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G4003g Motor Vibration Surface Finish Issues Fixed!!

Discussion in 'GRIZZLY INDUSTRIAL INC.' started by coolidge, Jan 28, 2016.

  1. coolidge

    coolidge United States Active User Active Member

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    Issue: The surface finish when the lathe was new was pretty decent, but quickly deteriorated as the lathe broke in to the point that this is what it looked like after about 15 hours run time. Yikes, this was at 70 rpm about .002 per revolution. It was less severe at 220 rpm but still very poor, mediocre at 320 rpm, not bad at 800 rpm at the finest feed .001 per revolution but even then still had spiraling showing up in the surface finish. Facing also had this spiraling showing up in the surface finish.

    There are numerous reports from G4003G owners regarding this issue, some reporting its an issue with the motor and suggested replacing the motor, others reporting that isolating the motor from the lathe improved or resolved the issue.



    My take on this after methodical step by step testing is, this is the result of a combination of issues.

    1. Poor motor mount design. The factory motor is mounted directly on the lathe bed casting, metal to metal which transmits buzz and hum from the motor directly into the lathe. You can feel this with your hand everywhere on the lathe, headstock, chuck, tailstock. Its accurate to describe it as a buzzing humming type vibration. This is with the belts removed, just the motor spinning in mid air. You can measure this with a .0001 indicator on the chuck and watch the needle buzz back and forth .0001 to .0002 with an occasional spike. So its not the V belts (though using a link belt does reduce V belt vibration).

    2. The factory motor itself did develop a WHA WHA WHA Wooo harmonic which was a contributing factor but primarily it was the buzz/hum into the lathe causing the problem.

    3. Since the lathe initially didn't exhibit this problem my theory is when the headstock was brand new and tight it was able to deal with this motor buzz. But as the headstock broke in and loosened up it became susceptible.

    I decided to replace the factory motor to test some peoples theory that it was just the motor that was the problem. This was not the case.



    As you can see I did make half an attempt to isolate the motor but there was still some metal to metal contact between the motor and the lathe via the edge of the bolt and again you could feel the whole lathe buzzing/humming from headstock to tailstock even with the Baldor Motor. While this did get rid of the WHA WHA WHA Wooo issue on the factory motor, the Baldor spinning true and even, mostly the surface finish issue remained.



    Here's the test I ran after installing the Baldor motor with the above rubber washers. From right to left I turned 3 sections, at 70 rpm, 220 rpm, and 320 rpm. While the surface finish/spiraling issue was reduced, it remained.



    So I ordered some real isolation mounts from McMastercarr. These completely isolate the motor from the lathe, there is no metal to metal contact.



    Here you see them installed. This is not ideal as the motor mounts on the lathe sideways putting a shear force on the isolation mounts. They are rated for 20lbs shear but distort a bit and there is some motor vibration, ideally I would redesign the motor mount so that the motor sits flat down on the isolation mounts like in this photo.



    Drum roll...with these isolation mounts installed the surface finish issues were eliminated! So was the buzz/hum in the lathe. With just the motor running before installing the belts there was zero buzz/hum and just the very slightest occasional something which was the motor wiggling a bit on these rubber isolation mounts, it was like night and day. So I installed the link belt and even with everything spinning, belt, spindle, quick change gears, carriage feeding turning the OD the lathe felt quiet if you place your hand on it, you could feel something with all that stuff rotating but the best way I could describe it is it felt quiet.

    Here's the same test as above, 70 rpm, 220 rpm, 320 rpm, same tool same feed, you can't really tell any difference except for the two lines separating the three turns where I turned off the lathe to change spindle speeds.



    And here's a face cut wow, and this is magnified about 4x, no spiral patterns at all.
     
    Last edited by a moderator: Jan 22, 2017
  2. wrmiller

    wrmiller Chief Tinkerer H-M Supporter-Premium

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    Nicely done! :aok:
     
  3. alloy

    alloy Always looking for the next tool score H-M Supporter-Premium

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    Do you have a part number for those mounts?

    I have a vibration problem on my lathe also and I'm going to have my splash guard off installing my DRO, so perfect time to see if the mounts would help.
     
  4. coolidge

    coolidge United States Active User Active Member

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    Part # 9376K42

    They come in many different sizes and styles on McMasterCarr search "vibration damping sandwich mounts"
     
  5. alloy

    alloy Always looking for the next tool score H-M Supporter-Premium

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    Thanks. That gives me a starting point to find what I'll need.

    Looks like the mounts raised the motor up about 1" from the pics. I'll probably have to buy a new pair of belts, but if it cuts down on vibration it's worth it.
     
  6. tmarks11

    tmarks11 Active User Active Member

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    awesome news. Those are the same sound mounts that I put on my G0709 as well. Just still using the stock motor. It will go one of these days.

    So is this going to change your mind about trading up to a larger lathe?

    I have read a few dozen posts over the years of people gusking about what a big difference it made to swap out the cheap chinese motor for a three phase motor. You are the first one to demonstrate the difference between a quality one phase and a cheap one phase motor. Definitely is a much simpler conversion. Guess I need to go shopping for a new motor...

    Thanks for the before and after product pictures. That shows an amazing difference. You should email those to Grizzly customer service.... not that I would it expect it to make a difference.
     
    Last edited: Jan 28, 2016
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  7. Kernbigo

    Kernbigo United States Active User Active Member

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    i think someone missed the hole story it was not the motor is was the vibration dampening
     
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  8. tmarks11

    tmarks11 Active User Active Member

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    No, I think you didn't read my post:

     
  9. mksj

    mksj Active User H-M Supporter-Premium

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    I had previously read about this by other G4003G owners, they tried all sorts of things. It was one of the reasons I started looking at other lathes after reading some of the G4003G owners frustrations on this issue, and in some case it was never resolved. They sold their problem to someone else. Real makes you wonder about process improvement, or just plain company ignorance. Informative photos real tell the story, job well done.

    Long term using those motor isolation mounts, you may have some issues with sagging or twisting. I assume the motor needs to be mounted in the vertical plane because of clearance issues when using single phase motors.
     
  10. mhagadorn

    mhagadorn United States Steel Registered Member

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    Great work!


    Sent from my iPhone using Tapatalk
     
  11. tmarks11

    tmarks11 Active User Active Member

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    A couple solutions:
    1. Fabricate a motor bracket that puts the motor base plate horizontal (as Coolidge mentioned). This would probably require a good size L-bracket, hard mounted to the lathe, with sandwich mounts under the motor. Challenges here is that the drip tray might interfere on the G4003G (looks like there is enough room on the G0709G), and the L-bracket would have to be thick so it didn't flex.
    2. Fabricate a motor bracket that incorporates sound mounds in both the X & Y plane so you don't have problems with shear forces. I started down this path, buying a couple more sound mounts after I did the initial conversion, but some quick sketching showed this plan would result in a fairly complex bracket arrangement, and the sound mounts have been sitting in my parts bin ever since.

    The sandwich sound isolators are rated to support 20% of their rated load in the shear direction. The downside here is that if you oversize the mounts to accommodate the shear force, you end up with something that isn't as good at sound isolation as if it were mounted in the right direction and the sound mount was sized properly to support the load.

    EDIT: I went back and looked at the mounts I had bought. I just bought the ones that had M10 bolts, which is the same bolt size used in the existing motor bracket. Like Coolidge, this is a 125# mount, rated for 20# in the shear direction. That probably means that it is more than adequate to hold the 50# motor in place for the life of the lathe.
     
    Last edited: Jan 28, 2016
  12. mhagadorn

    mhagadorn United States Steel Registered Member

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    Coolidge, can you elaborate on you test cuts? Depth of cut? Steel grade? Cutting tool? I want to see how mine does. I have always struggled with surface finish.


    Sent from my iPhone using Tapatalk
     
  13. dave2176

    dave2176 United States Active User Active Member

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    Coolidge,
    That's a nice resolution. I think I'll order a set of mounts for mine or is it better to rethink the motor mount first and then isolate it? Would you hang it upside down or stand it on its feet? Maybe upside down at a 45 angle with a hinged mount plate and adjusters front and rear, the kind like some alternators have to tension the belt? You had to change belts (well along with all the other belt changes/types you tried through this journey), what did you end up doing in this case?
    Dave
     
  14. coolidge

    coolidge United States Active User Active Member

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    Ahahahah no! But to be honest I can afford to wait now for the right lathe to come along I'm in no big hurry.

    In fact I did not demonstrate much of a difference between the motors. If anything I dispelled the theory that its the cheaper China motor causing the surface finish issue. The Baldor motor also injected plenty of buzz into the lathe and that's with the thick rubber washers I used to mount it. Now there are reports of G4003G China motors belching smoke and perhaps with further use the buzz would continue to increase I don't know. Remember I only had 15 hours on mine. There was one report of swapping motors for a made in USA Marathon motor made a big improvement. But I wouldn't rush out to buy a new motor unless you were sure the China motor was causing a problem.
     
  15. coolidge

    coolidge United States Active User Active Member

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    I don't think this will hold up long term with the motor mounted sideways putting a shear load on the isolation mounts. I also don't think its ideal in that the motor is more likely to wiggle around mounted sideways. I could be wrong, but I see some distortion already and I'll monitor for a bit.
     
  16. coolidge

    coolidge United States Active User Active Member

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    I likely won't attempt redesigning the motor mount unless the isolation mounts begin to fail but I have sized up the situation. Here are some design considerations...

    1. There is very little room inside the end cover of the lathe for the belt, you would need to maintain the same angle between the motor pulley and drive pulley otherwise you would have to start chopping up the end cover to clear the belt, there's maybe 3/4 inch of clearance around that.

    2. Both the Grizzly and Baldor motors are a tight fit, there's not much room between the chip pan and the cord grips and cords that hang down from the bottom of the electrical panel. If I flipped this Baldor motor upright due to the big capacitor housing on top there's not enough room for it to fit, and certainly not with the added 1 inch of height due to the isolation mounts. BUT...its entirely possible to reposition the electrical cabinet several inches higher to make more room.

    3. Ideally I would not mount the motor to the lathe bed at all, rather I'd bolt the motor mount to the back of the headstock stand, probably isolate the mount from the stand, and the motor from the mount. This would require a longer belt, and possibly a belt tensioner which is not a bad idea anyway. I would certainly design it so its easier to adjust the belt tension, the factory design is a PITA.
     
  17. coolidge

    coolidge United States Active User Active Member

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    These were finish cuts .005 depth of cut on 360 brass using razor sharp polished Korloy inserts CCGT060204-AK. For the record I have tried heavier cuts and more aggressive feeds in testing and the surface finish issues remained.
     
    Last edited: Jan 29, 2016
  18. coolidge

    coolidge United States Active User Active Member

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    Stand it on its feet. The motor should be mounted flat on these isolation mounts compressing them as ideal, or sideways as I did if you must, but not upside down. They are weight rated for compression and shear, but not for pulling apart. 45 degrees on its feet would be fine, basically half way between mounting it upright vs sideways.

    Belt wise I have three sets, the factory belts, made in USA Napa belts with a variable width cog design, and these made in Europe link belts. Using my .0001 indicator the link belts produced the least vibration. The factory and Napa belts were about the same. A serpentine belt would be great, except I read somewhere the drive pulley on the lathe is tapered so that's not an easy bolt on mod.
     
  19. Kernbigo

    Kernbigo United States Active User Active Member

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    i think someone missed the hole story it was not the motor is was the vibration dampening(i stand by my post)
     
  20. tmarks11

    tmarks11 Active User Active Member

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    Fine, now that coolidge clarified that....

    :confused 3:

    My crappy motor + sound mounts surface finish ≠ coolidge's nice motor + sound mounts surface finish, so obviously YMMV.
     
  21. abrace

    abrace United States Active Member Active Member

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    Excellent. As a new G40003G lathe owner (whose lathe is still bolted to the pallet and has never been turned on) I found this interesting.

    My lathe skills are zero, so I assume my surface finish issues will be more of my doing than the lathe when I get started, but this is good data to have in my back pocket. Thanks!
     
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  22. tmarks11

    tmarks11 Active User Active Member

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    I don't know, it looked to me like the motor took you about half way. Regardless, maybe you should strip the motor off before you sell the lathe and keep it for a future modification.
     
  23. coolidge

    coolidge United States Active User Active Member

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    There was significant buzz in the lathe from the Baldor motor even with those thick rubber washers. If I had bolted the Baldor motor on like I had the Grizzly motor bolted on, metal to metal I'm pretty sure the surface finish would have been similar, perhaps a bit smoother eliminating the WHA WHA WHA Whooo of the Grizzly motor. If I have to pull it back off maybe I'll test that and report back. I just don't want people rushing out to buy a new motor thinking that will fix something. Since the isolation mounts are so cheap, less than $3 each I think people should try those first before dropping $324 on a Baldor motor, just my 2 cents worth. The Baldor will be included with the lathe when I sell it, its almost certain I will go 3 phase with a VFD on my next lathe.
     
  24. coolidge

    coolidge United States Active User Active Member

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    You may as well order up the isolation mounts. I had to re-drill and tap the motor mount because the knuckleheads at the factory drilled the holes too far to the left, resulting in the motor being too far to the left, so they just hung the pulley half off the end of the motor shaft to align it with the drive pulley on the lathe (face palm). So if you have to go to all that trouble you may as well install the isolation mounts while you are at it.
     
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  25. tmarks11

    tmarks11 Active User Active Member

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    Cut the knuckleheads some slack. Wasn't their fault that the print said to drill those holes...

    I got to believe that because my G0709 is the same way. Different model lathe, with the same drive pulley only half engaged with the motor shaft.... I am betting that the crude cast iron motor bracket was designed for the original 12x36 lathe, and doesn't really fit the current models but they are using it anyhow....
     
  26. amuller

    amuller United States Active User Active Member

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    Couple of thoughts: All induction motors have discontinuous torque, which tends to make them vibrate about the axis of rotation. The simplest solution may be to use a motor mounted in a cradle with rubber rings. This type of motor is readily available and normally used to drive HVAC blowers. Three phase motors have less vibration for the same reason an engine with more cylinders tends to vibrate less. If a single phase motor does not have a run capacitor, adding one can reduce vibration noticeable by bringing the "start" windings into play as additional "cylinders." Other things being equal, a DC motor running on a well-filtered supply is usually very quiet and vibration-free. But one running on a plain SCR drive without filtration will NOT be either. Likewise, a three phase motor running on a VFD may or may not be quiet and vibration-free. Lots of ways to approach this aside from shock-mounting the motor.
     
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  27. coolidge

    coolidge United States Active User Active Member

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    UPDATE: Okay two issues, first the isolation mounts positions the motor just enough to the rear that the belt rubs on the lathe end cover, it goes on but you can run it that way. As I mentioned in a previous post there's not much room inside the cover. Second issue is with the motor hanging sideways on the isolation mounts the two at the rear are not looking too happy. The pulley helps support the motor at the front but I think the motor is going to have to be repositioned to sit flat.
     
  28. WalterC

    WalterC Active Member Active Member

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    I started to do this a few times, but when I see the huge 3 hp motor sitting in that tight place on the bottom with bolts that are so hard to get to, I decide to get to it tomorrow which is today, but there is always tomorrow.
    There are great isolators used on HVAC compressors with rubber that goes through the bolt area- I might try these as I have a few of them. In fact, I might just do that today.
     
  29. mksj

    mksj Active User H-M Supporter-Premium

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    Mounting the motor in the horizontal plane sounds like a lot of work and trouble for a machine that you are planning on selling. Probably would have been close to the same price to drop a 3 phase motor and something like a Teco 510 VFD drive, and you wouldn't have to deal with the motor capacitors interfering with the mounting. But then, one never foresees all the bumps in the road.

    You may ultimately need to look at other type of mounts, something with a mounting plate with an embedded thread nut for the motor bolt. You also may be better off making a new motor mounting plate out of plate steel or aluminum to mount the motor/feet, and slot the plate for adjustment. Some of the motor manufactures also sell low profile motor adjustable mounting plates. http://www.leeson.com/Literature/pdf/1050/MotorAccessories.pdf

    One of these vendors may be able to direct you to a mounting system for vertical mount shear system,
    http://www.vibrasystems.com/product...ry-mounts/compression-shear-mounts-19/lf.html
    http://us.essentracomponents.com/sh...unt:---1-2-13-threads---hole-diameter-1105130
     
  30. coolidge

    coolidge United States Active User Active Member

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    Converting to 3 phase adding a VFD and controls would have been a LOT more expensive and I'd still have the same issue with the motor having to sit flat on isolation mounts caps or not. This Baldor is no larger than the factory motor in diameter and actually a bit shorter end to end. So while a 3 phase motor would get the caps out of my way and that would be quite helpful, the expense and additional work of a 3 phase VFD conversion cancels that out. Just my 2 cents. IF I was planning to keep the lathe then there's no question I'd do the 3 phase conversion.
     
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