DIY machine travel issues


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  1. #1
    Activation process justicedavid65's Avatar
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    Default DIY machine travel issues

    Hi guys.

    I'm going to try to give as much info as I can about my machine, so bear with me please.

    This is not my first machine, but my first DIY. It is 1500mm x 1500mm with C Beam extrusions, dual C Beams on the X axis. 1610 Ball screws and 15mm Linear rails on all axes.

    I purchased the following package on Ebay for the electronics, link below. I replaced the power supply with 2 48V power supplies.

    https://www.ebay.com/itm/FREE-SHIP-4...UAAOSwbYZXe1GN

    All has been going pretty smoothly with the build and I now have everything together and all of the electronics wired up and the homing switches working.

    The problem I'm having is that the Y and X axis at random times will stop and make a grinding/screeching noises (Z axis works fine). Also, the Y axis has dual motors and one will stop and the other will keep going?

    The grinding/screeching sound like a voltage issue, but I think 2 48V power supplies should be plenty power this machine, and I have adjusted the speeds and acceleration to fix it, but it happens no matter the speed. I am squaring the gantry simply be measuring the right side gantry to the front of the machine and setting the left side to match.

    So I'm really having trouble finding out what is going on.

    Anyone have any ideas about this? Mechanical? Power issue? Electronics issue?

    Thanks for looking and any suggestions you have.

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  2. #2
    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    It sounds like you may have binding in places. The slightest misalignment with your ballscrews and bearings can cause the motors to stall, which is what you are seeing.
    I'd remove the motors, and turn the screws with your fingers to see if there are any tight spots. You need to check the entire length of travels.

    What do you have the current and set to on the drives,and what are your microstep settings?

    Does it stall at really slow speeds? Say, 50ipm?

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Activation process justicedavid65's Avatar
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    Default Re: DIY machine travel issues

    Thanks for the response!

    I have the drives set to full current and 800 microsteps. I don't think I have tried it that slow. I have gone down to around 80ipm.

    So, if I find spots that are binding, how do I fix that? It does seem like it stalls in or around the same place every time.



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    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    If it's binding, you'll need to adjust the machine until it runs smoothly. Make sure the screws aren't bent, and that they are perfectly aligned with the nut, and motors.

    Set the drives to 1600 or 2000 microsteps, and you should get a bit smoother running motors.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  5. #5
    Activation process justicedavid65's Avatar
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    Default Re: DIY machine travel issues

    I will check all of the screws for binding. I am trying to get this machine up to cutting hardwood at 200-250ipm. If I change to 1600 microsteps how much torque will i loose?



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    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    You shouldn't really lose any torque.

    With those motors, you'd be better off with better drives running at 72V. The high inductance (9mH) will be the limiting factor in how fast you can go.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: DIY machine travel issues

    It sounds like an issue I ran into on my first DIY CNC.

    The screws,steppers, and drivers should have have been capable of 200ipm, but if I moved faster then 50ipm it would stall or miss steps.

    The stepper drivers had the on/off dip switches marked backwards. I thought I had set them for 3 amps, but had in fact set them for 1amp.

    Once I reversed the on/off settings on the dip switchs issue was gone.



  8. #8
    Activation process justicedavid65's Avatar
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    Default Re: DIY machine travel issues

    Thanks guys! Great info. Is there a way to check with a multi meter how many Amps my drivers are putting out?



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    Default Re: DIY machine travel issues

    So, I was putting the machine through some test runs last night and noticed something interesting. The place where the motors stall (grinding/screeching noise) are all in the 2 inches from the end.
    Standing at the front of the machine the right Y axis stalls at the back of the machine, the left Y axis stalls at the front of the machine and the X axis stall at the right side. Like I said all of the stalls happen about 2 inches from the end of the ballscrew. Cannot figure out why this is? The machine is square, meaning the distance between extrusions is the same front to back and left to right. The only thing I can think of is that the floor that the stand sits on os not level, but the platform that the machine sits on is a very flat torsion box. Would a non level surface cause these kind of issues?



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    Default Re: DIY machine travel issues

    if it all stalls 2 inches from the ballscrew support, sounds like maybe the ballscrew is not aligned with the ballnut.



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    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    Loosen the ballscrew mounts where it binds, and move the machine all the way to the end. Then tighten them back up. This should align them better.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  12. #12
    Activation process justicedavid65's Avatar
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    Default Re: DIY machine travel issues

    I tried this, twice on each end and it does the same thing. It also seems like it's worse when I first turn the machine on and as I've been using (jogging, I haven't yet cut a single thing on this machine) it for a while it gets better, but still sticks in those spots.



  13. #13
    ericks
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    Default Re: DIY machine travel issues

    Best to remove the motors and turn the ball screws by hand to feel for binding through the whole travel...



  14. #14
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    Default Re: DIY machine travel issues

    Thanks so much for the tips and hope I don't sound too ignorant here, but how will I know what binding feels like when turning the ball screw? Is it any spot that isn't very easy to turn the screw? And, if I find spots that are binding, how do I fix it?

    How would you suggest doing this on a 1500mm machine with 2 Y axis ball screws? Just go back and fourth between the screws and turn a little at a time, or take the gantry off and do each one at a time?

    Thanks



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    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    Is it any spot that isn't very easy to turn the screw?
    Basically, yes.

    And, if I find spots that are binding, how do I fix it?
    Depends on what's causing the binding.


    How would you suggest doing this on a 1500mm machine with 2 Y axis ball screws? Just go back and fourth between the screws and turn a little at a time
    If possible unbolt the nut from one side, then test the entire length.
    Then do the same for the opposite side.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  16. #16
    ericks
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    Default Re: DIY machine travel issues

    Quote Originally Posted by justicedavid65 View Post
    Thanks so much for the tips and hope I don't sound too ignorant here, but how will I know what binding feels like when turning the ball screw? Is it any spot that isn't very easy to turn the screw? And, if I find spots that are binding, how do I fix it?

    How would you suggest doing this on a 1500mm machine with 2 Y axis ball screws? Just go back and fourth between the screws and turn a little at a time, or take the gantry off and do each one at a time?

    Thanks
    It should be smooth....this is the way i checked mine, mine is 1200 mm dual drives.



  17. #17
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    Default Re: DIY machine travel issues

    While searching for a fix today and running the ball screw through I just happened to notice that there was a crack in the coupling between the right Y axis and the motor. After replacing it (luckily had another) this has fixed that problem.

    But, I'm still loosing steps when running gcode? Would this be a problem with the electronics?



  18. #18
    Community Moderator ger21's Avatar
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    Default Re: DIY machine travel issues

    It could be a million different things. But it's most often due to trying to run faster than the motors are capable of.

    It also could be drive settings, wiring issues, noise issues, PC issues, mechanical (binding).

    What acceleration and velocity settings are you using?

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  19. #19
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    Default Re: DIY machine travel issues

    I have x and y set at 3000 and 300 right now. If I didn't specify before, it's only the right side loosing steps I think. I can actually see the right side lagging behind. I have the spindle in the machine, but have not cut anything with it yet.



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