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Is it possible for grbl to detect if an axis was moved manually

Discussion in 'Control Software' started by ZCNC, Sep 24, 2021.

  1. ZCNC

    ZCNC New
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    Hello to all,

    I am trying to reduce homing in my program, for example between two executions of a set of gcode.
    Each time it should homing before another job to avoid inaccurate position caused by voluntary or accidental manual movement of an axis.
    But homing is slow and increases the execution time.
    So I thought of skipping a homing if nothing has changed, i.e. if no axis has been moved since the last command of the last gcode set (gcode file).
    Is it possible to know that?
    I use Grbl.
     
  2. Alex Chambers

    Alex Chambers Master
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    If you have $1=255 your stepper motors will be energised when idle, so you shouldn't have to re-home between jobs. Manually moving an axis (knocking it with your arm) shouldn't be possible, and jogging it with your control software will not lose your workplace coordinates.
    What is "forcing" the re-homing? If it's part of your g-code let us know what cad/cam software you are using and which post processor.
    Alex.
     
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  3. ZCNC

    ZCNC New
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    Thanks the $1=255 may be useful on some cases. Actually the operator may wait a long period of time before doing the next job while the CNC is ON. So in that case i can not use it because i do not want the stepper motor to be engaged all the time.
    "the re-homing" is not part of any software, I force the homing by my self in my python script.
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Why not, its highly recommended.
     
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  5. ZCNC

    ZCNC New
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    I was thinking about the longevity of the motor but if it has no impact so why not.
     
    #5 ZCNC, Sep 24, 2021
    Last edited: Sep 24, 2021
    Peter Van Der Walt likes this.
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Absolutely :) thats what they are made for
     
  7. Giarc

    Giarc OpenBuilds Team
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    I speed up homing by jogging the machine to where the homing switches are so it only travels at the homing speed for a few millimeters. It will still be a delay, but much shorter.
     
  8. Alex Chambers

    Alex Chambers Master
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    I sometimes have to tweak a design during a job. My cnc is in my cellar, my design PC is in my attic and I'm old:(. I leave the machine for 1/2 hour or more sometimes - it's not an issue - the stepper motors don't even get hot.
    Alex.
     
  9. ZCNC

    ZCNC New
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    Thanks again Alex, i can say problem solved.
    @Giarc actually i did same like you, now with $1 setup homing delay is not anymore an issue.
     
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  10. David the swarfer

    David the swarfer OpenBuilds Team
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    if the machine is waiting for long periods then do a command like
    G21 G90 G53 G0 X-10 Y-10 Z-10
    before the wait, then the homing only needs to travel 10mm to the switches, then you can retain your power saving setting, or even turn off the stepper power supply between jobs.
     

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