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Multiple small step G1 results in no laser output

Discussion in 'General Talk' started by O G, Jul 10, 2020.

  1. O G

    O G New
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    I have a job generated by OpenBuilds CAM that contains many G1 instructions back to back that each take a very small increment. The problem is when I run the job my laser slowly moves along the expected path but the laser is rarely on. I can't find the mistake in the gcode. Is there a limit to how small you can move with G1?


    sample from the begining.

    G0 Z0
    G1 F300 Z-0.1000
    G1 F1000 X13.5583 Y57.7621 Z-0.1000 S1000
    G1 F1000 X13.5539 Y57.7577 Z-0.1000 S1000
    G1 F1000 X13.5493 Y57.7533 Z-0.1000 S1000
    G1 F1000 X13.5448 Y57.7489 Z-0.1000 S1000
    G1 F1000 X13.5403 Y57.7444 Z-0.1000 S1000
    G1 F1000 X13.5358 Y57.7400 Z-0.1000 S1000
    G1 F1000 X13.5313 Y57.7356 Z-0.1000 S1000
    G1 F1000 X13.5268 Y57.7312 Z-0.1000 S1000
    G1 F1000 X13.5223 Y57.7268 Z-0.1000 S1000
    G1 F1000 X13.5177 Y57.7223 Z-0.1000 S1000
    G1 F1000 X13.5132 Y57.7179 Z-0.1000 S1000
    G1 F1000 X13.5087 Y57.7135 Z-0.1000 S1000
    G1 F1000 X13.5042 Y57.7091 Z-0.1000 S1000
    G1 F1000 X13.4997 Y57.7047 Z-0.1000 S1000
     
    #1 O G, Jul 10, 2020
    Last edited by a moderator: Jul 10, 2020
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    Did you remember to set $32=1? Refer github.com/gnea/grbl/wiki > Laser Mode
     
  3. O G

    O G New
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    I double checked, yes.

    I've been cutting fashion patterns for almost a year with this setup. It's just that one small increment job that doesn't work :hmm:
     
  4. O G

    O G New
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    Ok so what I did next is programatically generate jobs that moved smaller and smaller increments. When I could move 0.0001 step without triggering that problem I figured the step distance wasn't the problem. The problem, as it turns out. Is my setup doesn't like M3+M4, prefers solo m3, I don't know why but if anyone can explain that would be awesome. Also too bad that OpenBuilds CAM forces an M4 instruction.
     
    #4 O G, Jul 10, 2020
    Last edited: Jul 10, 2020
  5. Rob Taylor

    Rob Taylor Veteran
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    gnea/grbl

    In laser mode, output power is dynamic under M4. Short moves are primarily acceleration and deceleration, which means that the laser won't be on much at the commanded power. Override power level, re-CAD properly with arcs instead of lines, or turn off laser mode (and make sure your post processor doesn't assume grbl will turn off the laser for rapids). Or just find-and-replace all M4s to M3s.
     
    Peter Van Der Walt likes this.
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    It does not :) , it suggests M4.. but you can select any initialization sequence you like from the Tool Initialization dropdown - Constant power has always been an option in the list

    upload_2020-7-10_17-43-57.png

    Furthermore if you dislike the predefined options there, you can refine it even further by going to Step 5 "From your machine and controller choice above we have prepopulated the settings below. If you have any custom requirements, please customise the settings below"

    From where you can edit the start GCODE (and others) to include any commands you like, you can even tweak the commands used, etc to fit other firmwares etc if you know what it needs

    upload_2020-7-10_17-45-3.png
     
    #6 Peter Van Der Walt, Jul 10, 2020
    Last edited: Jul 10, 2020

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