Vibrational Dampeners for Mill Bed


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Thread: Vibrational Dampeners for Mill Bed

  1. #1
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    Default Vibrational Dampeners for Mill Bed

    I've machined and installed rotational dampeners for my mini-mill and they work fantastic! Probably one of the best improvements I've made next to cnc retrofit.

    Every now and then, I still have an occasional stall but only if I push the speed of the axis. So I've simply back down the feedrate and we're good to go.

    Now here's the question. Why not put a bar along side the face of the bed itself that has been bored with multiple holes which contain steel balls inside just like the rotational dampeners? I am thinking maybe a 1" wide x .75" tall bar with 0.625" holes and 0.5" balls. Make it 14" long and have 14 holes.

    From what I understand about the dampeners and placing them at the ends of the stepper motors is that they're placed there to handle any vibration that sets up while the table is moving. Well, along those lines, why not try to kill the vibration at the source?

    Does anyone else think this might work as an improvement addition to the others?

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    Attached Thumbnails Attached Thumbnails Vibrational Dampeners for Mill Bed-bar-dampener-mill-bed-jpg  


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    The dampeners are there to dampen torsional vibration induced by the torque pulses produced within the stepper motors themselves. What you suggest would have almost no effect whatsoever.

    Regards,
    Ray L.



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    Thanks for the quick response!

    In my ignorance, I didn't think about that.

    I presumed it was from the harmonics that is developing from the lead screw (due to wobble if not perfectly straight) which translates through the nut which translates down throughout the bed and ultimately at the end of the stepper motor.

    What you're saying makes sense. I suppose the effort making the bar is "not worth the amount of squeeze you'd have to produce to get the juice out of the lemon".

    Oh well, just a thought.....

    Again, thanks for pointing me back to the workshop....LOL!



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    what electronics are you using?
    In the case of say the xylotex drivers, they do not provide any resonance dampening and at certain speeds the motors/axis sounds as if its running thru dirt. Putting a dampener on the axis either on the dual shaft motor or the lead screw or in between the motor and the screw will absorb these "Vibrations" and smooth things out alot!!!!!!
    some have experienced that a simple "FLYWHEEL" weight on the motor works, but if there is something that can rattle it will absorb these frequency

    do a forum search for "my take on stepper dampeners.



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    Yep, using xylotex. As stated earlier, I put dampeners on all the axis and it helped tremendously. Was getting around 10ipm, now I can get around 60ipm, but run at 45ipm just to make sure I don't lose steps to a stall-out.

    Do you concur with HimyKabibble's reasoning? I believe he's correct, but I still have some thoughts as I expressed in my last post.



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    Hi Vogavt

    In deploying stepper motors it is imperative that you do not demand more torque than the motor can supply. Unfortunately the available torque falls with increasing speed / acceleration demanded by the drive to the electronics and motor. Since the stepper provides power as pulses as the coils are switched various electronic tricks are used to try and smooth out the stepping impulse by shaping the applied current / voltage applied at the motor terminals. When correctly applied the resonances can be eliminated or at least very much reduced. Where the rotational resonance cannot be full eliminated the addition of extra inertia in the shape of a fly wheel - directly coupled mass - dampers - will help.

    You are on the right track by reducing the traverse rate and accepting that you would need to upgrade the motors and or power drives to go faster. You also need to have torque in hand to overcome and cutting forces that are "felt" at the lead screw or motor driving the axis.

    Your idea of adding a loose mass to the axis bed would have a marginal and probably detrimental effect as it is coupled to the motors via several loose junctions balls or rollers in the added bit - spring in the lead screw - backlash spring - etc. To be effective dampers are needed close to the source of vibration to be effective and you have done this and seen just what can be achieved.

    Others have posted very well set out information on determining the motor torque required. As it is possible to have too much torque i.e. step to step impulse bigger is not best provided you have sufficient leaving a bit in hand to cope with variations in load due to friction and the cutting forces.

    Hope this helps you relax and enjoy CNC in making some nice parts.

    Regards

    Pat



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    Thanks for all the input Gents! I'll chillax and make some stuff.

    Hopefully others will find this dialog useful in the future!

    Vogavt



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    one of the major draw backs of the xylotex system is that its weak in the knees. 24V........ if your running the 269oz motors cut its power in half or more. they were designed to run with more power. Feeding them 24v where they want 48v or so. its a crippling system to say the least. I have been down that road before. For a small machine it will get you buy, but you will spend more time and money trying to make it work, then you would if you had gotten a g540 and good sized power supply. Im only saying this because like I stated, I have run the xylotex. I made it work, but it took me 2 years or better to find the cause of the issues. Went to the g540, had some hickups, but man let me tell you, its NIGHT AND DAY!!!!!!!!



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    NEMA 23 BIPOLAR STEPPER MOTOR 425 oz-in

    Xylotex 4 Axis Drive and Power Supply
    (1) XS-3525/8S-4 Stepper Motor Driver Board
    (1) 24VDC/5.0A Power Supply with 120VAC Power Cord
    (1) 24VDC Pigtail
    (1) 24VDC Fan

    I also have the cnc4pc C11 board which goes through the xylotex to the steppers.

    If you wish, please look at my wiring diagram and see if something needs to be removed, added, revised, etc.

    Important Legalese: This is what works for my system and I will not be held responsible for any damages if anyone attempts to use it.

    Attached Thumbnails Attached Thumbnails Vibrational Dampeners for Mill Bed-control-box-setup-r5-pdf  


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