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Thread: jerky

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  1. #1

    Join Date
    Feb 2019
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    jerky

    Why does the machine work jerky? Before each line of the program there is such a jerk.

    TNG 2020.02.12

    Attached Files Attached Files

  2. #2
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    Re: jerky

    Your Z speed is limited. And because Z moves it sets maximum permissible speed.

  3. #3

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    Re: jerky

    The speed along the z axis is much lower than the limiting speed. I do not see the logic in such a limited.

  4. #4

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    Nov 2015
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    231

    Re: jerky

    You have set F to 2500 in the program. Your Z axis can only do F2000.
    I suspect that the machine brakes every time.
    Set program F2500 to F2000, also for X. Then the bucking should theoretically be over.

  5. #5

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    Re: jerky

    Yes, if you increase the speed limit it will work fine. But even if the z-axis is stationary, the machine will still twitch, this is wrong. I don’t know how the program algorithm works, but it’s wrong.

  6. #6
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    Re: jerky

    Try including a G64 command at the top of the program. If your machine defaults to G61, then you will get stuttering - check out the difference in the included gcode reference.

  7. #7
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    Re: jerky

    Actually, there might be a bug in the G61/G64 code because G64 seems to be ignored if you swap between these two gcodes.
    However, G64 does work straight after restarting TNG, but not after going to G61 and back again.

  8. #8
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    Re: jerky

    G64 expects P value to set tolerance. Without P tolerance set, it should default to value in settings. I'll fix this.

  9. #9

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    Re: jerky

    Quote Originally Posted by PlanetCNC View Post
    G64 expects P value to set tolerance.
    where is it set?

  10. #10
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    Re: jerky

    Just try something like G64 P1 and see how it performs.

    Check the Gcode manual the comes with TNG for more info.

  11. #11

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    Re: jerky

    Why does the machine jerk up and down?

    Attached Files Attached Files

  12. #12
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    Re: jerky

    You should try latest version.

  13. #13

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    Feb 2019
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    Re: jerky

    Nothing has changed. The machine works in jerks, and only at two points. You can watch the simulator yourself.

  14. #14
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    Re: jerky

    All issues mentioned in this thread were fixed in version 2020-06-18.
    I don't see any jerks in video. Where are they?
    If you are referring to speed decrease on top of circle it is because your machine can not change direction at set speed without breaking acceleration/deceleration limits. If you look closer at your g-code you'll see it is very rough at circle top.

  15. #15

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    Re: jerky

    I set the acceleration to 2000 and it still slows down. In these places, there cannot be such large accelerations, the trojectory is very smooth. It's not about acceleration.
    This happens very often(in places where the path consists of segments), the machine starts to decrease the speed where it is not necessary to do it. In artcam changed the accuracy from 0,1 to 0.01 and then nothing helps.

  16. #16
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    Re: jerky

    Trajectory is not smooth. It is very rough. In some places direction changes are huge. Direction changes causes accelerations/decelerations which exceed set limits. Larger blend values would normally help but not much in these short zig zag segments.
    Attached Thumbnails Attached Thumbnails Clipboard01.png  

  17. #17
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    Re: jerky

    Hello, Anriro! Privet, Brat!

    I can not see any errors in your code. I cannot find short zig zag segments too.
    I'm using "Basic CNC Viewer" for simulation view.
    Accuracy is not important - everything should work smoothly and with an accuracy of 1mm
    But you can try G64 P0.05 command here:
    ...
    G43 H1 G0Z40.0000
    M3 S18000
    G64 P0.05
    G0 Z20.0000
    X169.4222 Y651.9709
    G1 Z-0.2944 F1000
    ...

  18. #18
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    Re: jerky

    Anriro,

    Have you updated the software? The setting you posted indicated you are running 20200212. There have been 14 releases made that are newer than this. A lot of bug have been fixed in those as well as new features.

  19. #19
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    Re: jerky

    I have the same problem, I will not make a new thread if I will get answers here.
    The problem is because at any end of line machine will stop and then start again on new line. There is no settings at witch speed to move from one line to another.
    To manage this I lowered acceleration and jerky moves stopped, but that is not the solution, the machine stop moving at the end of line and start on new line.
    That also prolong execution of program unnecessary.
    It will be nice to have some settings to change feed rate by radius like flat 100%, radius 0.4mm 60%, radius 0.2 mm 40%, no radius (like an angle) 20%.
    There is BLEND in settings but I did not understand what is join angle and break angle, not explained in the manual.

  20. #20
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    Re: jerky

    I have similar peoblem at the begining, think the problem lies in pp from program generating g-code. Redone that in f360 solwe my problem.

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