VF4 Chatter While Interpolating Holes
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    Default VF4 Chatter While Interpolating Holes

    We have a 2011 VF4 that seems to get a bit of chatter when we interpolate holes. It is always seems to show up at 11 o'clock and 5 o'clock if it was a watch face. Not sure if there are some parameters that will help minimize this? I assume there might be a bit of backlash when changing directions on either X or Y that might cause it? Its not horrible but it is there.

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    Schedule your breaks at those times.

    Boom!



    ....but seriously, what size holes does this become noticeable? Does 'time' change to 1 & 7 when you cut clock-wise?

    TH

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    Nice! I would say over 2". It seems when it is transitioning in X/Y to different direction it shows up. Only in those 2 spots though. I'm not sure on the direction change as we usually climb mill.

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    How many cutting hours are on it? My guess is it may be time for a thrust bearing swap.

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    Quote Originally Posted by Blackhawkxp View Post
    Nice! I would say over 2". It seems when it is transitioning in X/Y to different direction it shows up. Only in those 2 spots though. I'm not sure on the direction change as we usually climb mill.
    Sounds like you have it narrowed down. As to the severity..
    Any measurable egg-shaping when measured at 11 & 5?

    Perhaps go old school and center your X&Y, drop your Z (put a long bar in a tool holder) then put an indicator on everything and see what moves when you manhandle each direction of both the table and the spindle. Thinking you will see either a measurably loose Z while flexing in the Y axis, or in the Y axis itself.

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    cut a 2 inch round boss and measure across the X axis , and directly in the Y axis. and report back. could be backlash. or you could have bad thrust bearing.

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    Sounds like someone needs a ball bar test

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    Quote Originally Posted by plastikdreams View Post
    Sounds like someone needs a ball bar test
    I know people see a ball bar test is the be all do all test. but I have seen them not tell the whole story. I recently was involved in a fadal that was adjusted , and calibrated by a ball bar. after the ball bar the machine would cut a egg shaped part had to cut a part ( the company that did the ball bar and came back, reran and said all is great) and put a actually load on it to find the problem and fix the machine. cut a part and put a load on the axis and spindle. that's truly the tell all and see all.

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    Quote Originally Posted by Hoss710 View Post
    I know people see a ball bar test is the be all do all test. but I have seen them not tell the whole story. I recently was involved in a fadal that was adjusted , and calibrated by a ball bar. after the ball bar the machine would cut a egg shaped part had to cut a part ( the company that did the ball bar and came back, reran and said all is great) and put a actually load on it to find the problem and fix the machine. cut a part and put a load on the axis and spindle. that's truly the tell all and see all.
    I agree, but a ball bar can have useful diagnostic info as well.

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    Quote Originally Posted by Hoss710 View Post
    I know people see a ball bar test is the be all do all test. but I have seen them not tell the whole story. .
    Ball bar test are by nature unloaded so can never tell the whole story or even half of it.
    Servos, bearing and machine slides react differently when under pressure.
    A very handy tool in the box but will not tell you the details when in a cut.
    The old circle diamond square test from the early days of NC tells more but is so much more time consuming to do and analyze.
    At around 10 and 4 o'clock things change a lot on who is the controlling axis as you are into the acc/dec that has to happen and both these ramps have to match.
    A scope on both axis helps but that is also complicated. I'd chase trust bearings first and servo tune second.
    Bob

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    Quote Originally Posted by Blackhawkxp View Post
    We have a 2011 VF4 that seems to get a bit of chatter when we interpolate holes. It is always seems to show up at 11 o'clock and 5 o'clock if it was a watch face. Not sure if there are some parameters that will help minimize this? I assume there might be a bit of backlash when changing directions on either X or Y that might cause it? Its not horrible but it is there.
    .
    servo tuning needs to be done when servo keeps oscillating back and forth often for many seconds before hopefully stopping. many cnc have a servo diagnostic screen to see this. +/-1 might be .00004" and show up as .0001" TIR waves. +/-10 obviously is a much bigger problem. diagnostic screen will show if holding a steady 0 or if oscillating
    .
    when doing any straight or arc moves it can be oscillating back and forth too as it moves


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