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Fusion360 - OpenBuilds Post Processor vs. Generic Grbl

Discussion in 'CAM' started by Holley, Aug 5, 2021.

  1. Holley

    Holley New
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    I ran the same toolpath and compared processors, OpenBuilds vs Generic Grbl

    I set XYZ at corner of the stock.

    The OpenBuilds Post processor starts with a Z-10 dives into stock, then moves X,Y!

    Attached Gcode for same toolpath
     

    Attached Files:

    • OBPP.gcode
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    • G.nc
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  2. Alex Chambers

    Alex Chambers Master
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    Do you have limit switches and are you homing the machine on start up? I'm assuming you have a grbl controller like the blackbox? The first move with the Openbuilds post processor is a safety move - if Z home is 0 then that G53 (machine co-ordinates not workplace co-ordinates) Z-10 move lifts Z to 10 mm below the home position. When you home Z does it home at the top of it's travel?
    Alex.
     
  3. Holley

    Holley New
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    Black box, Interface controller, limit switches.
    Ok. I’ll try and “home” the Z to it’s limit
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    No, its G53 .... Z-10

    G53 Z-10 is 10mm below you homing limit switch at the top of your Z axis.

    It is NOT a Z-10 move

    1) home correctly
    2) G53 moves are clearance moves in machine coordinates
    3) Stock is set in G54 (Work coordinates) using probes and zeroing

    Reiterating:
    G53 = machine coordinates = only set by homing
    G54 (and G54-59.1) are work coordinates = can be set using zeroing and other commands
    Work coordinates are offsets from machine coordinates
    Machine can move in Machine and Work coordinates - what matters is which G53/54-59.1 system the move is in)
     
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    @Holley you have not replied to my request for more information about your query about drilling holes in Fusion. I created a few hole drilling ops and could not find any problems with the Gcode the OB postprocessor produces so if you still have a problem with drilling I need your fusion file and gcode file (only from OB post, the stock GRBL post is broken ,don't use it) so I can debug it.
     
  6. Holley

    Holley New
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    It wasn’t the toolpath and processor, it was homing. The Z axis started with a Z-10

    I homed the machine and it is fixed.
     
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  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Always home on startup. Every other coordinate system is just an offset from Machine Coordinates so establishing MPos by homing first is critical.
     
    David the swarfer likes this.
  8. Holley

    Holley New
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    So...Z homed correctly. Then XY wanted to go to the Right/Back, not Left/Front. I understand there is an invert homing (but I don't want to change Z axis) Start another thread?
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    No need. OpenBuilds CONTROL > Grbl Settings and use the dropdown to fix your homing. Default is right, back, top (axis maximas)
    If you put your switches there, the default of $23=0 applies. If you moved them elsewhere (for example Left, Front = $23=3) - the dropdown menu allows you to pick which switches are "not where they should be"
     
  10. Holley

    Holley New
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    Got it. However, I am using the Interface controller. And curious, $23=3 is front left, is there a $23=1 and $23=2 for my better understanding of how the machine works
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    You can still set $23=3 from Interface (Tools and Utils > Edit Grbl profile)

    Why =3? Because of the table in Grbl v1.1 Configuration · gnea/grbl Wiki (applies to Grbl v1.1 Configuration · gnea/grbl Wiki too) - inverting X (You want front instead of the default which is back - thus inverse) and Y (you want left, instead of default which is right, and thus inverse) but not inverting Z (Should always home to the top - thats not negotiable - and thus, not inverting)
     

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