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PM-727M spindle rattle/vibration

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bbaley

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Hi all,
I have a PM-727M and the spindle (or whatever parts attached to it) rattle like crazy even under the lightest loads.
I can hear and don't think I am imagining "rattle" and vibration even when ZERO load.

I do understand, it is a tiny mill and that the cutter, feed rate, RPM, depth, type of cutter in various materials, et al will contribute to and create "chatter".
But this just seems crazy how much noise it makes even under the slightest load.
My concern is there is something wrong with the unit, or not adjusted properly, or whatever, and I don't want it to waer out, break or etc. pre-maturely (or because of my stupidity which I am flush with)

Not sure if related at all, but the drawbar is way off-center, and I can with two fingers grab the draw-bar/spindle shaft and make it "rattle" easily. that seems like something is loose or not adjusted correctly.

I posted a video here, making a 0.020 cut in aluminum with a 3/8" end mill, very slow feed rate - for reference - it would be great to hear from people and tell me I am crazy, paranoid, overly sensitive or whatever even if there is no issue and theirs does the same.

The vibration/rattle seems to always be present, regardless of steel, aluminum, cutter type, depth of cut, feed rate, etc. just more or less loud and obnoxious.
I would like to add and note that I used an app on my phone to measure the vibration of the head (laying phone on top near drawbar) and also on the table, and it doesn't appear that there are huge jumps in the overall vibration of the "whole" - more vibration/rattle "sound" than anything perceived to be significantly vibrating the material, machine etc.

I will also note, that I do NOT notice any significant "rattle" increase, when drilling (all downward pressure) just the normal sort of
'background rattling'.

And that drawbar off-center thing bugs me. you can see it in the video.

Anyway, thanks for any ideas or thoughts.

 
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WyoGreen

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#2
Looking at the parts list, there should be 2 bearings up there, so the splined shaft should not be rattling like that.

Steve
 

TomS

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#3
The fit between the splined drive sleeve and the splined drive shaft is what keeps the splined shaft centered. If there is excessive spline clearance then you can get the rattling you are experiencing. Interrupted cuts can accentuate the rattle, e.g. fly cutting. I have a PM-932 CNC conversion that has a terrible rattle, particularly at higher speeds: I can go as high as 8800 rpm. It was suggested by another forum member to use high tack grease on the splines to dampen the rattle. It helps somewhat but is not an absolute fix.

Make a bushing that just slips over your draw bar and has a spigot that fits snuggly in the bore of your splined shaft. This will keep the draw bar centered.
 

bbaley

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Make a bushing that just slips over your draw bar and has a spigot that fits snuggly in the bore of your splined shaft. This will keep the draw bar centered.
I am having difficulty envisioning the "spigot" part of your suggestion. do you mean it should be tapered on the OD ?
 

TomS

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Here's the one I made for my Enco mill drill. Does this answer your question.

IMG_0532.JPG
 

bbaley

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Here's the one I made for my Enco mill drill. Does this answer your question.
that helps yes - thank you.
 

Moper361

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I have just the same vibration in my mill,It's annoying
I have done the same as TomS suggested with a high tack grease and yes this does help ,Over the years I've had the mill it has not failed so I think it's just a normal thing for my Chinese mill ,some of my thoughts and ideas that I plan to eliminate or help reduce vibration this would be and I think I will try is

1) on my single phase motor there are only 2 pulses of drive for every shaft revolution as apposition to 3 phase having 4 pole pulses this would be a great advantage and much smoother if I had three phase at my house I'd change to three phase motor however I don't Have this option at the moment .One of my plans is to take of the fan of my single phase motor and there is about an inch and a half of shaft sticking out from end of motor my plan is to machine a small flywheel and fit on here or buy a heavy cast iron pulley To fit on here as a fly wheel then attach some fan blades back onto the underside of pulley or fly wheel for cooling I think the added inersha may help with the vibration and help keep the gears loaded and in mesh more the other option would be to go 3 phase with a for pole motor and a variable belt drive and variable speed drive this would be much superior and much quieter .My electric motor is just about toasted anyway and is getting on in years now so I will try this option first .

These are just thoughts but in my mind I think it would help a little with the problem .
 

bbaley

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added inersha may help with the vibration and help keep the gears loaded.
Thinking about the sound it makes (rattle, clacking, etc) - the gears and mesh/play makes some sense. Precision Matthews did mention there is some play/noise in them to be expected.

Perhaps the bushing consideration by TomS - and additionally seeing if anything can improve the gear mesh....
not looking forward to taking it apart though.
 

Moper361

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Thinking about the sound it makes (rattle, clacking, etc) - the gears and mesh/play makes some sense. Precision Matthews did mention there is some play/noise in them to be expected.

Perhaps the bushing consideration by TomS - and additionally seeing if anything can improve the gear mesh....
not looking forward to taking it apart though.
I would not take apart unless really needed .i would try like Toms has suggested first .
My mill sounds just like yours but it's been running for. Years like that.
I only plan my mods to help improve it.
my mill is getting close to needing some work done on it so when this happens I plan to do a few of my mods to try and eliminate the issue ,I know it's annoying but in reality it has never stopped me using the machine it's just a bit noisy at times that's all
 
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TomS

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#10
I don't believe gear mesh is an issue. I gutted my mill's headstock when I did the VFD upgrade and still have the rattle.
 

bbaley

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in reality it has never stopped me using the machine it's just a bit noisy at times that's all
well that really was my primary concern. hearing that noise just kinda freaks me out, makes you pucker a bit like it's because something wrong and will fail and cost big $$$
 

Moper361

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I don't believe gear mesh is an issue. I gutted my mill's headstock when I did the VFD upgrade and still have the rattle.
Did you go with three phase tom when you switched to VFD ,I'd be interested to know more on this
 

TomS

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Moper361

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Yes, I went with a 2 HP 3 phase motor and a Hitachi VFD. Here's the link to my CNC conversion - https://www.hobby-machinist.com/threads/taking-the-cnc-plunge.24858/page-10. The VFD mod starts with post #283.
Tom when you switched to VFD three phase was your old unit a single phase ? ,I'm just interested to know if going from single phase to three phase and I assume your new three phase motor is four pole ,was there a a difference improvement in smoothness of the running off mill IE less chatter and viabration in spindle as per discussed inner lire posts ? As this was one of my thoughts on trying to improve on mine
 

GunsOfNavarone

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#15
I have the same mill, it has plenty of wear and tear, but no rattle when i grab the draw bar and wiggle it. At some point in the near future, i want to replace the spindle bearings. I would have guessed this is a pretty simple job? With that play/rattle in your spindle, why would you not just not go ahead and replace yours? I think i have a very slow oil leak from gear changing knobs i would need to deal with at the same time. I guess hitting up the PM guys (that I'm told are on here a lot) would be some good advice.
 

Moper361

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Was Just watching you vid again Baily ,this maybe a silly question but in your video when you made the cut did you have the quill lock engaged? As if not this possibly could be some of the noise your experiencing .
 

TomS

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Tom when you switched to VFD three phase was your old unit a single phase ? ,I'm just interested to know if going from single phase to three phase and I assume your new three phase motor is four pole ,was there a a difference improvement in smoothness of the running off mill IE less chatter and viabration in spindle as per discussed inner lire posts ? As this was one of my thoughts on trying to improve on mine
The primary reason for going with the VFD 3 phase conversion was higher rpm which allowed higher feed rates. It's hard to compare the original setup to the new because of the huge difference in rpm ranges. The original motor and headstock gears allowed for speeds up to 1970 rpm, which was smooth, while the VFD 3 phase conversion allows up to 8800 rpm. I can say that at top speed the VFD three phase is very smooth. Keep in mind that at those speeds the stock spindle bearings won't last. You will need to change out the tapered rollers for angular contact bearings.

I'm not sure of the PM-727 top speed but I can say that more rpm is better. You can get the SFM where it needs to be when cutting aluminum for instance which equates to better surface finish.

If you are seriously thinking about going this route I can share some files that mksj gave me for my conversion. He was a huge help to me as well as to others on this forum.
 

robotwizard

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#18
I have just the same vibration in my mill,It's annoying
I have done the same as TomS suggested with a high tack grease and yes this does help ,Over the years I've had the mill it has not failed so I think it's just a normal thing for my Chinese mill ,some of my thoughts and ideas that I plan to eliminate or help reduce vibration this would be and I think I will try is

1) on my single phase motor there are only 2 pulses of drive for every shaft revolution as apposition to 3 phase having 4 pole pulses this would be a great advantage and much smoother if I had three phase at my house I'd change to three phase motor however I don't Have this option at the moment .One of my plans is to take of the fan of my single phase motor and there is about an inch and a half of shaft sticking out from end of motor my plan is to machine a small flywheel and fit on here or buy a heavy cast iron pulley To fit on here as a fly wheel then attach some fan blades back onto the underside of pulley or fly wheel for cooling I think the added inersha may help with the vibration and help keep the gears loaded and in mesh more the other option would be to go 3 phase with a for pole motor and a variable belt drive and variable speed drive this would be much superior and much quieter .My electric motor is just about toasted anyway and is getting on in years now so I will try this option first .

These are just thoughts but in my mind I think it would help a little with the problem .
You don't need to have 3 phase at your house. Just buy a VFD
 

bbaley

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Was Just watching you vid again Baily ,this maybe a silly question but in your video when you made the cut did you have the quill lock engaged? As if not this possibly could be some of the noise your experiencing .
Yes definitely!
It seems to be them same with EVERYTHING locked down tight in all Axes, quill included.
 

bbaley

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I have the same mill, it has plenty of wear and tear, but no rattle when i grab the draw bar and wiggle it. At some point in the near future, i want to replace the spindle bearings. I would have guessed this is a pretty simple job? With that play/rattle in your spindle, why would you not just not go ahead and replace yours? I think i have a very slow oil leak from gear changing knobs i would need to deal with at the same time. I guess hitting up the PM guys (that I'm told are on here a lot) would be some good advice.
I did talk to the PM guys via email, and they mostly said "yes you can expect a little noise/rattle"

Mine seems to be more than just a "little" and not everyone seems to experience the issue so that's why I was researching the issue further.
 
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