousy mirror has on beam quality at a distance)
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  14. #14

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    These mirrors are sold by firstsurfacemirrors.com. They are 1λ mirrors. That should be good enough right? Flatter ones are only available in 6mm thickness and 25mm x 25mm sizes.

  15. #15

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    What would you use to cut them?

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