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IndustryArena Forum > OpenSource CNC Design Center > Arduino > strange issue with grbl and arduino
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  1. #1
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    Apr 2021
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    strange issue with grbl and arduino

    hey everyone
    I have this issue that I did my absolute best to fix but with no luck,

    I have a DIY CNC with CNC shield and NEMA 23, the NEMA 23 stepper driver is tb6600

    I control the CNC using inevitables easel.

    here is my issue, whatever grbl settings I use, the cutting will always scale down
    for example, my bed is 450x450mm
    when I want to cut a 10mm x10mm square, it will only cut 2mmx2mm square
    I changed the feed rate and step/mm settings my results changed from 10x10mm square to 14x14mm square, however, if I add too much value the stepper will lose its mind and start spinning in place, I tried making accurate steps/mm and correct feed rate, but still same issue

    note: before I used ramps 1.4 and everything works perfectly, I tried the same settings still no luck
    any possible help?

  2. #2
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    Sep 2010
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    1

    Re: strange issue with grbl and arduino

    Hey.

    So it sounds like the problem is related to the red switch block on the side on the tb6600. They control the microstep modes and have to be in synch with the settings in grbl.
    For example if you have a 200 steps per rotation stepper and a 2mm pitch leadscrew then it would mean that for every 200 steps sent, the screw will turn once. If you have SW1,2,3 turned to "off" then youll be in 32 microsetp mode. This means that every 200 step pulses you send will only cause the stepper to move an equivalent of 6.25 steps (vs full stepp or non-microstep mode).

    Check out those switches first and see what you can see. If you want to keep running at 32nd microstep then youll have to factor the base motor value with the driver microstep value: 200 * 32 = 6400 steps per full rotation

  3. #3
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    Apr 2021
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    4

    Re: strange issue with grbl and arduino

    Quote Originally Posted by AlwynHartman View Post
    Hey.

    So it sounds like the problem is related to the red switch block on the side on the tb6600. They control the microstep modes and have to be in synch with the settings in grbl.
    For example if you have a 200 steps per rotation stepper and a 2mm pitch leadscrew then it would mean that for every 200 steps sent, the screw will turn once. If you have SW1,2,3 turned to "off" then youll be in 32 microsetp mode. This means that every 200 step pulses you send will only cause the stepper to move an equivalent of 6.25 steps (vs full stepp or non-microstep mode).

    Check out those switches first and see what you can see. If you want to keep running at 32nd microstep then youll have to factor the base motor value with the driver microstep value: 200 * 32 = 6400 steps per full rotation
    so I have 8mm lead screw to move my y and x , I have only sw 3 ON , what grbl settings I need to use ?

  4. #4
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    Re: strange issue with grbl and arduino

    Copy and paste here your GRBL settings - $$
    Switches on the drivers determines motor current (1..3) and micro stepping (4..6)
    From micro stepping and screw pitch you can calculate steps/per. If your SW3 is on (1 and 2 off), your driver is set to 16 micro steps, which gives 3200 pulses per one revolution of the motor.
    Assuming that the pitch of your screw is 8mm, your steps/per is 3200 / 8 = 400 steps/mm and that should be your $100, $101 and $102 parameters
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  5. #5
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    Apr 2021
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    Re: strange issue with grbl and arduino

    thank you so much for the time your taking to help me
    here is the current grbl settings :
    $0 = 10 (Step pulse time, microseconds)
    $1 = 25 (Step idle delay, milliseconds)
    $2 = 0 (Step pulse invert, mask)
    $3 = 3 (Step direction invert, mask)
    $4 = 0 (Invert step enable pin, boolean)
    $5 = 0 (Invert limit pins, boolean)
    $6 = 1 (Invert probe pin, boolean)
    $10 = 115 (Status report options, mask)
    $11 = 0.010 (Junction deviation, millimeters)
    $12 = 0.002 (Arc tolerance, millimeters)
    $13 = 0 (Report in inches, boolean)
    $20 = 0 (Soft limits enable, boolean)
    $21 = 0 (Hard limits enable, boolean)
    $22 = 0 (Homing cycle enable, boolean)
    $23 = 0 (Homing direction invert, mask)
    $24 = 25.000 (Homing locate feed rate, mm/min)
    $25 = 500.000 (Homing search seek rate, mm/min)
    $26 = 250 (Homing switch debounce delay, milliseconds)
    $27 = 1.000 (Homing switch pull-off distance, millimeters)
    $30 = 1000 (Maximum spindle speed, RPM)
    $31 = 0 (Minimum spindle speed, RPM)
    $32 = 0 (Laser-mode enable, boolean)
    $100 = 400.000 (X-axis travel resolution, step/mm)
    $101 = 400.000 (Y-axis travel resolution, step/mm)
    $102 = 250.000 (Z-axis travel resolution, step/mm)
    $110 = 1000.000 (X-axis maximum rate, mm/min)
    $111 = 1000.000 (Y-axis maximum rate, mm/min)
    $112 = 500.000 (Z-axis maximum rate, mm/min)
    $120 = 100.000 (X-axis acceleration, mm/sec^2)
    $121 = 100.000 (Y-axis acceleration, mm/sec^2)
    $122 = 10.000 (Z-axis acceleration, mm/sec^2)
    $130 = 420.000 (X-axis maximum travel, millimeters)
    $131 = 420.000 (Y-axis maximum travel, millimeters)
    $132 = 200.000 (Z-axis maximum travel, millimeters)
    ok

  6. #6
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    Apr 2021
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    Re: strange issue with grbl and arduino

    worked flawlessly thank you!!

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