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  1. #73
    Member vger's Avatar
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    Default Re: G0704 - Chasing a more quiet spindle still

    Just my 2 cents....
    I worked doing vibration analysis and balancing for many years and found that often times noise came from quite unexpected sources in various machines. One unit I worked on was quite deafening loud when in operation at normal speed, but the noise dropped out as soon as the speed dropped by about 5%. Ended up being a panel on the machine that was resonant at the rotation speed. Stiffening the panel with a bit of steel angle did the trick.

    Locating the source of the noise may require a bit more than just an SPL meter. You might look at an instrument that displays a spectrum of the noise. There are some apps that do FFT even on iPhone or iPad. Once you know the frequency of the loudest (highest peak) then you can start deducing the source. Moving the microphone around near different parts of the machine while observing the spectrum may help.

    Another method of input to the analyzer would be an accelerometer instead of a microphone. The accelerometer can be placed in contact with the machine measuring the vibration at that point. Places like bearing housings, are a good bet to start. If you find there are high frequencies well above the RPM, there are actually databases of bearings that will tell you the frequencies they generate if any damage is present. Terms like “ball/roller pass frequency” etc.

    There are even guidelines to tell you if a bearing is under greased and over greased! Yes, too much grease can cause issues like overheating as well.

    Beyond bearings, things like varying belt tension caused by either worn belts or pulleys can cause vibration and noise. Imagine your belt tension is changing be a few pounds at the speed of rotation! A very slightly bent shaft can be the culprit.

    And then there is mechanical balance. If it’s out of balance and it’s rotating, it’s gonna vibrate.

    Steve

    Trapped on a little island off the coast of Cancun.



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    Default Re: G0704 - Chasing a more quiet spindle still

    My spindle was pretty noisy when I converted to Hoss' L belt drive. The 3D printed bushing he designed reduced the rattle between the spindle and quill drive but it was still pretty loud IMHO. Last year I swapped the L belt pulleys for a set of Multi V pulleys that I turned. I removed the internal quill drive and attached the spindle pulley directly to the spindle. The spindle pulley has a journal that fits into another sealed 6007 bearing that I installed into a spacer at the top of the head. The upper bearing keeps the spindle from flexing under load since the stock upper bearing on the spindle is 5-6" below the top of the head casting. This setup is much quieter than the original L belt setup I used.

    Here's a link to my post with the pulley upgrade if you'd like to look at it.
    https://www.cnczone.com/forums/bench...ml#post2154122



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G0704 - Chasing a more quiet spindle still

G0704 - Chasing a more quiet spindle still