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  1. #1
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    Jun 2014
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    1462

    Ballscrew backlash

    I have some backlash in the Y axis, about .0024 approximately, is there an adjustment to the ballnut for this?
    I have adjusted the preload, tightened up the carrier, it wasnt loose but definitely not tight, the backlash is still there.
    I am wondering if there is a rebuild service for these or something short of buying a new one, as its $522.00.

    I noticed this in a probing sequence, in X it is smooth, in Y it makes a slight "bump" when the Y axis reverses which prompted me to look for a problem.

    Any help or information would be greatly appreciated, as I know very little about Ballscrews............

    This is on a PCNC1100 series 3.
    mike sr

  2. #2
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    Ballscrew backlash

    Quote Originally Posted by popspipes View Post
    I noticed this in a probing sequence, in X it is smooth, in Y it makes a slight "bump"
    Hi Mike
    "a slight bump" is a little difficult to diagnose. The Ballnut itself is not really intended to be user serviceable (but some have reportedly done it). The ballnut housing could be loose but that's not likely to cause a bump.
    Is your Y gib perhaps too tight?
    Step
    Edit: a short video might help us.

  3. #3
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    Re: Ballscrew backlash

    Quote Originally Posted by TurboStep View Post
    Hi Mike
    "a slight bump" is a little difficult to diagnose. The Ballnut itself is not really intended to be user serviceable (but some have reportedly done it). The ballnut housing could be loose but that's not likely to cause a bump.
    Is your Y gib perhaps too tight?
    Step
    Edit: a short video might help us.
    Its a bit hard to describe, it shakes the machine slightly when Y reverses direction, I can try to video what is happening, its similar to an abrupt stop and start (accel decel not set correctly) is how I would describe it, on the Y axis only, the X transition is very smooth.
    There are a few very tiny flakes which appear to be metal on the screw itself, it is a bit oily but not profusely so.

    It isnt really noticeable except when probing a pocket, moving the Y manually its very hard to notice unless you know its there and are looking for it. The probing routine changes from Y- to Y+ immediately, that makes it very noticeable.

    cost is a bit of an issue but not near the issue of removing and reinstalling!!
    mike sr

  4. #4
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    Re: Ballscrew backlash

    Saunders just (well, last month or two) posted something on this, I think.

    https://www.youtube.com/watch?v=z6RzDphty_o

    there's some earlier stuff too:

    https://www.youtube.com/watch?v=dDuPcSKb6uk

  5. #5
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    Jun 2006
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    3008

    Re: Ballscrew backlash

    I had some backlash in X a while back that was caused by loose fasteners on the X-axis carrier, so maybe something similar is happening with the Y axis carrier on your. The Y carrier looks a bit harder to get to than the X carrier, unfortunately.

  6. #6
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    Re: Ballscrew backlash

    Quote Originally Posted by MichaelHenry View Post
    I had some backlash in X a while back that was caused by loose fasteners on the X-axis carrier, so maybe something similar is happening with the Y axis carrier on your. The Y carrier looks a bit harder to get to than the X carrier, unfortunately.
    Searching for a loose component would also be my first plan of attack.

    If it turns out that the ballnut is actually worn, then it may be possible to re-pack the ballnut with slightly larger balls. This works best if the screw is worn evenly. It may cause binding near the ends if only the center portion is worn. There may be services that re-build them. Not sure about the cost or how to find them.

    Steve

  7. #7
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    Re: Ballscrew backlash

    Quote Originally Posted by steve323 View Post
    Searching for a loose component would also be my first plan of attack.

    If it turns out that the ballnut is actually worn, then it may be possible to re-pack the ballnut with slightly larger balls. This works best if the screw is worn evenly. It may cause binding near the ends if only the center portion is worn. There may be services that re-build them. Not sure about the cost or how to find them.

    Steve
    Mike, Steve,

    I have checked for loose fasteners etc, now that I think about it, 6 years of making the same small parts with a 3d hole in the center that takes37 to 62 passes roughing, the same for finishing times a thousand or so pieces could be the reason for the bit of backlash possibly??

    I have approx .0024 backlash in the Y, I only notice the abrupt start stop in the pocket probing routine. I need to move some shelving to get at the Y stepper area, so it may take awhile before anything gets done......................

    thanks for all the suggestions!
    mike sr

  8. #8
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    1602

    Re: Ballscrew backlash

    Quote Originally Posted by popspipes View Post
    Mike, Steve,

    I have checked for loose fasteners etc, now that I think about it, 6 years of making the same small parts with a 3d hole in the center that takes37 to 62 passes roughing, the same for finishing times a thousand or so pieces could be the reason for the bit of backlash possibly??

    I have approx .0024 backlash in the Y, I only notice the abrupt start stop in the pocket probing routine. I need to move some shelving to get at the Y stepper area, so it may take awhile before anything gets done......................

    thanks for all the suggestions!
    Is the backlash the same across the travel? If not perhaps you re-fixture the parts so that the critical feature is on a good part of the screw.

    bob

  9. #9
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    Jun 2014
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    Re: Ballscrew backlash

    Quote Originally Posted by rowbare View Post
    Is the backlash the same across the travel? If not perhaps you re-fixture the parts so that the critical feature is on a good part of the screw.

    bob
    I tried this and it doesnt seem to change, I need to take it out and find whats causing the problem, its not that bad but needs fixed but its more of a winter job, too much stuff going on now..........

    I am thinking a 4" knockout cutter thru the bottom of the stand, then make a plug with an oring seal?? I was also thinking 3" risers under the machine and on top of the stand, but I would need to make a platform for the operator to stand on.............

    just cant seem to win for loosing Ha!!

    thanks for the suggestion.
    mike sr

  10. #10
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    Quote Originally Posted by popspipes View Post
    I tried this and it doesnt seem to change, I need to take it out and find whats causing the problem, its not that bad but needs fixed but its more of a winter job, too much stuff going on now..........

    I am thinking a 4" knockout cutter thru the bottom of the stand, then make a plug with an oring seal?? I was also thinking 3" risers under the machine and on top of the stand, but I would need to make a platform for the operator to stand on.............

    just cant seem to win for loosing Ha!!

    thanks for the suggestion.
    Does adding backlash compensation to the INI file help at all? I think ALT + D gets you out of PathPilot and on to the main screen, but I'm not 100% sure.

  11. #11
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    Re: Ballscrew backlash

    Quote Originally Posted by footpetaljones View Post
    Does adding backlash compensation to the INI file help at all? I think ALT + D gets you out of PathPilot and on to the main screen, but I'm not 100% sure.
    I had backlash set for each axis, it left witness marks in the part at 90 degree intervals so I took it out.
    The Y axis had the abrupt stop start in it with or without the backlash setting.
    ctrl+alt+x is how I get to the terminal.

    tnx for the suggestions.
    mike sr

  12. #12
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    Re: Ballscrew backlash

    Quote Originally Posted by popspipes View Post
    I tried this and it doesnt seem to change, I need to take it out and find whats causing the problem, its not that bad but needs fixed but its more of a winter job, too much stuff going on now..........

    I am thinking a 4" knockout cutter thru the bottom of the stand, then make a plug with an oring seal?? I was also thinking 3" risers under the machine and on top of the stand, but I would need to make a platform for the operator to stand on.............

    just cant seem to win for loosing Ha!!

    thanks for the suggestion.
    Interesting idea cutting hole out to get at ball nut. The thought of lifting and supporting the mill whilst ball screw maintenance is carried out fills me with dread. Hopefully I won't have to. Let us know how you get on. I have never tried using such a large hole cutter on steel.

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