Vibrations from spindle
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    Default Vibrations from spindle

    I cant get any fine finnish with my ST30ATC and I think its vibrations from my spindle bearings.
    Does anyone think I can reduce these vibrations by using a thicker oil in the spindle?
    (I have some light noises from the spindle or gearbox and I dont want to spend to much money on this old machine even if I think its a great machine)

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    Check belts if your machine has any, and of course the chuck actuator does it run out? Also make sure your jaws are tight.
    It also could be your holder and the turret and the box/linear ways, so many thing.... it is not even funny.

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    What Kaszub said! Belts especially!

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    Quote Originally Posted by Red James View Post
    What Kaszub said! Belts especially!
    Why the belts?
    How can these give vibrations.
    (Its not the same kind of vibrations as a badly placed tool can give, I will try to take a photo)

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    How long was this machine idle?
    Best make a short video with sound when you taking a cut..well make that two cuts one heavy one light.

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    I will take a video.
    I bought it 2-3 years ago and run it since then, the machine was idling for 2 years acording to the seller but I think it might be longer.

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    If the problem is gears perhaps. Check belt. Only temporary. Heavy oil will require a warm up of 30 min.

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    Quote Originally Posted by benganboll View Post
    Why the belts?
    How can these give vibrations.
    (Its not the same kind of vibrations as a badly placed tool can give, I will try to take a photo)
    Belts take a set when they sit idle tensioned around pulleys. Now when the belt is moved around the pulleys there is uneven tension within the belt, a longer/shorter belt length in effect, which results in vibration between the pulleys, which is transfered to the spindle.

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    Its hard to se in the picture but vibratoins comes in a pattern.
    vibrations.jpg

    Here is 2 videos (Machine run at second of three gears)
    ST3 gives vibrations - YouTube
    16 augusti 218 - YouTube

    I have new belts laying in a drawer since I planned to change them years ago
    So I will test see if any difference.

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    When was the last time you leveled the machine, and ensured each mounting pad had roughly equal weight? And is the machine on a rigid concrete pad, or on a suspended floor?

    Another thing that might be of interest is if you can access the belts while the machine is running, and shine a variable frequency strobe lamp on them to see if you can catch the belts "fluttering" during some phase of RPM or load.

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    Its on solid concret, I have moved it and leveled the machine 3 times since I bought it without any difference.
    I will test to:
    1, change belts
    2, change oil in the spindle/gearbox from "Mobil DTE 21" to a SAE 75W-90 gearbox oil. (If not better I will change back to mobile DTE 21)

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    Vibrations can be a result of dead headstock bearings- I have attached simple drawing that shows a pattern on workpiece that can be caused by any of spindle bearings. More viscose oil is not a way in such situation- bearings should be replaced (spindle ones unfortunately are the most expensive ). Also oil play essential role not only as lubricant, but as metallic particle remover from working zone and heat exchanger. It is one of those situations where thicker oil can cause more headaches than we need. Second trouble maker can be spindle motor- and yet another bearing story comes there, but these are less expensive. Belts and vibration? Well these should be very loose to cause such problems and I dont think its whats going on here. Another word here- a lot can say a pattern on already turned part (see attachment)- if the pattern is in the form of waves these can be either worn rails or bearing blocks.
    Attached Thumbnails Attached Thumbnails headstock_vibration.jpg  

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    I looked the videos- so here is some question regarding one called 16 augusti 2018. Is that some plug on chuck hydrocylinder? There is noticeable wobbling of cylinder in video. Maybe some centrifugal forces is causing vibrations.

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    It has wobbling this way as long as I have owned the machine, with or witout anything in it

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    Quote Originally Posted by benganboll View Post
    It has wobbling this way as long as I have owned the machine, with or witout anything in it
    Another silly idea - take a plastic cup partly filled with water (clean coolant mix may be better, no rust risk), place it on headstock or other solid/flat area of lathe, run lathe through rpm slowly enough that you can check for ripple/splash patterns in water surface.

    If consistent RPM where water splash is greatest may be resonant point for out of balance issue or where belt "flap" is greatest. If vibration follows RPM may be clue to balance issue of chuck, or other out of round-out of balance condition.

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    And another - have you checked backlash compensation on Z, and with the machine off, can you place an indicator on the ways and bearing on the carriage, and push it back and forth a noticeable amount? Or rock the carriage, or any other unexpected, uncontrolled movement from it?

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    Default Vibrations from spindle

    As said, could be many things causing your finish problem.

    Your spindle doesn't sound particularly bad for the integral gearbox spindles on these beasts.

    Box way machines like the Slant Turns need ballscrew backlash's checked, and especially the way gibs should be checked/adjusted.

    It's possible you can find a SFM "sweet spot" where the finish is acceptable, experiment on some test pieces to see.

    The draw cylinder runout is adjustable, by altering the torque on the spindle-flange mounting bolts. It needs to runout within .001" max.

    Good luck with it, and keep us posted!

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    Another quick test for the spindle drive not powering the motor with both halves (+ & -) of all 3 phases.

    Run the spindle as slow as you can (1-10 RPM) and watch the motor pulley. Does it turn smoothly, or does it momentarily stop (or slow down) then jump to catch up?
    These problems may be temperature related, works fine when cold and problems after it has been working for awhile.

    If it is not smooth, the power supply in the FR-SE or FR-SF spindle control probably has some missing voltages.
    I have replaced many of these P.S. and cleared up strange problems.

    Bill

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    Quote Originally Posted by cnctoolcat View Post
    The draw cylinder runout is adjustable, by altering the torque on the spindle-flange mounting bolts. It needs to runout within .001" max
    I have seen several that are not even assembled correctly and the spindle actuator just flops around.

    Bill

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    New belts = no difference
    Thick oil = noice from oilpump but not any better.

    (changed back to new DTE21)


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