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Thread: Possible cause for shaft failure?

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    Member Hood's Avatar
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    Default Possible cause for shaft failure?

    Anyone care to speculate on why this motor shaft broke? (see pic below)
    Hood

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    Default Re: Possible cause for shaft failure?

    NOT high cycle fatigue...

    material defect or overtorque. Looks like an acute failure in torsion (clean grain boundaries visible plus lots of smearing on the high spots).

    What is the application/material/treatment?



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    Member Hood's Avatar
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    Default Re: Possible cause for shaft failure?

    It was a servo motor on the Z axis of a Chiron FZ12S VMC I retrofitted.



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    Default Re: Possible cause for shaft failure?

    Quote Originally Posted by Hood View Post
    Anyone care to speculate on why this motor shaft broke? (see pic below)
    Hood
    Misalignment has a habit of doing this over time, this is quite common with hobby built machines also, not so much machining centers but does happen

    Mactec54


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    Default Re: Possible cause for shaft failure?

    The motor was not out of alignment or at least not to any detectable amount. Also the motor connects to the ballscrew via a belt so slight misalignment shouldn't really have been an issue.
    This is an old post and I can't recall how long it ran before the motor shaft snapped but it was before I had actually finished retrofiiting it if I recall. An identical motor was fitted (I fortunately had a spare) and it has been running fine since 2013 without any modifications..



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    Default Re: Possible cause for shaft failure?

    I have just looked at youtube and I posted the video of the first ever job I ran on the Chiron and that video was posted April 2013 so the motor had snapped prior to that so my recollection was correct as the date of my post here is March 2013.



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    Default Re: Possible cause for shaft failure?

    Quote Originally Posted by Hood View Post
    I have just looked at youtube and I posted the video of the first ever job I ran on the Chiron and that video was posted April 2013 so the motor had snapped prior to that so my recollection was correct as the date of my post here is March 2013.
    Yes I can remember your video, I replied because someone else had, and have seen this happen before, seeing it was a belt drive the only why that would happen is if it was over tensioned causing the motor shaft to flex

    Mactec54


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Possible cause for shaft failure?

Possible cause for shaft failure?

Possible cause for shaft failure?