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Fusion 360/OpenBuilds Post Process Question

Discussion in 'CNC Mills/Routers' started by Badillion, Dec 4, 2020.

  1. Badillion

    Badillion New
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    This is my first attempt at generating gcode from Fusion 360 and using the OpenBuilds Post Process. I was able to get the file into Fusion 360 but now I dont if I have made a mistake with my settings in the Post Process. I think my problem is with the END OF JOB X POSITION (MM), END OF JOB Y POSITION (MM), and END OF JOB z POSITION (MCS Only) (MM) commands.

    When first tried running the gcode from the home position with the following settings:
    END OF JOB X POSITION (MM) = -10
    END OF JOB Y POSITION (MM) = -10
    END OF JOB z POSITION (MCS Only) (MM) = -10
    The machine would execute the movement and then at the very end trip the limit switches in the negative position past home.

    When I changed the settings to 10 for every command the program would give me an immediate error. Something to do with the way the Z axis started.

    When I tried the following:
    END OF JOB X POSITION (MM) = 10
    END OF JOB Y POSITION (MM) = 10
    END OF JOB z POSITION (MCS Only) (MM) = -10

    I was able to get the outcome in the attached picture. I was able to run three roughening passes without any problems. Everything went like I thought it should until the last movement of the final pass. You can see the final movement cut his fingers off.

    Is there a setting I should change to keep this from happening? Also attached are pictures of my settings and the final gcode output from the processor.
     

    Attached Files:

  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I would start by checking the Grbl settings - making sure Homing Direction is properly configured

    Z homes to the Top. G53 Z-10 should stop just below the switch (without hitting it)

    Also see gnea/grbl
     
    sharmstr likes this.
  3. Badillion

    Badillion New
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    Thank you for the reply.

    I changed the commands all back to -10.

    From what I can tell all the GRBL settings appear correct. The spindle moves in the correct direction when I jog it with the control software. It also homes with the z-axis moving up first and then the x and y axis moving together to the left front corner.

    I ran another program that I created in Fusion 360 and it appeared to run correctly.

    I then immediately set up another piece and re-ran the exact program that had just appeared to run correctly and this time it messed up. The only thing different was a new piece of wood. The very last movement of the spindle was to drag the bit through the piece and then stop at coordinates x=-10, y=-10, and z=-6.48.

    My experience level is such that I don’t know if I have done something wrong in Fusion 360 or if I am doing something wrong in OpenBuilds Control.

    Any idea why it would run correct the first time and then screw up on the second? Do you have another resource that could help me figure out what I am doing wrong?

    Thanks.
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Did you remember to SetZero to tell the Work Coords where the stock is?
     
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    Z home is up, correctly, so that
    END OF JOB z POSITION (MCS Only) (MM) = -10
    is correct, Gcode can move it up to 'home-10mm' for safety moves.
    You can make the -10 less (or is that greater?), if -1mm still clears your limit switch then use that.

    Your XY home is left front, so moving negative from there will obviously hit the limit switches.
    Therefore having
    END OF JOB X POSITION (MM) = 10
    END OF JOB Y POSITION (MM) = 10
    being positive numbers is what you want. Again, if 1mm is enough to avoid hitting the limit switch then use that, else try 2mm and so on till you get a reliable minimum offset.

    You could also turn off the 'going to X,Y at end of job' in the post options, then it will only go to the Z home offset at end, and the work home for X and Y.
     
  6. Badillion

    Badillion New
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    I did because I used the probe to help set it.
     
  7. Badillion

    Badillion New
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    The directions of those positions make sense to me as you explain it. I will try to dial those in. Thank you.
     

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