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Thread: G0704 - Chasing a more quiet spindle still

  1. #37
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    Default Re: G0704 - Chasing a more quiet spindle still

    I use m4 bolts in mine. I actually use it all the time, like almost daily, for a specific part I maintenance. Yes, I have broken the bolts off many times. Luckily the M4's just break off at the thread, you toss the broken bit out, then move the bolt down.

    I've noticed that having the thread adds a significant amount of holding power as it tends to hold the pin in the pocket. I made a set of pins with smooth shafts and instantly realized they were inferior so I went back to just using plain bolts. The smooth pins want to slip.



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    Default Re: G0704 - Chasing a more quiet spindle still

    Ok so quick update:

    Bearing preload had a lot to do with the noise and 100% of the axial and radial play I had, just as I'd thought. There was a tough spot in the preload nut's threads (or on the spline's threads) that I wasn't able to crack with my homemade spanner wrench. Once I got a real one and something to hold the bottom of the spindle better I was able to tighten it up. I'll have to make sure that the bearings don't get too hot but IIRC I tightened it just enough to remove any play. It's not as smooth as before but that might come as I actually use the bearings.

    At 3500RPM with timing pulleys I'm at ~83-84dB. Better than the 90 something I was originally at but a lot of that noise is still coming just from the pulleys. @maxspongebob I'm going to model up some pulleys then message you to see about turning them for me. My hope is that once the servo motor is working at 5000 RPM (as it should be, apparently I need to exchange my driver for one with a newer firmware) I can get the spindle to be in the ?80dB.



  3. #39
    Member ninefinger's Avatar
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    Default Re: G0704 - Chasing a more quiet spindle still

    Your bearings maybe be bad if you have noise and lack of smoothness. A good bearing should be nearly silent. Got a photo of what setup is making what level of noise?

    Mike



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    Default Re: G0704 - Chasing a more quiet spindle still

    A good portion of the noise at this point comes solely from the motor itself. Running the motor dry with no pulleys it was something like 75dB which is pretty reasonable. I don't know exactly what to expect noise wise from a servo motor other than the DMM servo's website says they are less than 60dB. I assume that means they make less than 60dB as I was measuring an ambient 60ish dB in my garage. Running timing pulleys, which create some noise themselves, I was measuring ~85dB at 3500 RPM. With a good pulley set I think that will be down to 80dB but I won't know until I have them. I'm pretty sure this is the largest source of noise at this point but it seems like even two people with the same setup on different machines can even have a large difference in noise.

    The bearings are new taper roller bearings (that can handle the RPM unlike the stock ones) so they shouldn't be bad. My guess for any lack of smoothness is just the preload nut not being very good. Once I actually had decent preload on them the quieted down a good bit and it pulled out and axial/radial play I could feel in the shaft.



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    Default Re: G0704 - Chasing a more quiet spindle still

    FYI, the 8 hour time weighted average noise exposure limit for general industry is 85dba. So 85dba over 8 hours. But peak can be higher. Keeping it under 100db is a good idea.



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    Default Re: G0704 - Chasing a more quiet spindle still

    Okay, so I measured my machine while making a finishing pass on a bore with a 2 flue 3/8" end mill at 4500 rpm and 27 ipm in 6061 t6. It was 81dba average with my furnace running. Surprisingly low. A roughing cut would be way louder but suffice it to say that 80dba is achievable while cutting.



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    Default Re: G0704 - Chasing a more quiet spindle still

    I have been rebuilding my G0704 spindle with the goal of reducing noise and heat as well. I am very happy with my results and have gone from a ear piercing scream down to a comfortable 75dBA at 1' using an iPhone app. The things that I did that seemed to help the most were:
    -Replacing shot bearings with new AC bearings. Used Kluber IsoFlex NBU15 grease @ 30% fill.
    -Set preload to a correct amount. Original preload was excessive
    -Installed a plastic tube between the spline and the inside bore of the quill tube. This was a light press fit and stops all rattling
    -Changed timing belts from L series to GT3-5mm series with a nylon faced belt. The smaller teeth significantly reduced the running noise.
    -Better machining of new timing belts decreased radial runout from .022" to .001" (The first pulleys were hand shimmed to run "true"
    -Machined a 1 piece spindle motor mount which seals the pulleys in a nearly air tight shell

    The machine is very comfortable to run now, although the bearings still get warmer than desired. I may need to reduce the spindle preload.

    G0704 - Chasing a more quiet spindle still-img_3779-jpg

    G0704 - Chasing a more quiet spindle still-img_3769-jpg

    G0704 - Chasing a more quiet spindle still-img_3776-jpg

    G0704 - Chasing a more quiet spindle still-img_3642-jpg

    G0704 - Chasing a more quiet spindle still-img_3644-jpg



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    Default Re: G0704 - Chasing a more quiet spindle still

    A pair of new pulleys is on the way. Hope these make the mill a bit quieter.

    G0704 - Chasing a more quiet spindle still-2019-02-22-16-59-05-jpg

    Attached Thumbnails Attached Thumbnails G0704 - Chasing a more quiet spindle still-2019-02-22-16-59-05-jpg  


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    Default Re: G0704 - Chasing a more quiet spindle still

    @CL_MotoTech 81dB is beyond reasonable while cutting. I'll be able to see exactly where I'm at once my new pulleys arrive. My guess is it will be about that NOT cutting but we'll see. My servo motor may just make more out the gate noise than typical AC motors (I think that's what you're using, right?).

    @mcardoso Are you using the stock preload nut? I think that's the biggest issue with finding the correct preload. It seems like it's hard to find a middle ground between not having any play in the shaft axially or radially and have it turn smoothly. I may try to make myself a new preload nut and try threadmilling for the first time since the spline is a weird thread IIRC. It also looks like you're using a servo motor. Do you know how loud that gets by itself? E.g. No pulley or belt attached. I noticed something like a 17dB sound difference between ambiance and just that being turned on. It wasn't loud by any means but it seems to be a pretty big jump. I was wondering if maybe AC motors are more quiet than servos but maybe not if you're getting 75dB connected to the spindle. I think I was using XL timing pulleys/belts, whichever Hoss recommended in his plans that you could order direct from SDP/SI. I'm sure those are a large noise maker in the equation.

    Side note, it looks like you have or are gearing up for a power drawbar. Hoping I can join that club myself sometime soon!



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    Default Re: G0704 - Chasing a more quiet spindle still

    Quote Originally Posted by steelcogs View Post
    A good portion of the noise at this point comes solely from the motor itself. Running the motor dry with no pulleys it was something like 75dB which is pretty reasonable. I don't know exactly what to expect noise wise from a servo motor other than the DMM servo's website says they are less than 60dB. I assume that means they make less than 60dB as I was measuring an ambient 60ish dB in my garage. Running timing pulleys, which create some noise themselves, I was measuring ~85dB at 3500 RPM. With a good pulley set I think that will be down to 80dB but I won't know until I have them. I'm pretty sure this is the largest source of noise at this point but it seems like even two people with the same setup on different machines can even have a large difference in noise.
    .
    75dB seems like a lot for just a motor spinning. What does the shaft feel like when you spin it? Can you get a video of it running? Seems to me that the heart of the matter is your servo motor. This is is supported by the fact that its louder with a cast iron pulley - a pulley with no belt shouldn't affect noise at all. Loading up a component that is noisy is just going to make it more noisy, its going to transmit its noise through to the connected components. What type of servo motor is it? BTW - its possible to have bad bearings on new motors - rare but it happens (depends on who made the motor...).
    Do you have the original motor for comparison?



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    Default Re: G0704 - Chasing a more quiet spindle still

    Quote Originally Posted by ninefinger View Post
    75dB seems like a lot for just a motor spinning. What does the shaft feel like when you spin it? Can you get a video of it running? Seems to me that the heart of the matter is your servo motor. This is is supported by the fact that its louder with a cast iron pulley - a pulley with no belt shouldn't affect noise at all. Loading up a component that is noisy is just going to make it more noisy, its going to transmit its noise through to the connected components. What type of servo motor is it? BTW - its possible to have bad bearings on new motors - rare but it happens (depends on who made the motor...).
    Do you have the original motor for comparison?
    It's a DMM servo motor, .75kw. Both the original motor and servo motor feel relatively smooth. The original BLDC feels smoother with less resistance but I would think the servo shaft should naturally have more resistance? Waiting for a new motor driver that's supposed to get here tomorrow then I can get a video of it running. I would double check the noise on the original BLDC but I'd have to rewire it since I had to cut the wires to get it unmounted from the mill. I believe it was pretty quiet though.

    I thought it could also be possible the cast iron pulley wasn't rated for that many RPMs so it could be out of balance and cause noise.



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    Default Re: G0704 - Chasing a more quiet spindle still

    Hi Steelcogs. How are you controlling your DMM servo? I just ordered the same one for my machine, and I'm not 100% clear on how to connect it so Mach3 can control it. Any information or links to other threads would be very much appreciated. Thanks! Mike



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G0704 - Chasing a more quiet spindle still

G0704 - Chasing a more quiet spindle still