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Thread: CNC Laser Engraving 8bit Shades of Grey 445nm

  1. #1
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    Laser Warning CNC Laser Engraving 8bit Shades of Grey 445nm

    Hi everyone,

    I'm new here and I hope this is the right place to post this. I would like to introduce to everyone a new process me and my son developed to laser engrave 8bit shades of grey using a 1W 445nm laser diode on our CNC router. There is no dithering a image first, no pulsing or overlapping dots to get the allusion of shades. What we have developed is a way to vary the laser diodes intensity by analog modulating the laser diode to get 8bit greyscale. The driver we are using is drlava's Flexmod P3. With our setup, we can just use a standard X,Y and Z g-code from any image to g-code rotary engraving type of program for this process. We use Artsoft's Mach3 CNC controller program to run the gcodes. No special laser engraving software or program is required, but we prefer to use PicEngrave Pro 4 Plus Laser which have been written with specific enhancements for this process.

    Using a laser diode compared to a CO2 to do these engraving is a very slow process, but the results are very gratifying/rewarding for us. This is just our hobby so time to produce them is irrelevant. We have successfully engraved on wood, artist canvas and mirrors with stunning results. With our setup, we can also use Constant Wattage and vary the feedrate to get shades of grey, or use TTL to pulse the laser with a dithered black and white image.

    The smallest burn line we are able to achieve is .007" because of the 3 element glass lens we are using now. Does anyone know of a source of any optics with the 9X.5mm thread that can focus down any smaller then what we are getting now? We are looking into improving the detail and sharpness of our engravings that can be achieved.

    Here is an example of our analog modulation engraving process being used on Birch Plywood.

    Jeff
    Attached Thumbnails Attached Thumbnails BigCat.jpg  

    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

  2. #2
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    Wow that is awesome man!
    Great work i would love to build a setup like that.
    Do you have any more pics ?
    When God said “Let there be light” he surely must have meant perfectly coherent light.

  3. #3
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    Thank you,

    Here is a couple more of my past engravings. The first one is using Constant Wattage with variable feedrate and the second is using analog modulation. The variable feedrate one is a little darker, but could have been corrected by speeding up the feedrate some more. I prefer to use analog modulation because it's not as hard on the laser diode by running at full intensity for long periods of time like with variable feedrate. The advantage of variable feedrate, it only requires a TTL modulation driver. Picengrave Pro 4 Plus Laser has settings for both processes, plus TTL dithering/pulsed B&W images and rotary image engraving also. It's one complete package including image editing tools.

    Here is the image to gcode program I'm using. http://www.picengrave.com/

    Jeff
    Attached Thumbnails Attached Thumbnails 1var.jpg  

    2an.jpg  

    Last edited by JJWMACHINECO; 02-20-2014 at 12:36.
    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

  4. #4
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    Hi,

    I don't know anything about wood engraving, so this might be a stupid question, but how do you produce those shades that are lighter than the wood colour itself?!

    Also, how long does it take to produce such an image? They look very nice!

  5. #5
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    swamidog is online now Jr. Woodchuckington Janitor III, Esq.
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    have you considered using 405nm diodes? the beam specs are better and you may be able to focus to a smaller point due to the shorter wavelength.

    your post is well timed. i've been speccing out xy stages at lightobject.com

    please post more information and pics/video of your system.

    thanks!

    Quote Originally Posted by JJWMACHINECO View Post
    Hi everyone,

    I'm new here and I hope this is the right place to post this. I would like to introduce to everyone a new process me and my son developed to laser engrave 8bit shades of grey using a 1W 445nm laser diode on our CNC router. There is no dithering a image first, no pulsing or overlapping dots to get the allusion of shades. What we have developed is a way to vary the laser diodes intensity by analog modulating the laser diode to get 8bit greyscale. The driver we are using is drlava's Flexmod P3. With our setup, we can just use a standard X,Y and Z g-code from any image to g-code rotary engraving type of program for this process. We use Artsoft's Mach3 CNC controller program to run the gcodes. No special laser engraving software or program is required, but we prefer to use PicEngrave Pro 4 Plus Laser which have been written with specific enhancements for this process.

    Using a laser diode compared to a CO2 to do these engraving is a very slow process, but the results are very gratifying/rewarding for us. This is just our hobby so time to produce them is irrelevant. We have successfully engraved on wood, artist canvas and mirrors with stunning results. With our setup, we can also use Constant Wattage and vary the feedrate to get shades of grey, or use TTL to pulse the laser with a dithered black and white image.

    The smallest burn line we are able to achieve is .007" because of the 3 element glass lens we are using now. Does anyone know of a source of any optics with the 9X.5mm thread that can focus down any smaller then what we are getting now? We are looking into improving the detail and sharpness of our engravings that can be achieved.

    Here is an example of our analog modulation engraving process being used on Birch Plywood.

    Jeff
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by colouredmirrorball View Post
    Hi,

    I don't know anything about wood engraving, so this might be a stupid question, but how do you produce those shades that are lighter than the wood colour itself?!

    Also, how long does it take to produce such an image? They look very nice!
    Quote Originally Posted by swamidog View Post
    have you considered using 405nm diodes? the beam specs are better and you may be able to focus to a smaller point due to the shorter wavelength.

    your post is well timed. i've been speccing out xy stages at lightobject.com

    please post more information and pics/video of your system.

    thanks!
    Thank you,

    To answer both of your questions, the last two engravings are 7.5” X 9.5” and running with a stepover of .007” at 50IPM and took about 3 hours and 15 minutes to engrave. I’m in process on another build with dual 2.5W 445nm diodes that will speed the engraving process up considerably. Your correct, it’s not really shades of grey because of the color of the Birch Ply, but with my setup I have 256 levels of power from wood color to burnt dark. I use a US Digital MA3 10bit analog shaft encoder that outputs 0-5V for the analog modulation to the driver in a 360 degree rotation. In my image to gcode program, it interprets the image into 256 .0001” Z axis moves (depths of cut) which my encoder is tied by a timing belt to the Z axis.

    There is another electronic means using a DAC that takes the step and direction pins from Mach3 to get the 256 steps (power levels) also. Here is a PDF that was written by the author of the program I use and explains in more detail how it is done. More information about my setup is in this PDF also.

    http://picengrave.com/Laser%20Setups.pdf

    John, the author of Picengrave Pro is in process of building a laser diode engraver using an X&Y stage from lightobject.com. He will be using a Max5451 digital potentiometer for the 256 power levels. His program lets you select A,B,C or Z axis for the Gcode generation to control the laser diode's power levels.

    I have looked at a 405nm, but what I have read, the 445nm's have more wattage and durability. My laser diode engraver mounted on a CNC router has over 800 hours on it with no failures.

    Here is a video of my mini laser engraver in action. If you watch the 0-5V analog volt meter, the voltage goes up and down with the power of the laser diode.

    Jeff

    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

  7. #7
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    The 405 nm wavelength will interact more strongly, but operates at lower power and so this might be close to an even trade off. However, I believe these diodes are single mode and therefore with the right optics will be able to produce a much smaller focal spot size. The trick to a smaller spot assuming optics of the same, reasonable quality is a shorter focal length. You could insert a positive lens after the current collimator and with a choice that cuts the distance from this new lens to the focus to 1/2 the spot size will similarly decrease to 1/2 the diameter. There are a number of other ways to accomplish this, but the concept is the same. The steeper the light comes in to the focus the smaller the spot.

  8. #8
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    Thank you for the information. I have some different lenses around here to experiment with. Right now I'm using this 3 element glass lens with the AR coating.

    http://www.ebay.com/itm/3-Pack-445nm...item2a20b16c49

    Jeff
    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

  9. #9
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    this would be a good choice of 405nm diodes to experiment with:

    https://sites.google.com/site/dtrlpf...12x-405-diodes

    (cribbed from laserpointerforums)

    Vf------mA----mW
    4.01----50-----38
    4.35----75-----81
    4.62----100---121
    4.88----125---166
    5.08----150---209
    5.27----175---255
    5.41----200---296
    5.53----225---337
    5.64----250---381
    5.73----275---418
    5.81----300---462
    5.88----325---503
    5.93----350---537
    5.99----375---579
    6.04----400---617
    6.08----425---656
    6.11----450---692
    6.15----475---728
    6.18----500---767

    i think i would shoot for ~450mA initially.

    c.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  10. #10
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    Thank you for that information, but I have already invested way to much with DTR on 445nm diodes and lenses already to change directions now. I have not seen or know of anyone using a 405nm to laser engrave photographs, but there are several I know of that do use the 445nm. I'm going to try experimenting with the optics first.

    Jeff
    Extensively Re-worked/Re-designed/Modified Servo K2CNC KG-3925, Mini Diode Laser Engraver and now a Shapeoko 2 Laser Diode Engraver.

    https://www.picengrave.com

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