Need Help! Laser Engraver DAC settings not fast enough


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Thread: Laser Engraver DAC settings not fast enough

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    Default Laser Engraver DAC settings not fast enough

    I have set up a Laser diode on to the my cnc machine that is using DAC 6 on Kanalog to send the 0-5 volts required for the laser driver's intensity to vary laser power for burning grey scale images into material.

    The G code that the photo engraving program spits out has a X & Y & Spindle Speed S combo for every 0.006" as that is the resolution of the image and laser spot size. The machine should be travelling at 50 Inch per minute as it burns the image but it never reaches above 3 IPM as i think it's due to the velocity/acceleration settings of the DAC slowing the whole machine down. I also set up a laser engraving file to print with constant S intensity and instead vary the speed of X & Y and it ran that file as the appropriate speed. So this is what is leading me towards to DAC 6 not being set up properly. I tried to increase V and A and J but it didn't seem to help matters.


    What settings should I be using in my configuration file to make it sufficiently fast enough to not be the slowest point of the coordinated motion?Thanks for the help as always.
    I've attached my initialization file or reference.

    Thanks for the help
    -Dan

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    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    The S Spindle Speed Command isn't designed to work at high speed and to be synchronized with the motion. The Interpreter flushes the look ahead and so forth when it encounters an S command. So I don't think it will ever work in the way you are intending.

    Would it be ok to use an additional axis as a "dummy" axis that could be used to control the intensity instead? If so an angular axis might be the best choice as it shouldn't effect the feedrate calcs of the xy motion at all. KFLOP could then output the dummy axis position to the DAC.

    Regards
    TK

    TK
    http://dynomotion.com


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    Default Re: Laser Engraver DAC settings not fast enough

    Quote Originally Posted by TomKerekes View Post
    Hi Dan,

    Would it be ok to use an additional axis as a "dummy" axis that could be used to control the intensity instead? If so an angular axis might be the best choice as it shouldn't effect the feedrate calcs of the xy motion at all. KFLOP could then output the dummy axis position to the DAC.

    Regards
    TK
    Ok thanks Tom I will give that a try.

    One question, how can I limit DAC Output to not go above 5V? I could do so with the Spindle C-code in my other way. Somehow I have to set the DAC to be able to drive twice as fast as I ever plan to go and just never set the speed above the half way point? What parameter do I set for this? Is it still Max Velocity in the Motion profile screen?



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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    I'd suggest an approach like this:

    Configure an Angular axis (ie th A Axis) and command it in G Code from 0 to 1 degree to correspond to power 0V to 5V.

    Configure the A Axis as 1024 counts/degree. and to be very fast Vel = 1000 degrees/sec and Acceleration = 1000000 deg/sec^2

    A=1deg should then command the axis Dest to be 1024 counts

    Then to output to the DAC I can think of 2 possibilities:

    #1 - Treat it as a DAC Servo with the Feedback stuck at zero

    Configure DAC Servo with No Input (Position always zero)

    MaxError = 1024, Max Output = 1024, gains P=1 I=0 D=0 No Filters No FF

    Therefore with a Destination of 1024 and the Position=0 the error will be 1024 and with a P gain of 1 the output to the DAC should be 1024 or 5V

    #2 - use a User Program and a forever loop to output the Dummy Axis Dest to a DAC with something like:

    DAC(6,ch6->Dest);

    Using a user program could also allow for safety checks. Maybe use a table/equation to correct for non-linearities, etc...

    HTH
    Regards

    TK
    http://dynomotion.com


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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Tom,
    I set it up as you suggested with Option 1, making the Laser the C axis command and setting up Channel 7 as a DAC Servo.

    I can get the laser to function and vary voltage from 0-5 going from 0 to 1 deg, but the speed is still just as slow.

    I've attached my revised Initialization file for reference.

    Am I missing something?

    Thanks,
    Dan

    Attached Thumbnails Attached Thumbnails Laser Engraver DAC settings not fast enough-screen-shot-kmotioncnc-jpg  
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Try setting the Trajectory Planner C Axis Radius to Zero.

    Regards

    TK
    http://dynomotion.com


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    Default Re: Laser Engraver DAC settings not fast enough

    Where is that? The Break Angle input?



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    Default Re: Laser Engraver DAC settings not fast enough

    Found it, It works!

    Thanks so much!!!!!



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    Default Re: Laser Engraver DAC settings not fast enough

    Can't wait for the Video

    TK
    http://dynomotion.com


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    Default Re: Laser Engraver DAC settings not fast enough

    We will definitely put something together once it's working well. There doesn't seem to be enough time come the summer.....


    One issue that popped up and didn't narrow down until today was that once we added the C axis to the initialisation file the coordinated motion for X,Y,Z won't move beyond 80 IPM. But the Rapids will move up to 380 which is normal. I thought the issue was in the KmotionCNC settings as all the documentation suggests, but noting made a difference. The Feed override wouldn't help get it above 80 IPM. (and this is while using the spindle regularly.)

    When I went into the initialisation file and removed the C axis the machine started reaching what ever feed rate I input.

    I changed DefineCoordSystem6(0,1,2,-1,-1,7); to DefineCoordSystem6(0,1,2,-1,-1,-1);

    I'm wondering what in my initialisation for Channel 7 is limited the rest of the coordinated motion?

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    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Are you moving C in the GCode when the feed rate is limited?

    What are your Tool Setup | Trajectory Planner | Axis Parameters | settings for C?

    Regards

    TK
    http://dynomotion.com


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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Tom,

    No C command, just a simple tool path with the spindle, movement in x and y direction. Nit even diagonal moves, just x then y and it won't go the desired feed rate .



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Laser Engraver DAC settings not fast enough
Laser Engraver DAC settings not fast enough