To rigidify or not to rigidify? - vibration issues
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Think I replied before with an evaluation of what you should do to improve stiffness. I think it still applies. You need to focus on your joints and the thickness of your plates the columns are mounted to. Stiffness is much better to improve over mass to eliminate frequency issues.
Focus on joint preload, moment of area, and do the hand calcs for Beam stiffness yourself. You’ll learn a lot by evaluating it so you can make the correct upgrades.
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@Nxt-1 said in To rigidify or not to rigidify? - vibration issues:
The white inserts for molding the bolt holes were not
I thought we weren't gonna talk about it again:P Anyways I think I would have opted for something hollow to be left in place, maybe - i definitively will now.
Anyawys, thanks for sharing the ups and downs in great length, much appreciated.
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@JoergS5 said in To rigidify or not to rigidify? - vibration issues:
@Nxt-1 thank you for the interesting report. You wrote that you still hear something. Is it still 800 Hz or did the frequency change?
I just did a measurement again at bang on, the same 833Hz, albeit about half as intense. Though I did not control the distance from the frame to the mic, so take the reported intensity for what it's worth.
@TLAS said in To rigidify or not to rigidify? - vibration issues:
Think I replied before with an evaluation of what you should do to improve stiffness. I think it still applies. You need to focus on your joints and the thickness of your plates the columns are mounted to. Stiffness is much better to improve over mass to eliminate frequency issues.
Focus on joint preload, moment of area, and do the hand calcs for Beam stiffness yourself. You’ll learn a lot by evaluating it so you can make the correct upgrades.
I don't seem to be able to find you posting in this thread before. That aside I doubt I can make the printer as silent as I want/need with increasing stiffness. Unless I completely rebuild the machine from scratch and maybe make it out of epoxy granite entirely. But more of a rebuild then what I did in the V2 upgrade (what started this whole thread as well) is really not on the agenda sadly.
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Instead of (or in adittion to) the massive rebar, did you consider using fiberglass, as in chopped strands something like https://www.amazon.com/32-500-4-Inch-Anti-Crak-Concrete-Fibers/dp/B000CODWAE ?
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@bearer said in To rigidify or not to rigidify? - vibration issues:
Instead of (or in adittion to) the massive rebar, did you consider using fiberglass, as in chopped strands something like https://www.amazon.com/32-500-4-Inch-Anti-Crak-Concrete-Fibers/dp/B000CODWAE ?
I did not, GFRC might very well have been a better option compared to the rebar yeah. Especially knowing how the rebar worked out.
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@Nxt-1 said in To rigidify or not to rigidify? - vibration issues:
We have arrived at the moment of truth.
I must nuance the results a bit sadly. While the difference is certainly there and is quite noticeable, it's not perfect and not really acceptable even. I went from being able to hear the printer form all areas of the house to only audible in the next room.
I just did a measurement again at bang on, the same 833Hz, albeit about half as intense. Though I did not control the distance from the frame to the mic, so take the reported intensity for what it's worth.
I think that's a fairly dramatic improvement, although what measure of intensity are you using? Do you mean its down 3dB?... I'm a bit shocked it was as loud as you describe though.
Can you feel much vibration in the aluminium plates across the top? That's what I would try next... -
@theruttmeister said in To rigidify or not to rigidify? - vibration issues:
I think that's a fairly dramatic improvement, although what measure of intensity are you using? Do you mean its down 3dB?... I'm a bit shocked it was as loud as you describe though.
I was quite loud when doing fast all axis moved yes
. Yes I do mean it's down 3dB, actually the 833Hz frequency bin is down 3dB if you look at the frequency spectrum. So it's not entirely fair the say all of it is down 3dB, yet the resonant tone was so dominant that most of the energy in there. Though again I did not perform accurate measurements, with controlled distance and orientation of the mic so don't give to much attention to these values.Can you feel much vibration in the aluminium plates across the top? That's what I would try next...
Yeah, there is some vibration in the plate that hold the bed at the bottom and the one that holds the motors at the top. I am thinking of drilling and tapping some M12 bolt holes so I can attach the top top plate to the plate that hold the motors in the center. This should make it stiffer and is not expensive, nor that much work.
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Interesting experiment; your name and having written some dutch words makes me think you work in Veldhoven ;-). I visit there regularly.
Anyways, just to add some remarks:
- I'm not sure you can "feel" 833Hz with your hands. That's typically lower frequent. I would imagine the concrete drastically changed the vibration part right?
- changing the system "that much" with the frequency remaining about the same is quite strange. It makes me believe it's something else then the frame
- with the probkem being audible, I indeed think that acoustic measures (enclosure('s)) will now help you a lot!
You could also perhaps look at Tune Mass Damper principle. Make one as and test it at different places ;-).
But overall, really nice job man! Cool and it sure was worth reading to the end ;-).
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@QuintBrand said in To rigidify or not to rigidify? - vibration issues:
Interesting experiment; your name and having written some dutch words makes me think you work in Veldhoven ;-). I visit there regularly.
Anyways, just to add some remarks:
- I'm not sure you can "feel" 833Hz with your hands. That's typically lower frequent. I would imagine the concrete drastically changed the vibration part right?
- changing the system "that much" with the frequency remaining about the same is quite strange. It makes me believe it's something else then the frame
- with the probkem being audible, I indeed think that acoustic measures (enclosure('s)) will now help you a lot!
You could also perhaps look at Tune Mass Damper principle. Make one as and test it at different places ;-).
But overall, really nice job man! Cool and it sure was worth reading to the end ;-).
Veldhoven is not to far from me, but I am not from the Nederlands, furthermore, I don't think I have ever been there
On topic, to be honest I have no idea, but I would not be surprised if you were right that 833Hz to to high a frequency to feel. Maybe I felt a lower harmonic of that, not sure. To explain what is happening in reality, there are a number of guesses I can make, but not none can really verify, not does why really matter that much to me anymore
Yeah I really hope the acoustic enclosure I am planning to build will be the final chapter of this story.
I have started a new thread specifically to discuss the enclosure plans here: https://forum.duet3d.com/topic/17725/building-a-sound-dampening-enclosure
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A couple of weeks ago now, I received an installed the proper nema 23 decoupling motor mounts. While the motor is certainly decoupled nicely, the end can jiggle around if you push it. Sadly not really a noticeable noise reduction.
At this point I really think the majority of the vibrations must be coupled via the pulley shaft and bearings, trough the 3D printed mount and into the frame.
I am thinking this will be more or less the end of this thread, as my focus has changed from tackling the source to mitigating the results. You can follow the progress of the enclosure here.
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Going to throw out one more idea - I didn't read all the prior posts as the discussion was all over the place.
If the vertical frame members are resonating, it might be a pretty simple matter to kill the resonance by making them asymmetrical.
What if you were to take three 1 lb (or whatever) pieces of steel and some tee nuts - secure the steel weights to the legs at different heights. That will change the resonant frequencies, and if they are at different heights on each leg, that will kill the symmetry of the vibrations.
Can't promise that it will work out, but it seems like it might be worth trying.
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@dgrat what delta printers kit is that? I’m looking to trash my Rostock because the frame is crappy and that looks to be right up my alley
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@BigMoff96 said in To rigidify or not to rigidify? - vibration issues:
@dgrat what delta printers kit is that? I’m looking to trash my Rostock because the frame is crappy and that looks to be right up my alley
I don't know how else to put it but this beast is unique. The design and fabrication is all done by me (and still progressing).
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@BigMoff96 i feel you bro. Also swtiched from a rostock delta too. If you accept suggestion leave deltas and buy/make something more stable. Delta is very nice to look at, but i switched to a corexy (voron 2) and i would never come back. Now i started printing, with deltas i've only played
just my 2 cents
