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Thread: How to open a GSI Lumonics G120DT laser scanner?

  1. #11
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    Quote Originally Posted by absolom7691 View Post
    Again, sounds like a broken torsion spring. The "stages" you are feeling are the magnetic zero. The galvo will not work in those positions which is why you have to turn the shaft before the galvo starts working. I gave two of my old g120s away. If I still had any left over, I would have given it to you for the cost of shipping.
    in that case it makes sense.
    Also apparently the tension screws *didn't touch other one* was covered with some gunk and I see now its needs one of those tiny allen wrenches.
    I have one somewhere as I used it to fasten the gears of my 3D printers steppers. Thanks btw!

  2. #12
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    So I went down in basement and looked. Tested Stock =3 and I have a few mirror mounts. These do not have the notch in the shaft for the mirror. Your amps are flexible enough to deal with this.

    If you loosen the set screw, remember, you have to recalibrate zero using a bench laser, a clamping hemostat, to hold the shaft, an oscilloscope etc... Placing an uncalibrated rebuild into drive will damage something for sure. There are portions of the rotor milled to 10 micron tolerances. Those portions form the grounded plate of four air variable capacitors in the position sensor. The capacitance change is very small, on the order of femtofarads per image point. To sense that small a change, they use a very high frequency, high voltage to excite the capacitance bridge.

    The "gunk" is usually red potting compound. Used to prevent tampering on defense electronics. Red is the soft version, and that comes out with a tiny drill bit and a pick tool.
    When you drill it, you must not damage the head of the Allen screw. This means drilling by hand using a pin-vise.

    Run the "AA" battery tests, too.

    Steve
    Last edited by mixedgas; 10-22-2014 at 05:39.
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  3. #13
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    See attached quotes from GSI Inc manual "User Manual Galvanometer Scanners". No copyright date is shown.
    Attached Thumbnails Attached Thumbnails GSI-structure1.jpeg  

    GSI-structure2.jpeg.jpeg  

    GSI-structure3.jpeg.jpeg  

    GSI-structure4.jpeg.jpeg  

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  4. #14
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    Quote Originally Posted by mixedgas View Post

    Final edit:

    I viewed video two. Please NEVER run a tuned G120 amp without the mirror mass on the galvo, IT will most likely oscillate unstably..... this leads to broken torsion bars. OUCH!

    Its OK, you didn't know about the old ways...

    Steve
    eek! that might have been the cause then :/ lesson learned!
    I will glue a mirror to it before I continue testing it further.
    Then I will do the DC battery test

    The previous mirrors were epoxied and broken I removed them with a temperature controlled soldering iron and clamped something around the shaft to hold it and dissipate the heat. I was able to pull it off super quick so the shaft didn't get hot and would not cook out any oils out of the bearings.

    I'm calling HB-laser today to see if I can get this information or hit up Ben on facebook.

    I'll try to do the other tests soon.

    If you want more information about the amps (primairly pictures for now) Just ask and I will try to obtain that.
    It also has marked test points sticking out of the board and clearly nobody has messed with it as it still has it's warranty stickers on it that aren't broken.

    Thanks for the documents btw.
    Last edited by masterpj; 10-22-2014 at 07:47. Reason: grammar

  5. #15
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    Sorry been buzy with studies and work but I'm back!
    I got the scanner amplifier manual from HB-laser and I think I should share it since a lot hadn't seemed to have seen this amplifier before.
    https://dl.dropboxusercontent.com/u/...lo_prof4_e.pdf

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    So I got the scanners to scan properly though only at small angles. I did some tuning and had made my scanner mirror for one axis by cutting a bathroom mirror by hand in a very small square piece in a similar size to the other axis mirror.

    I stripped the paint to make it a front surface mirror and glued it on.

    It works and is not making any squeeling sounds anymore.

    This scanner amp is amazing despite the thick mirrors it allows the G120DT's to run at almost 30kpps at an decent angle! Corners are really nice and sharp.
    I think with a better mirror attached to the X-axis I can scan even higher!
    Click image for larger version. 

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    Edit: now scanning fine at 30kpps
    Click image for larger version. 

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    Last edited by masterpj; 11-08-2014 at 05:21.

  7. #17
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    PJ, at 30K G120 is a eight degree scanner. Your just fine.

    Steve
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  8. #18
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    Quote Originally Posted by mixedgas View Post
    PJ, at 30K G120 is a eight degree scanner. Your just fine.

    Steve
    One thing is that its a bit wobbly in the X-axis when sized up quite a bit. I notice when moving up and down in the Y-axis away from the center all is fine but in the X-axis I get wobble.

    My assumption is that either the mirror is not properly mounted or the mirror is too heavy.
    I will redo it and I wil hunt down a proper mirror for it.
    I might salvage one from a cheap scanset I have laying around.

    I also need to help it get out of one of the 0 points before turning it on so it can move but otherwise it works perfectly.

  9. #19
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    Might be time for a new scanner, because of either the bearings or a torsion bar issue.
    I still have a few I can part with.

    Steve
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  10. #20
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    how much would you ask for one?
    I would need to save for a while along that pcaom crystal I am buying from dsli because since I'm studying fulltime I cannot take as much work as I would want to

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