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  1. #1
    In the pursuit of madness I have just done another test on the milling table with the better quality laser, I did 6 runs each with different parts of the laser line some with the laser inverted, with the angle of incidence to the table random, etc. Again 10 stations over 500mm. Results are very consistent which makes me think there was something wrong with my last test.

    Click image for larger version. 

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    I don't think the laser mount is anywhere near stiff enough, it takes a few minutes for it to stop moving around on the screen to start a run and by the end of the run it has drifted by at least half the error of the run. Note that I haven't been testing with the laser on that desk rather out in the garage on a heavy bench over the bench leg.

    Click image for larger version. 

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    Click image for larger version. 

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    I think this laser needs to be clamped to a vblock attached to a lump of iron. It also has a focusing ring attached which works well other than it wobbles the laser all over the place. This might need to be locked in place as well.I have now gone from 'borrowing' the laser to owning it so it might well get some locktite on the focus slider.

    If anyone else wants one to play with they are sold here, £40.
    https://odicforce.com/epages/05c54fb...Products/OFL72
    Last edited by devmonkey; 10-01-2020 at 04:56 PM.

  2. #2
    Hi guys,


    I recieved my cheap webcam today.

    It is a ASHU H800 1080p cam, about 18 euro incl shipping.

    https://a.aliexpress.com/Zos0Tdull


    If internals are really 1920x1080 (windows says it is) this might be an ok device.

    The chip size is ~6.5mm x ~3.2mm


    So this sensor could be 0.003mm ish per pixel.

    I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


    Does the software account for not having the sensor 100% level?
    I hope it does.

    Or does not having it level actually help achieve sub pixel accuracy .

    The lens can be screwed out and put back on so it is only exposed to dust while in use.

    I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


    I will try to install the software and try icw the bosch laser i have.

    Will report back on progress.





    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  3. #3
    Quote Originally Posted by driftspin View Post
    Hi guys,


    I recieved my cheap webcam today.

    It is a ASHU H800 1080p cam, about 18 euro incl shipping.

    https://a.aliexpress.com/Zos0Tdull


    If internals are really 1920x1080 (windows says it is) this might be an ok device.

    The chip size is ~6.5mm x ~3.2mm


    So this sensor could be 0.003mm ish per pixel.

    I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


    Does the software account for not having the sensor 100% level?
    I hope it does.

    Or does not having it level actually help achieve sub pixel accuracy .

    The lens can be screwed out and put back on so it is only exposed to dust while in use.

    I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


    I will try to install the software and try icw the bosch laser i have.

    Will report back on progress.





    Verstuurd vanaf mijn SM-A320FL met Tapatalk
    Ok so i set 3um per pixel and got this result for a stationary setup.

    it looks like there is an upward trend... not sure what causes that yet.

    maybe the laser is heating up in the bosch auto levelling system moving it over time.


    This will be the best setup i can do so far to measure the flatness of the machine so far.

    Happy so far.


    Grtz. Bert

    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  4. #4
    Quote Originally Posted by driftspin View Post
    Hi guys,


    I recieved my cheap webcam today.

    It is a ASHU H800 1080p cam, about 18 euro incl shipping.

    https://a.aliexpress.com/Zos0Tdull


    If internals are really 1920x1080 (windows says it is) this might be an ok device.

    The chip size is ~6.5mm x ~3.2mm


    So this sensor could be 0.003mm ish per pixel.

    I wanted a bigger size sensor than the 640 pixel 2.5 mm one. Because of the width of the laser line on my bosch laser


    Does the software account for not having the sensor 100% level?
    I hope it does.

    Or does not having it level actually help achieve sub pixel accuracy .

    The lens can be screwed out and put back on so it is only exposed to dust while in use.

    I wil drill 2 mounting holes in the housing and bolt it to a piece of 4080 profile.


    I will try to install the software and try icw the bosch laser i have.

    Will report back on progress.





    Verstuurd vanaf mijn SM-A320FL met Tapatalk
    The app expects the sensor is in portrait orientation wrt the laser line, it then sums the intensity over each pixel row (sensor column) to produce an intensity curve which it post processes to determine the centre. This means if the laser line is at an angle to the sensor it doesn't matter, it should always find the height of maximum intensity at the centre of the sensor width. You don't want a crazy angle as it will reduce accuracy, a few degrees is fine though.

    I'm also going to move to a larger sensor, it takes too long to align the laser to the 2mm sensor over any reasonable distance.

  5. #5
    So I just tried it with a very nice cheap 1920x1080 camera from Amazon, sensor is perfect for our use, easy to rip apart and about 6mm of vertical resolution. However there is a problem, the library I'm using to connect to the camera only supports YUV format, which is a raw uncompressed image format. This means that over the USB connection higher def cameras cannot deliver the full frame rate of the camera because there is too much data to ship, I can only get 5 fps.

    I will have a look about for a different library, this would use MJPEG to compress the frames on the camera so they fit down the USB connection, that may in turn lead to other problems due to compression artifacts reducing the image accuracy, will have to see.

  6. #6
    Are you aware of this: https://openmv.io ?

    It is a single board computer with camera. You can develop machine vision algorithms in python or in C. They have different sensors but I am not sure they have one with a large enough area for what you desire.

    I can see how you would setup a single rail in a straight line with a laser/camera combination but don't understand how you would use a generated laser reference plane to setup a second rail.

    Dave.

  7. #7
    Quote Originally Posted by davebaldwin View Post
    I can see how you would setup a single rail in a straight line with a laser/camera combination but don't understand how you would use a generated laser reference plane to setup a second rail.
    Dave.
    Dave,
    Welcome to the forum (I see this is your first post). Make a nice hot cup of tea and read this thread from the start.

    Kit
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  8. #8
    Hi Dave,

    The laser line is a plane so you can either zero both rails to this plane or create a virtual plane from any 3 height measurements and zero to that.

  9. #9
    Joe,
    That's beginning to sound as fiddly as using the traditional West Systems 105/209 epoxy leveling method with more potential for errors. Gravity never makes mistakes. What do you see as the advantages to your proposed method?
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  10. #10
    Quote Originally Posted by Kitwn View Post
    Joe,
    That's beginning to sound as fiddly as using the traditional West Systems 105/209 epoxy leveling method with more potential for errors. Gravity never makes mistakes. What do you see as the advantages to your proposed method?
    Hi Kit,

    I do have a pack of 105/209 here for this machine, trouble is the temperature in the UK in my unheated uninsulated garage is about 6 degrees, so would have to wait until summer.

    I was also hoping we could improve upon the accuracy of epoxy, from the measurements taken in this thread:
    http://www.mycncuk.com/threads/8197-...5194#post65194
    and Jonathon's build here:
    http://www.mycncuk.com/threads/6484-...8616#post48616
    It appears with epoxy 60um (0.06mm) peak-peak error is possible, I think we can do better than this with the laser and also not have to wait 2 weeks for the epoxy to cure. It might be possible to perform the process I described above in a couple of hours. 0.06mm is 20 pixels on the image sensor to give an idea of comparable resolution.

    Cheers, Joe
    Last edited by devmonkey; 14-01-2020 at 09:57 AM.

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