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  • Vibration Damping?

    Okay, I've got this uber-cheap Chinese CNC engraver/mill thing. The spindle is probably running 1000-2000 rpm (since I blew the 24vdc supply and am running a 20vdc laptop supply until my real solution arrives). It's mounted on rubber feet, inside a fiber-board and plex enclosure, sitting on an inch of Styrofoam, and then on 1/4" of rubberish yoga mat (found on the side of the road... I don't do yoga, just wanted to be clear), and then on a wooden cabinet, on a concrete floor. When it's running, I can feel the vibration tickling my feet in the next room, 20 feet away. Said problem might go away when I get more voltage and up the spindle rpm, or it might not. Might get worse.

    It doesn't make much noise, especially with the case lid on. Just purrs along, but it buzzes the floor... in a condo. Not good.

    Putting aside the notion that I'm going to in some way magically fix the rig so that it's in balance and doesn't buzz, any ideas on what I can do to isolate it?

    Right now, it's metal, rubber, foam, rubber, wood, concrete... and it's buzzing the concrete. This thing is tiny... I could put it on a concrete patio block, on the foam, on the rubber, on the... Do you think that would help? Anything else? Layers of wood and rubber? What?

    Mass or squishy, or both? Something else? Anyone ever successfully isolated this kind of vibration?

    David...
    http://fixerdave.blogspot.com/

  • #2
    Density, mass and ductility are what kill vibrations. The heavier it is and the lower the compression rebound ( you want none! ) the better it will damp the vibrations.

    Lead is the absolute winner (short of depleted uranium) for damping. Bolt that thing to a lead slab that weighs 10 times what the machine weighs and ,other than acoustic noise from the device itself, there will be nothing!

    Anyway, it sounds like you are fignting conducted noise, not radiated noise. If there is radiated noise then put the whole thing in a dense box. Dense at the necessary frequencies of course.

    Weird 'science', noise....

    Pete
    1973 SB 10K .
    BenchMaster mill.

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    • #3
      Suspend the entire contraption from the ceiling using latex tubing.

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      • #4
        Originally posted by ikdor View Post
        Suspend the entire contraption from the ceiling using latex tubing.
        I actually do have a roll of tubing, and was actually thinking about that. But, I suspect it would be most annoying to work on while setting up, etc.

        Originally posted by 10KPete View Post
        Density, mass and ductility are what kill vibrations. .. Lead is the absolute winner...
        I don't have much in the way of lead. I could probably cut up some 1/4" plate steel, maybe layered with some more foam or rubber. Lots of scrap MDF kicking around too, but that's starting to get quite a ways from lead. Dense but ductile 'eh?

        I do have a small sheet of lead, probably in the 1/16" range. I suppose I could toss that between some MDF to see if it makes a difference.

        David...
        http://fixerdave.blogspot.com/

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        • #5
          It's pretty hard to beat inertia when dealing with vibration. The mill should be secured to a heavy base, with this base sitting on little piles of cork on top of the cabinet. Find out why it's vibrating so bad and fix that too.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #6
            You could try a paving slab on top of a small tyre inner tube, adjust the pressure in the tube until it floats - this is the quick and dirty isolator some of the scientists use for isolation where I work, usually for small but sensitive lash-ups. It's been the choice of impoverished audiophiles whose turntables are over London Underground tunnels for decades, too!

            Dave H. (the other one)
            Rules are for the obedience of fools, and the guidance of wise men.

            Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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            • #7
              Originally posted by darryl View Post
              It's pretty hard to beat inertia when dealing with vibration. The mill should be secured to a heavy base, with this base sitting on little piles of cork on top of the cabinet. Find out why it's vibrating so bad and fix that too.
              It sits in the box I built for it, probably weighing 4x that of the mill, on rubber feet. The feet just sit in shallow holes I put in the bottom sheet to stop the mill from dancing around. The rubber feet were suppose to damp the vibrations, but obviously don't. Never though to try it without the feet.

              Do you think it would vibrate less if I actually bolted the thing to the box? I hadn't thought of that.

              As for fixing the source... seems to be the spindle motor itself. The vibrations change with the cut, but still there even if it's just spinning in the air, so not chatter etc.. Same vibration with the stupid sleeve collet it came with and an ER11 I put on after. So, probably the motor itself. I think the motors are in the $12 range on Ebay. As I said, it might help spinning faster. I'll find that out later. Honestly, I don't think I'll be forking out $150 for a better spindle motor... not for this thing. Doubt I'll be "fixing" it much at all. Yeah, I put it in a fancy box, but that was mostly to contain the mess as it lives at home rather than the shop. It does work, I used it to engrave some Plex and make an awesome LED nightlight for my kid... photos just don't do it justice. But, a $230 CNC mill is what it it is. I'll not pretend otherwise.

              Originally posted by Hopefuldave View Post
              You could try a paving slab on top of a small tyre inner tube, adjust the pressure in the tube until it floats - this is the quick and dirty isolator some of the scientists use for isolation where I work, usually for small but sensitive lash-ups. It's been the choice of impoverished audiophiles whose turntables are over London Underground tunnels for decades, too!

              Dave H. (the other one)
              You know... my kid's old bike is sitting there on the balcony. I was intending to pull the front brake off and use the mechanism to launch bottle rockets (probably get to that project sometime before he goes to college). That wheel has a tube in it that would be just about the exact right size. If all else fails, I might go that route.

              David...
              Last edited by fixerdave; 03-30-2018, 05:44 AM.
              http://fixerdave.blogspot.com/

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              • #8
                Originally posted by fixerdave View Post
                It sits in the box I built for it, probably weighing 4x that of the mill, on rubber feet. The feet just sit in shallow holes I put in the bottom sheet to stop the mill from dancing around. The rubber feet were suppose to damp the vibrations, but obviously don't. Never though to try it without the feet.

                Do you think it would vibrate less if I actually bolted the thing to the box? I hadn't thought of that.

                As for fixing the source... seems to be the spindle motor itself. The vibrations change with the cut, but still there even if it's just spinning in the air, so not chatter etc.. Same vibration with the stupid sleeve collet it came with and an ER11 I put on after. So, probably the motor itself. I think the motors are in the $12 range on Ebay. As I said, it might help spinning faster. I'll find that out later. Honestly, I don't think I'll be forking out $150 for a better spindle motor... not for this thing. Doubt I'll be "fixing" it much at all. Yeah, I put it in a fancy box, but that was mostly to contain the mess as it lives at home rather than the shop. It does work, I used it to engrave some Plex and make an awesome LED nightlight for my kid... photos just don't do it justice. But, a $230 CNC mill is what it it is. I'll not pretend otherwise.



                You know... my kid's old bike is sitting there on the balcony. I was intending to pull the front brake off and use the mechanism to launch bottle rockets (probably get to that project sometime before he goes to college). That wheel has a tube in it that would be just about the exact right size. If all else fails, I might go that route.

                David...
                Try a piece of thick carpet between the wooden base and the concrete floor.
                'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                • #9
                  It will probably self destruct within a few hours of use, when it does send it back to the main land.
                  Usually motors that run in the matter your describing have a shorter than expected life.

                  JL...........

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                  • #10
                    Vibration through concrete 20 ft away, +A balcony in condo, +A machine tool in condo.

                    That reminds me of staying in hotels where they renovate one half while leaving the other half occupied.
                    The workers go late at night and start early morning and it is amazing how the howl
                    from those hand held air tools carries through the building.
                    Enough to make me grumpy especially if the coffee at breakfast is no good !

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                    • #11
                      Ditch the wood cabinet! You've created a huge bass speaker doing that.

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                      • #12
                        If the motor has a belt drive to the rest of the machine try changing it to a link type belt like a Power Twist. I did that on my older lathe and milling machine. It made quit a difference and stopped the motor vibration from being transmitted right through the machine.
                        Larry - west coast of Canada

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                        • #13
                          Originally posted by Cuttings View Post
                          If the motor has a belt drive to the rest of the machine try changing it to a link type belt like a Power Twist. I did that on my older lathe and milling machine. It made quit a difference and stopped the motor vibration from being transmitted right through the machine.
                          How about sticking it on top of a washing machine
                          Mark

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                          • #14
                            Make a shallow box. In the box put a partly inflated wheelbarrow tire innertube. On the innertube, put a heavy plate. This could be metal, or maybe a scrap piece of granite countertop. Make sure the plate is suspended on the innertube. Put your vibrating thingy on the heavy plate.
                            If the damped mass doesn't stop your vibrations from coupling, probably nothing will.

                            BTW: give some thought to removing the spindle and anything that bolts to it and take them to a pro balancing shop and have the thing dynamically balanced. First have them do the spindle by itself, then with everything added to it, marked so you can remove each piece and put it back just the same way. Should cost about $100, and you will like the results.

                            metalmagpie

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                            • #15
                              All the serious noise and vibration damping setups I've seen have one thing in common. Attach the noise source solidly to something really heavy. Then sit that heavy thing onto something really soft.

                              So the earlier idea of securing (not just resting it) to a heavy base such as a concrete paver slab or hunk of left over granite counter and then floating it on a semi inflated bicycle inner tube is an excellent idea. A tube from a BMX size bike should work just right for a 24x24 size patio paving stone. But you'll want to actually glue or otherwise solidly secure the base to the stone so it can't shake around without also shaking the paver. Just resting it on the paver won't work because it'll dance around.
                              Chilliwack BC, Canada

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