Fadal loosing something/somewhere - cumulative error or backlash?


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    Default Fadal loosing something/somewhere - cumulative error or backlash?

    Hey guys, fadal VMC15xt here. Making some casting paterns (long programs, surfacing...) and noticed after a couple of those programs, if I use edge finder and touch reference surfaces in x and y direction - I get about 0,1mm and 0,05mm difference, respectively. Thats about 4 thou and 2 thous,I believe.

    I tried to measure backlash following procedure - I get ZERO backlash reading (current BL values are good, previous owner determined them good).

    I get that difference after running long programs. I used 2 microns (less than tenth) test indicator. Determined the backlash with the small program from the procedure, and via encoder, manually - same reading, both good.

    I have tuned the axis driver quite well not so long ago.
    Is there anything I am missing?
    What could be the cause of my loss of zero point of the piece?

    Thank you all, guys.

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    Default Re: Fadal loosing something/somewhere - cumulative error or backlash?

    Best guess is the screws heat up and change length. Let it all cool down for an hour and recheck.

    Ed.



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    Quote Originally Posted by atex57 View Post
    Best guess is the screws heat up and change length. Let it all cool down for an hour and recheck.

    Ed.
    Seems logical, Ed. Thanks for reply! Haven't considered that. I do not have cooling of the ballscrew, saw it on this forum it exists???? I will think of way to check for it. 4 thous, is that much for it?

    Thank you once again, man.



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    Just a thought - I set the backlash value in thous - vhat if it actually, for example, 1.25 thous? I can't (or can I???) type in that value, if I can measure it? If I really have that situation, it means that, if I have 200 direction changes in one program, i have 200x0.25 thous of error (assuming that I typed in 1 thou as a backlash value).

    I hope you get it.

    Does this means it is error that I have to live with, if I have large programs with many directions changes?



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    Default Re: Fadal loosing something/somewhere - cumulative error or backlash?

    Quote Originally Posted by ginner View Post
    Just a thought - I set the backlash value in thous - vhat if it actually, for example, 1.25 thous? I can't (or can I???) type in that value, if I can measure it? If I really have that situation, it means that, if I have 200 direction changes in one program, i have 200x0.25 thous of error (assuming that I typed in 1 thou as a backlash value).

    I hope you get it.

    Does this means it is error that I have to live with, if I have large programs with many directions changes?
    Backlash does not accumulate. When you go one way you lose the backlash and when you return it returns canceling out.

    Ed.



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    Default Re: Fadal loosing something/somewhere - cumulative error or backlash?

    ...you might be able to use G51.3 to comp for different times of the day of running. Tricky but, possible. Try monitoring your Coolant Temp to use as tool to help.

    DJ



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    Quote Originally Posted by atex57 View Post
    Backlash does not accumulate. When you go one way you lose the backlash and when you return it returns canceling out.

    Ed.
    Thank you very much, Ed. I will have to explain to myself that "backlash does not accumulate" thing, I believe it is so.
    Guess only thing is that thermal expansion then..

    I do not have cooling of the ballnut, your explanations mean a lot to me.

    All the best!



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Fadal loosing something/somewhere - cumulative error or backlash?

Fadal loosing something/somewhere - cumulative error or backlash?

Fadal loosing something/somewhere - cumulative error or backlash?