Need Help! Motors turn fine alone, jitter when turned together


Results 1 to 10 of 10

Thread: Motors turn fine alone, jitter when turned together

  1. #1
    Registered
    Join Date
    Sep 2009
    Location
    us
    Posts
    9
    Downloads
    0
    Uploads
    0

    Default Motors turn fine alone, jitter when turned together

    Hello,
    I am using a Chinese CNC kit on a Proxxon Micro-mill.
    https://www.amazon.co.uk/dp/B00IADVM...986871_TE_item

    The only difference is that I did not like their parallel port controller and swtiched to using an Arduino/GRBL to send logic signals to the motor controllers.

    Everything works fine when the axis move alone, but I start running into loud, jittery, rough movements when I try to move multiple axis at a time, even just two.

    The PSU has enough output to handle what I am doing, one of the motors is on half power, the other is full power so I can't imagine this being the problem.

    The weird thing is that even though one axis will move fine, the other will move in the correct amount but very slowly and very jittery, but it will not in fact lose steps, even though it is moving slower than it is set for.

    Grounding is all OK, all I can imagine is something weird is going with the controller being powered by the USB from the laptop, and the motors powered from the PSU?

    Does anyone have an idea?

    Similar Threads:


  2. #2
    Member
    Join Date
    Apr 2009
    Location
    USA
    Posts
    5516
    Downloads
    0
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    Did it work fine with the parallel port BoB?



  3. #3
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    1943
    Downloads
    2
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    I have a couple machines running Grbl and have a few questions:

    1. Are you powering the Arduino only through the USB connection from the computer?
    2. What interface program are you using?
    3. Does it do this when making a single move. or when running a g-code file, or both?
    4. Can you post the Grbl settings from s $$ query?



  4. #4
    Registered
    Join Date
    Sep 2009
    Location
    us
    Posts
    9
    Downloads
    0
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    Quote Originally Posted by 109jb View Post
    I have a couple machines running Grbl and have a few questions:

    1. Are you powering the Arduino only through the USB connection from the computer?
    2. What interface program are you using?
    3. Does it do this when making a single move. or when running a g-code file, or both?
    4. Can you post the Grbl settings from s $$ query?
    1. Yes, Arduino is only powered through USB.
    2. I have tried interfacing through the arudino terminal with the correct settings as well as using the grbl processing GUI, have also tried in linux, mac, other OS, etc.
    3. It does it any time two or more motors move in tandem, even with a simple "G0 X10 Y10"
    4. The GRBL settings are basically standard, I tried tweaking pulse width and post pulse timing to no effect.

    I never got it working via parallel port because I don't have a suitable one.

    Thanks for your help!



  5. #5
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    1943
    Downloads
    2
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    Quote Originally Posted by ink251 View Post
    1. Yes, Arduino is only powered through USB.
    2. I have tried interfacing through the arudino terminal with the correct settings as well as using the grbl processing GUI, have also tried in linux, mac, other OS, etc.
    3. It does it any time two or more motors move in tandem, even with a simple "G0 X10 Y10"
    4. The GRBL settings are basically standard, I tried tweaking pulse width and post pulse timing to no effect.

    I never got it working via parallel port because I don't have a suitable one.

    Thanks for your help!
    What arduino board are you using?
    What version of Grbl?
    Did you get Grbl from the Grbl Github repository or somewhere else?

    Also, post the $$ settings. I need to actually see them.



  6. #6
    Registered
    Join Date
    Sep 2009
    Location
    us
    Posts
    9
    Downloads
    0
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    I am using the Arduino UNO, have tried various arduino boards and various GRBL boards with no luck.

    Here are the GRBL settings:

    Grbl 0.9j ['$' for help]
    $0=5 (step pulse, usec)
    $1=25 (step idle delay, msec)
    $2=0 (step port invert mask:00000000)
    $3=0 (dir port invert mask:00000000)
    $4=0 (step enable invert, bool)
    $5=0 (limit pins invert, bool)
    $6=0 (probe pin invert, bool)
    $10=3 (status report mask:00000011)
    $11=0.010 (junction deviation, mm)
    $12=0.002 (arc tolerance, mm)
    $13=0 (report inches, bool)
    $20=0 (soft limits, bool)
    $21=0 (hard limits, bool)
    $22=0 (homing cycle, bool)
    $23=0 (homing dir invert mask:00000000)
    $24=25.000 (homing feed, mm/min)
    $25=500.000 (homing seek, mm/min)
    $26=250 (homing debounce, msec)
    $27=1.000 (homing pull-off, mm)
    $100=200.000 (x, step/mm)
    $101=9331.200 (y, step/mm)
    $102=200.000 (z, step/mm)
    $110=25.000 (x max rate, mm/min)
    $111=25.000 (y max rate, mm/min)
    $112=10.000 (z max rate, mm/min)
    $120=1.000 (x accel, mm/sec^2)
    $121=0.010 (y accel, mm/sec^2)
    $122=1.000 (z accel, mm/sec^2)
    $130=200.000 (x max travel, mm)
    $131=200.000 (y max travel, mm)
    $132=200.000 (z max travel, mm)
    The reason the Y axis settings look so strange is that the motor is connected to a gearbox to make finer movements.

    Also, today I removed all of the motor controllers and just set it all up through GRBL controller with only the original power supply.
    This seemed to work (both motors moving well together) when there was no load but when I did a small cut I had the same problem I had seen previously.

    I am suspecting this might have something to do with the power supply although it is rated fine...



  7. #7
    Member awerby's Avatar
    Join Date
    Apr 2004
    Posts
    5728
    Downloads
    0
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    How many amps do the motors draw at peak load? How many does your power supply put out?

    [FONT=Verdana]Andrew Werby[/FONT]
    [URL="http://www.computersculpture.com/"]Website[/URL]


  8. #8
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    1943
    Downloads
    2
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    I believe you are using TB 6560 drivers. If so, the step pulse width at 5 us is too short. These drivers need at least 10 us, and depending on the timing capacitor installed on the board could need even longer. Your maximum step rate for your configuration is about 4000 Hz, so not a high stepping rate. at 4000Hz you basically have a step every 250 us, so you can greatly increase the step pulse width without affecting your speed. I would try something like 30us which would be very safe.

    Also, you have your step idle delay at 25 millisec. I personally set this to 255 so that it is on all the time. For your settings I would definitely do that. Take your x and Z axes for example. at 200 step/mm, anything below a 12mm/min feed rate means that your drivers go to sleep between every step. The TB6560 driver have 1/2 current idle which reduces the current when the motor is idle for a certain amount of time, so you don't need Grbl to disable them.

    So, my first recommendations are:

    $0=30
    $1=255



  9. #9
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    1943
    Downloads
    2
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    I also just noticed that your Y-axis accel is set to 0.010 mm/sec^2. At that acceleration rate it will take your y-axis 41 seconds to accelerate from a standstill to your 25mm/min maximum rate.



  10. #10
    Registered
    Join Date
    Sep 2009
    Location
    us
    Posts
    9
    Downloads
    0
    Uploads
    0

    Default Re: Motors turn fine alone, jitter when turned together

    Yeah this is because Y is mapped to a rotary axis, so 1mm=1 revolution, there is also a gearbox, hence why these settings are so strange.
    I changed the power supply today and played with the current settings as well as pulse length, etc. Will give it a run on a real material shortly and report back.



Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Motors turn fine alone, jitter when turned together

Motors turn fine alone, jitter when turned together