Bent X ball screw?


Results 1 to 11 of 11

Thread: Bent X ball screw?

  1. #1
    Activation process justicedavid65's Avatar
    Join Date
    Sep 2018
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Bent X ball screw?

    I know I'm asking tons of questions lately! thanks everyone for being so helpful.

    I have had my machine up and running for about a month now and I'm still getting random stalls on the X axis and I'm not sure why. I have gone thoroughly gone through all of the electronics and I'm 99% sure it's not that. So, it must be mechanical, right? I was running all kinds of random code today and just looking at the machine as it ran and looking very closely at all of the parts, just to see if I could see something happening when it stalls. I had to run test code for about 15 minutes before I get it to stall. the stalls are very random, but alway seem to happen when I'm cutting something important!

    So, I noticed that the X ball screw Seems to have and up and down motion when it turns? It's slight, but I can see it. I recored a video, but I'm not it can be seen, but I can definitely see it.

    Could this be bent? And if it is, could this be causing my random stalls?

    VIDEO:


    Once again, thanks for all the help!

    Similar Threads:


  2. #2
    Member
    Join Date
    May 2005
    Location
    USA
    Posts
    3819
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    I couldn’t see anything in that video but realize I’m on a cell phone at the moment.

    To answer your question, yes a bent ball screw can cause problems.

    Generally if you are having stalling issues it is a good idea to review the axis mechanically. I’d start with completely disconnecting the ball screw and making sure the saddle moves smoothly from end to end. Since you suspect a bent ball screw I’d take that completely out of the machine to check it against a reference surface. (BE CAREFUL AND AVOID LOOSING YOUR BALLS). If need be straighten your screw. Reinstall the ball screw making sure everything lines up properly. You should be able to drive the saddle from end to end, by manually rotating the screw, without a noticeable change in effort required to turn the screw. Smoothie your desired motion. If it isn’t smooth, especially at the ends of travel your ball screw needs alignment.

    So in a nut shell on a new build verify the mechanics. Do that first but don’t rule out electrical set up. Often people try to set acceleration too high. If you get faults that are totally random across the axis that might point to an electrical setup problem. This especially if the axis a free to move when the machine faults. Some might suggest looking here first but on a new build that hasn’t been carefully check during assembly I’d suggest looking for mechanical issues first.

    By the way there are always other possibilities. For example you could have a bad ball in the ball nut that only catches once and a while. Problems like these can be tricky because the “catch” can sometimes go away when the steppers / servos fault. Conversely you could have a bad spot on the screw itself but that would be less random. Even your leadscrew thrust bearings can develop similar issues. The struggle between “is it mechanical or electrical” can be very frustrating at times.



  3. #3
    Member
    Join Date
    Mar 2010
    Location
    United States
    Posts
    558
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    Just an opinion but I would be looking at the electronics or software setup unless there is some obvious binding somewhere in the axis.

    I know that's not much help... have you tried swapping parts from one axis to another (motors, cables, drivers, etc.)? If you're lucky the stall will follow the part that you swap...

    Adam,

    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


  4. #4
    Member
    Join Date
    Jan 2005
    Location
    USA
    Posts
    10006
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    Quote Originally Posted by justicedavid65 View Post
    I know I'm asking tons of questions lately! thanks everyone for being so helpful.

    I have had my machine up and running for about a month now and I'm still getting random stalls on the X axis and I'm not sure why. I have gone thoroughly gone through all of the electronics and I'm 99% sure it's not that. So, it must be mechanical, right? I was running all kinds of random code today and just looking at the machine as it ran and looking very closely at all of the parts, just to see if I could see something happening when it stalls. I had to run test code for about 15 minutes before I get it to stall. the stalls are very random, but alway seem to happen when I'm cutting something important!

    So, I noticed that the X ball screw Seems to have and up and down motion when it turns? It's slight, but I can see it. I recored a video, but I'm not it can be seen, but I can definitely see it.

    Could this be bent? And if it is, could this be causing my random stalls?


    Once again, thanks for all the help!
    Looking at the Ballscrew it is not bad enough to cause your stalling unless you are getting raking from one side to the other with the Gantry

    Your electrical strip connector, what is that all about, sure is not how your machine should be wired, need more photos of you wiring I would say this is where your problems are

    Mactec54


  5. #5
    Activation process justicedavid65's Avatar
    Join Date
    Sep 2018
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    Thanks for the advice guys, as far as electrical, I have rewired everything. The X is wired exactly like everything else, and I have tried switch motors from the Y axis and it doesn't solve the problem. I really think it's mechanical. I measured it with a dial indicator today and the distortion on the rotation is about .006". Not sure if this enough to cause the stalls or not though?



  6. #6
    Member
    Join Date
    Jun 2010
    Location
    Australia
    Posts
    3765
    Downloads
    4
    Uploads
    0

    Default Re: Bent X ball screw?

    That is quite a long thin ball screw. If the axis is moving fast, you may be getting some whip in the shaft - ie it could be vibrating.
    The serious cure for this is a ball screw with a bigger diameter (ie stiffer) - which can be $$.
    A simple test you can run is to drop the speed to half or maybe one quarter and see if the problem persists. If it does not persist, then you have whip.

    Cheers
    Roger



  7. #7
    Member Sterob's Avatar
    Join Date
    Jan 2007
    Location
    Australia
    Posts
    367
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    I had to remove my steppers and wind all the axis's by hand to find all my issures.( I found lots. )
    If you can feel any binding in EITHER direction, then you have a mechanical issue.



  8. #8
    Activation process justicedavid65's Avatar
    Join Date
    Sep 2018
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    It's not speed, It happens at very slow speeds and my other axes are fine and I've had them running at 400ipm with no issues. I plan on taking the motor and the ball screw off today and checking for bends. I took another video last night and you can clearly see the screw move up and down on it's rotation. Link below.





  9. #9
    Activation process justicedavid65's Avatar
    Join Date
    Sep 2018
    Posts
    43
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    Mystery solved! I removed the ball screw and nut and ran the nut up and down the screw and it didn't flow very well and then it just stuck where I couldn't move it at all. I suspect the balls were binding up inside, which is why it was so random. I removed the nut and repacked the balls...what aPITA!!! It took me 4 tries to get it correct, but finally did. when finished I could just hold screw perpendicular to the floor, hold the nut and it would lower all the way along the screw just by the weight of the screw.

    Installed it on the machine and everything is great. Sounds better and I have been running it non stop for about an hour with no stalls. I think it's fixed.

    Thanks to everyone who offered advice!!!



  10. #10
    Member
    Join Date
    Jun 2010
    Location
    Australia
    Posts
    3765
    Downloads
    4
    Uploads
    0

    Default Re: Bent X ball screw?

    Fair enough. I have done that too: strip a ball nut down, clean out the gunge, and rebuild it. Very educational exercise. Best done over a large tub or basin, so no balls get lost!

    Cheers
    Roger



  11. #11
    Member
    Join Date
    May 2005
    Location
    USA
    Posts
    3819
    Downloads
    0
    Uploads
    0

    Default Re: Bent X ball screw?

    This is good news! Sometimes it is hard to find these random catches or jams. If the ball nut and screw are new and you didn’t find any significant contamination you may have a problem with one or more balls. So keep this in mind if the problem returns.

    Best of luck!


    Quote Originally Posted by justicedavid65 View Post
    Mystery solved! I removed the ball screw and nut and ran the nut up and down the screw and it didn't flow very well and then it just stuck where I couldn't move it at all. I suspect the balls were binding up inside, which is why it was so random. I removed the nut and repacked the balls...what aPITA!!! It took me 4 tries to get it correct, but finally did. when finished I could just hold screw perpendicular to the floor, hold the nut and it would lower all the way along the screw just by the weight of the screw.

    Installed it on the machine and everything is great. Sounds better and I have been running it non stop for about an hour with no stalls. I think it's fixed.

    Thanks to everyone who offered advice!!!




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

Bent X ball screw?

Bent X ball screw?