GRBL shield – how to make it running?

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  • June 29, 2012 at 1:33 pm #2385
    Jan
    Member

    I started testing GRBL shield but have problems.
    I played with trimpots and now all 3 green leds shine and motors do not turn properly.
    If I use a command for X axis like g0x1000 , only green led should shine, doesn’t it?
    Similarly for Y axis and Z axis only LED for a particular axis should shine, I think
    Or not?
    Thanks for help

    June 29, 2012 at 2:54 pm #2386
    alden
    Member

    Grbl makes all LEDs turn on at the same time. This is normal. Did you over-torque the potentiometers? They only turn through 270 degrees. If you try to force them they will break and the motors will not turn. If you did this may be why the motors don’t turn.

    -Alden

    June 29, 2012 at 3:46 pm #2387
    Jan
    Member

    Alden,thank you for your reply.
    No, I do not think I over-torqued the potentiometers.
    I tried them again and they still can be turned through 270 degrees only.
    Do you have any other idea what I should check to make GRBL shield run?
    Thanks.

    June 29, 2012 at 4:13 pm #2388
    alden
    Member

    Here are a few things you can try.

    1. Set the trimpots in the middle of the range and leave them there. Almost every motor that grblshield is capable of driving will work in the middle of the range.

    2. Try switching the motors to see if the motor has problems or the channel has problems.

    3. Try running the board with no motors. Do the LED’s light when you issue Gcode commands like G0x10?

    4. Check your grbl settings

    5. Check your motor wiring

    SOme help on these items can be found on the wiki:
    http://www.synthetos.com/wiki/index.php?title=Projects:grblShield

    June 30, 2012 at 4:31 am #2389
    Jan
    Member

    Alden, thanks for your reply.
    I played with tripot of X axis ( but with ONE and only one motor connected) as long as it started properly.I used command like g0x1000.

    Then I did the same ( I set tripot)for Z axis – with one motor connected- but different motor from that I use for X axis.Motor also turned.I used command like g0z1000.

    Then I connected those both X and Z motor to GRBL shield and tried a command like g0x1000.But X motor did not moved properly.It moved only a few degrees and became noisy but did not turn.A similar problem with Z motor.

    Besides I also noticed that $0,$1 and $2 are important for motors to work( turned) properly.
    As I use 0.9 degree motors I think they must have 400 step per revolution.
    My threaded rod is 8mm ( for all axes), microsteps are defaults so $0,$1 and $2 should be
    400*8/1.25=2560

    Is it true that the higher values of $0,$1,$2 the higher current is needed for motors?
    Thank you again for help

    June 30, 2012 at 6:12 am #2390
    alden
    Member

    Sounds like your power supply is not sufficient. What are you using? You should have a supply that provides at least 4 amps (general rule of thumb). Do you have another supply you can try? I’d also recommend 24 volts as opposed to 12v. There is no correlation to $0, $1, $2 that I’m aware of. Also, try a slower move, like g1f300x100y100 and see if that works.

    June 30, 2012 at 10:15 am #2391
    Jan
    Member

    Alden, thank you for the reply.
    So I changed power supply. Now I use 24V/4A but still does not work.
    If there is only ONE motor connected to GRBL shield it works.
    E.g I connect a motor to X and the motor works – I used G1x100 command;
    then I connect another motor to Z axis and issue command G1x100 again. But X motor does not work.
    So I remove Z motor, push reset button on GRBL shield and issue g1x100 command. Now X motor works again.
    But g1f300x100y100 works OK.
    Does it mean I must use even stronger power supply?
    I use steppers 42BYGHM810 that have rate voltage 2.4V and rate current 2.4A.
    Thank you for your help

    July 1, 2012 at 6:15 am #2392
    alden
    Member

    Perhaps it’s your Gcode commands. Issuing G0x100 once will move X to 100. Issue it again and X is already at 100, so it doesn’t move (when in absolute mode, which is the the default). Issue a G0x0 and it will move back from 100 to 0.

    July 2, 2012 at 3:59 pm #2393
    Jan
    Member

    Alden, Thanks for your reply.
    I know if I issue G0x100 for the second time, motor will not turn.Motor stays quiet.
    But I am talking about the fact that I can hear “something” from the motor or the motor turnes only a few angles.
    Here are more details I found out today
    So I bought another power supply – now I use 24V/6.5 but yet GRBL does not work properly.
    E.g.
    I connect a motor to Z axis and enter g1z100( I use G-Code Sender program), sometimes Y and Z axes LED shine but sometimes only Y LED shines and sometimes Z and X axes LEDs where X shines much more stronger .But motor is still connected to only Z axis.

    Another example.
    I enter g1z100( motor is still connected to Z channel). Works OK. Now I push reset button on GRBL shield and enter again g1z100.Now it only moves a few angles.Reset again and enter g1z100 now it works. Again reset, enter g1z100 but it does NOT work.So,sometimes works, sometimes does NOT.
    Are there any test points on GRBL shield I should measure? Is there any testing procedure available?
    Thanks

    July 2, 2012 at 6:08 pm #2394
    alden
    Member

    Is you Z axis actually in the machine or is it just a motor hanging off the Z axis. If it is in a machine I would look at the friction on that axis.

    July 2, 2012 at 6:37 pm #2395
    alden
    Member

    Some further questions:

    1. Did you get or have you performed the Zaxis mod to make the Z axis work at 2x microsteps?
    2. Are you running 200 step or 400 step motors on X, Y and Z? (200 step = 1.8 degrees per step, 400 step = 0.9 degrees per step)
    3. Is your motor part of an assembled Shapeoko or is this behavior occurring when the motor is sitting by itself (unloaded)?

    It looks like whatever the case your grbl settings are off. See DrRob’s calculator at: http://noblesque.org.uk/ShapeOko/grblcalc/
    For 400 step motors, X and Y at 8x microsteps and Z at 2x microsteps the settings should look more like this:
    $0=87.48906386701663
    $1=87.48906386701663
    $2=640
    $3=30
    $4=750
    $5=1100 (and this might even be too high if you Z axis is not very well aligned)
    $6=0.1
    $7=0
    $8=9.8
    $9=0.05

    If you are running 200 step motors change the values and see what you get from the calculator

    July 3, 2012 at 1:43 am #2396
    Jan
    Member

    Alden,thank you for the reply.
    I tested motors separately, not with any CNC machine, so there should not be any friction.
    As I said above I use 42BYGHM810, that are 400 step motors.
    I have not made any mod to your GRBL shield, so there are 8x microsteps.And if motors are tested unloaded, what GRBL setting should I use?
    Thanks for your help

    July 3, 2012 at 5:58 am #2397
    alden
    Member

    Jan, You need to make the Z axis mod to get the axis to 2 microsteps. Here is a link for that. If you do not want to do that yourself we can do this for you if you return your board. But it’s really very easy and takes about 5 minutes with an exacto knife and soldering iron.
    http://www.synthetos.com/wiki/index.php?title=Z_Axis_Mod_for_Shapeoko

    Once you have done this please use these grbl settings for 400 step motors from DrRob’s calculator:

    X/Y belt pitch (inches): 0.08
    X/Y motor (steps/rev): 400
    X/Y pulley teeth: 18
    X/Y microsteps: 8
    Z threaded rod pitch (mm): 1.25
    Z motor (steps/rev): 400
    Z microsteps: 2
    $3 Step pulse width (µs): 30
    $4 Feed rate (mm/min): 750
    $5 Seek rate (mm/min): 1100
    $6 Arc segment (mm): 0.1
    $7 Step port invert mask (binary): 0
    $8 Acceleration (mm/s²): 9.8
    $9 Cornering junction deviation (mm): 0.05

    You should get something like this:

    $0=87.48906386701663
    $1=87.48906386701663
    $2=640
    $3=30
    $4=750
    $5=1100 (and this might even be too high if you Z axis is not very well aligned)
    $6=0.1
    $7=0
    $8=9.8
    $9=0.05

    With your current settings (which you posted on the Shapeoko forum) you may be trying to run grbl faster than its maximum pulse rate.

    July 3, 2012 at 6:20 am #2398
    Jan
    Member

    Alden,
    Thank you for the reply. But as I already said, I am not using it with ShapeOko now and you told me, in another post(http://www.synthetos.com/forums/topic.php?id=615), that I do not need to make that mod if not using with ShapeOko. Does it mean you changed your oppinion?
    Besides that mod is for Z axes only so X and Y should work correctly.Is it so?
    Thanks

    July 3, 2012 at 7:56 am #2399
    alden
    Member

    I stand corrected, you are right. You do not need to make the Z axis mod. I got this confused with another issue.

    That said, perhaps it is good to try to ramp up the motor speed and see if it fails at lower speeds. It could be that the erratic behavior is due to operating on the edge of the maximum speed (seek rate) Try the following sequence of tests:
    G1F50Z10
    G1F100Z20
    G1F200Z30
    G1F400Z40
    G1F500Z50
    G1F600Z60
    G1F700Z70
    G1F800Z80
    G1F900Z90
    G1X1000Z100
    G1X1100Z110
    G0X120

    It is important that the grbl settings do not ask grbl to deliver more than 30,000 steps per second. Can you please post your grbl settings? You might try the tests with the default grbl settings which are something like this (I do not have board here to test from, so I’m going from memory – I may be able to edit later when I get back to my bench) – UPDATE: Edited to agree with grbl defaults

    $0=755.91
    $1=755.91
    $2=755.91
    $3=30
    $4=500
    $5=1000
    $6=0.1
    $7=28
    $8=10 <– This is normally 50, but if you are having problems due to acceleration let’s drop it down to a slower acceleration
    $9=0.05

    Also, can you tell me if you are running a v2 or v3 board? It says so on the silkscreen on the top. This shouldn’t make a difference, but I’d like to know.

    Thanks

    – Alden

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