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Measuring CNC Router Vibration with Accelerometer — Parallax Forums

Measuring CNC Router Vibration with Accelerometer

ctwardellctwardell Posts: 1,716
edited 2012-06-10 10:01 in General Discussion
I'm going to be setting up a CNC Router as the parts arrive over the next month or so and I'd like to design a system to measure vibration of the spindle.

I'm looking for suggestions on a suitable accelerometer that I can use with the Propeller.

I assume the fundamental frequency of the vibration would be the rotational speed in Hz, so say 400Hz @ 24,000 RPM, but that's just a guess.

I'm also assuming that most of the vibration would be normal to the shaft so maybe a 2-axis accelerometer would be sufficent.

I'll be running the router at speeds from 8000 to 24,000 RPM.

The bit vendor suggested finding the "sweet spot" speeds at vibration minimums and then setting speeds and feed rates based on those values.

Thanks,

C.W.

Comments

  • $WMc%$WMc% Posts: 1,884
    edited 2012-06-07 18:03
    I would use an analog hall-effect sensor placed closed to the spindle.(prox prob)
    '
    A high Vib. means the spindle is deflecting from its concentric normal run-out, And it's reaching a point of failure, or increased wear thats not desired.
    '
    Take a look at GE turbine/Gen sets and Bentley-Nevada controls, For Hi-Vib.
    '
    This is really easy to do if you understand the concept
    '
    I'm on my phone rite now... I don't have the links...When I get home...I'll send you some more info on this.
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2012-06-07 19:38
    I think the vibration may depend on how many flute cutter you use. You can usually hear it when things aren't cutting smoothly. Also, when the natural frequency of the spindle mount matches the flute/rpm , you'll get worse vibration.
  • ctwardellctwardell Posts: 1,716
    edited 2012-06-08 06:59
    Walt,

    Thanks, I didn't realize that proximity sensors were available with resolution that high, that's why I like this forum, there is always something new to learn.

    I think in this case I'm looking more for vibaration of the entire spindle assembly, not the shaft w.r.t. the router housing.

    C.W.
  • ctwardellctwardell Posts: 1,716
    edited 2012-06-08 07:02
    Erik Friesen wrote: »
    I think the vibration may depend on how many flute cutter you use.

    That makes sense, I'll be using 2 or 3 flute cutters, so I guess I should increase my bandwidth to at least 1200Hz.

    Thanks,

    C.W.
  • kwinnkwinn Posts: 8,697
    edited 2012-06-09 00:30
    Will you be using an object like KISS WAV Recorder Driver to record the signal for later analysis or Microphone to VGA to display it in real time?
  • ctwardellctwardell Posts: 1,716
    edited 2012-06-10 10:01
    kwinn wrote: »
    Will you be using an object like KISS WAV Recorder Driver to record the signal for later analysis or Microphone to VGA to display it in real time?

    Initially I just want to stream the data to a PC as serial data so I can display and do analysis on the signal.

    Long term probably just a simple LCD display showing peak and average amplitude for each axis.

    C.W.
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