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Thread: Laser Engraver DAC settings not fast enough

  1. #13
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    Default Re: Laser Engraver DAC settings not fast enough

    I just checked it again,

    If I make the 6th axis -1 it hits the desired feed rate, if I activate the 6th axis, it bounces around at about 80% of feed rate

    Thanks
    Dan

    Here is a screen shot of current settings.

    Attached Thumbnails Attached Thumbnails Laser Engraver DAC settings not fast enough-screen-shot-kmotioncnc-7-26-jpg  


  2. #14
    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Strange. What Version of KMotion are you using? Pleasepost a screen shot of your Tool Setup | Trajectory Planner Settings.

    Regards

    TK
    http://dynomotion.com


  3. #15
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    Default Re: Laser Engraver DAC settings not fast enough

    I think we are using one of the latest versions 4.33.

    Are there any other screen shots I can send you? Let me know.

    -Dan

    Attached Thumbnails Attached Thumbnails Laser Engraver DAC settings not fast enough-tool-set-1-jpg   Laser Engraver DAC settings not fast enough-tool-set-jpg   Laser Engraver DAC settings not fast enough-tool-setup-screen-jpg   Laser Engraver DAC settings not fast enough-version-4-33-png  



  4. #16
    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Yes we need the Tool Setup | Trajectory Planner Screen.

    Regards

    TK
    http://dynomotion.com


  5. #17
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    Default Re: Laser Engraver DAC settings not fast enough

    The screen shot from Post 13 or a different screen?



  6. #18
    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Thanks sorry I missed that. We were able to reproduce the problem. It is caused by your somewhat crazy Axis #7 motion profile settings. Very high Velocity=1e8 and relatively low Jerk=4e6.

    If you solve the fully Jerk limited motion equation:

    Velocity = 1/2 Jerk t^2

    you can see this would require 10 seconds to start/stop to maximum speed. KFLOP has a feature that monitors the amount of motion it has in its buffer and if it becomes significantly less than the time to stop all the axes defined in the coordinate system it begins slowing down the motion. With only an allowed Trajectory Planner Lookahead time of 3 seconds KFLOP always thinks the buffer is running dangerously low.

    Changing the Axis #7 Jerk value to a higher value (4e11) should solve the problem.

    HTH
    Regards

    Last edited by TomKerekes; 07-28-2016 at 04:01 PM. Reason: typo
    TK
    http://dynomotion.com


  7. #19
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    Default Re: Laser Engraver DAC settings not fast enough

    Thanks Tom,

    I just left town for a few weeks, next time i get a chance I'll revise the settings and report back.

    The support your team gives is amazing.

    -Dan



  8. #20
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Tom,

    We haven't forgotten about your video, we just haven't been able to get it to work quick enough to engrave anything legible.

    I'm not sure if lag in the chain is the KmotionCNC-Kanalog or Kanalog DAC-laser driver or the Laser driver itself. We have analog meters on order which will help to diagnose the signal at each step.

    But earlier on in post 4 you mentioned that there was a second possibility to control the Laser. You said:



    Quote Originally Posted by TomKerekes View Post
    Hi Dan,
    #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
    Do you have any examples of this in your C other programs I could see and understand it better? Everythign else has been working great.

    Thanks,
    Dan



  9. #21
    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    You could just add that in a loop. Such as:

    Code:
    for (;;)
    {
        WaitNextTimeSlice();
        DAC(7,ch7->Dest);
    }
    But I don't think that would make any difference. If you explain what configuration you are using and post some GCode we could take a look at it. If properly configured the X axis motion should be at the commanded feedrate and the analog output from Kanalog should settle to the commanded value within several hundred microseconds. If you do the math (200us x Velocity) would that explain something like you are seeing?

    At some point you mentioned 50ipm. At that speed the error would be 50/60ips x 200us = 0.2mils

    If the Laser itself has a time delay one trick I have used is to implement a digital delay of the Trajectory. By delaying the Trajectory, and not the Laser commands, the Laser commands then occur in advance of the position. You might consider that at some point. But it sounds like you have some more drastic issue if you can't even get a recognizable result.

    Regards

    TK
    http://dynomotion.com


  10. #22
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Tom,

    A little update on our trouble shooting status:

    We installed amp meters and volt meters and everything from the Kanalog out to the laser appears to be working properly.

    I started messing around with the settings in the KmotionCNC.

    Before with all of the advice you had given we had steady motion but little to no variation in the DAC output.

    I went into the Trajectory Planner Menu in KmotionCNC and changed the C Axis "Radius Inch" value from zero to different values (the box after the Degrees check box) and the DAC reading started to really jump around but we ran into the same issue as before where it's not a continuous motion in the X & Y (there is some slowing down) but the laser is going from high to low very quickly. The best setting is 0.1 for the Radius inch box that we have gotten to work there is still some slowing of the drive axis but we are getting an image that is recognizable. But about 1/4 way through the drawing the laser motion comes to a crawl.

    Is there something else that we didn't think about in the Trajectory settings which was causing the C Axis to drive very slow during coordinated motion?

    There will be a video headed your way when we finally get this ting working.
    Thanks Again
    Dan



  11. #23
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    Default Re: Laser Engraver DAC settings not fast enough

    Here is a test I made up for the attached image.

    Attached Files Attached Files


  12. #24
    Gold Member TomKerekes's Avatar
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    Default Re: Laser Engraver DAC settings not fast enough

    Hi Dan,

    Using Degrees with Zero Radius seems to work correctly for me.

    I Plotted your G Code as C (the desired Laser setting) vs Y Posiion for the first scan line:

    Laser Engraver DAC settings not fast enough-gcode-c-vs-y-png


    I ran the GCode and captured trajectory data in KFLOP for the first scan line. Here is the Y Position vs time. Note Y is at constant speed:

    Laser Engraver DAC settings not fast enough-y-position-vs-time-png


    Here is the C Position vs Time:

    Laser Engraver DAC settings not fast enough-c-position-vs-time-png



    Here is the Kanalog DAC Output captured on a Scope

    Laser Engraver DAC settings not fast enough-dac_voltage-png



    Here is the Trajectory Planner Settings that I used:
    Laser Engraver DAC settings not fast enough-tp_settings-jpg



    Here are the Configuration settings used for the C Axis
    Laser Engraver DAC settings not fast enough-config_settings-png



    Here are the Step Response settings used for the C Axis
    Laser Engraver DAC settings not fast enough-step_settings-png

    HTH
    Regards

    TK
    http://dynomotion.com


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