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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Stepper Motors clunking....loosing steps
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  1. #1
    Join Date
    Apr 2015
    Posts
    2

    Stepper Motors clunking....loosing steps

    Hello All,
    I am looking for an answer for my CNC Router issues. The issue is clunking or loosing steps. I am running four Compumotor S6 Drivers and four S83-135 stepper motors, C10 Bidirectional Breakout board, Mach3 and an old computer. This machine runs beautiful most of the time, I would say 95%. But the motors will start clunking and loosing steps, and sometimes just down right stall.
    What i have tried..

    1. I uncoupled the motors from the shafts and found it still clunks with no load.

    2. Reduced acceleration of the motors and still clunks.
    3. Reduced amps going to motors and still clunks.


    I happened to notice something today with the Pulse Frequency in Mach3, which for the most part is stable at 25000. When the clunking happens the Pulse Frequency drops to 24,996-24,870 the lower the pulse the louder the clunking.


    My question is…..
    1. Would the clunking cause the Pulse Frequency to drop.. OR is the Pulse Frequency drop causing the clunking?

    2. 1. Is the Kernel Speed the same thing as the Pulse Frequency?

    3. 2. If I change the Kernel Speed to 35,000 what changes do I need to do to 'retune' the motors?

    4. 3. Could it just be the old computer?


    Thank to all for any answers.
    John

  2. #2
    Join Date
    Jan 2005
    Posts
    1695

    Re: Stepper Motors clunking....loosing steps

    Look for loose connections.

    Other programs, such as a web browser, could interfere with Mach.

    Reinstalling the OS might help. Sometimes the loaded drivers can interfere with mach.

  3. #3
    Join Date
    Jun 2009
    Posts
    251

    Re: Stepper Motors clunking....loosing steps

    Looks like you have heating issues with the computer. Open the case and have a go with a compressor, also raise the step time and space time on the motor tuning page.
    Tom

  4. #4
    Join Date
    May 2005
    Posts
    1397

    Re: Stepper Motors clunking....loosing steps

    Because the PWM frequency dropped at the same time, It's almost certainly one of these:

    Quote Originally Posted by H500 View Post
    Other programs, such as a web browser, could interfere with Mach.

    Reinstalling the OS might help. Sometimes the loaded drivers can interfere with mach.
    Mach3 has the (rather horrible) problem of running in windows which is NOT a real time OS and can have really long periods of being locked up doing something else. If this just recently started, you might look at restoring a prior state. If it's been ongoing, reinstall... or just get a real motion controller like GRBL or an old DOS computer running TurboCNC. The LinuxCNC guys seem to be happy as well.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  5. #5
    Join Date
    Apr 2015
    Posts
    2

    Re: Stepper Motors clunking....loosing steps

    Hello.
    Is the Kernel Speed the same thing as the Pulse Frequency?
    What would make the Pulse Frequency drop?
    thank you
    john

  6. #6
    Join Date
    May 2005
    Posts
    1397

    Re: Stepper Motors clunking....loosing steps

    As I understand it, Kernel Speed is the rate at which Mach3 tries to recalculate new values. It measures how often Mach 3 tries to run. Between runs, the OS has time to do other things. If the OS is doing something else at the time Mach3 wants to run, then Mach3 may not be able to run at it's desired Kernel Speed.

    Mach3 generates that pulse programmatically, rather than through hardware. If that is true, then anything that puts a load on CPU past a certain point will cause the frequency to drop. In other words, I believe a drop in pulse frequency indicates that the computer is not able to provide Mach3 with the CPU cycles it needs to maintain the desired kernel speed.

    Since Mach3 certainly generates step and direction pulses programmatically, if the Kernel Speed drops, your stepper motors will stutter.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  7. #7
    Join Date
    Sep 2010
    Posts
    717

    Re: Stepper Motors clunking....loosing steps

    Quote Originally Posted by James Newton View Post
    As I understand it, Kernel Speed is the rate at which Mach3 tries to recalculate new values. It measures how often Mach 3 tries to run. Between runs, the OS has time to do other things. If the OS is doing something else at the time Mach3 wants to run, then Mach3 may not be able to run at it's desired Kernel Speed.

    Mach3 generates that pulse programmatically, rather than through hardware. If that is true, then anything that puts a load on CPU past a certain point will cause the frequency to drop. In other words, I believe a drop in pulse frequency indicates that the computer is not able to provide Mach3 with the CPU cycles it needs to maintain the desired kernel speed.

    Since Mach3 certainly generates step and direction pulses programmatically, if the Kernel Speed drops, your stepper motors will stutter.
    That's true. It does stutter with servos too. I overclocked my cpu a bit and could get from 85 to about 95kHz running fine. But at full 100kHz it still stutters.
    (I have also disabled every device and process and service in XP that I don't absolutely need).

    Hub
    Current build: http://www.cnczone.com/forums/diy-cnc-router-table-machines/264838-new-machine-desing-quot-cnm13-quot.html

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