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Machine wont run after failed calibration

Discussion in 'CNC Mills/Routers' started by trevor sachs, Aug 3, 2022.

  1. trevor sachs

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    Started off with g-codes from Easel not cutting correctly, all the cuts would stack on top of each other. For example, cutting a pumpkin the eyes would be where the mouth should have been. That lead me down the road of trying to recalibrate my machine. During a x axis calibration I accidentally entered values and now my X axis is constantly 84546.600. After that my machine is basically unresponsive. I cannot move anything and when I do I get "machine needs to idle before jogging", resetting it doesn't do anything, I tried uninstalling and reinstalling the software again. Same issue. Any help would be appreciated
     

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  2. Peter Van Der Walt

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

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    Grbl settings is not stored in the software - it's stored onboard in your controller's EEPROM

    Use the Grbl Settings tab to restore your last Grbl settings backup, or load a profile / configure custom settings as needed

    Unable to review your screenshot, resolution is too low its unreadable: See Open Snipping Tool and take a screenshot to take a proper screenshot if you need us to check it out
     
  3. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

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    While it is possible to calibrate an entirely unknown system (1), the process is simplified by making a few assumptions to get a starting point.
    Most stepper motors are 200 steps / rev
    Blackbox defaults to 8x microstepping.
    This gives us 200*8 = 1600 steps per rev.
    If we set steps/mm to 1 and command a move of 1600mm we should see the motor do 1 revolution. If it does not we
    have made a wrong guess at the steps/rev or the microsteps. In the end , GRBL does not care, it uses the steps/mm value to calculate how many steps to move and has/needs no idea of the actual mechanics.

    Next is the leadscrew pitch, or belt pitch? Lets assume a leadscrew of 8mm pitch, so our 1600 steps will move the gantry 8mm.
    1600/8 = 200 steps per mm would be good starting point.
    If we set this and tell it to move 1mm we can easily tell if we are close or not.
    Moving 8mm should make the motor turn once, and so on.
    (for belts, use the calculator at GRBL settings calculator to find an initial value)

    We can now use the serial console to set this value as a starting point.
    The variables are $100 $101 $102 for XYZ steps/mm respectively.

    Type in the new value like this
    $100=200
    and press enter and you should see the reply
    Code:
    [09:04:08] [ $100=200 ] ok
    
    but wait, OpenbuildsCONTROL makes it even easier if we use the GRBL Settings tab, just scroll down to the $100 edit box, enter 200, and then click the blue save icon at top left.

    This value of 200 represents the ideal leadscrew pitch, since they are made by rolling (unless you pay a kings ransom for ground leadscrews) the pitch is always a little long, so after setting the starting point we must do a few calibrations, resetting the BB between attempts.

    Note (1)
    I have actually done this to prove it to myself, I should make a video of it (-:
    I set the steps/mm to 1 and then messed around with jogging to get the mechanism to move about 50mm, then used the numbers I had at that point to do the calibration. The first new steps/mm was still a bit off so I repeated the calibration. I found that after 3 calibrations you don't get any better, it starts to oscillate around (slightly short/slightly long) - I suspect that using more accurate means of measuring the motion than a plastic ruler will reduce this (-:

    if you have never seen threads being rolled.....
     
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  4. JustinTime

    JustinTime Veteran
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    Holly Cow! 340k pound of force! 75HP!
    Thanks for posting it, David.
     
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  5. Alex Chambers

    Alex Chambers Master
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    Wow! And I always thought they were rolled into a hot bar.
    Alex.
     
  6. trevor sachs

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    Thanks for the great information. I got the machine running again, tried it this morning and everything seemed to sort itself out. Now as to the steps. The axis are all 8mm lead screw running openbuilds high torque motors. with 200 steps set the x and z axis work as should, i ask for 3" and the machine physically moves 3". With my dual Y axis I have to have the steps set to 800 in order for it to move correctly. with the y axis set at 200 steps, the machine will display that it moved 3" and only move roughly 3/4". i dont mind running it at 800 steps, just confused as to why its not the same.
     
  7. Alex Chambers

    Alex Chambers Master
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    @trevor sachs what controller set up do you have? If its a grbl controller can you post your grbl settings?
    Alex.
     
  8. trevor sachs

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    After further investigation I believe the machine is sorted out. I contacted Easel customer support and he recommended doing $RST=* command which re entered the motor steps and after that it worked fine. I also think that the machine has to be connected to Easel while making the g-code or it doesn't apply the machine settings. I could be wrong but that's what it seems like to me. I also dropped some pics of my settings incase anybody sees something that can be improved. super green to this so always open to recommendations. thanks in advanced.
     

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