VFD CREATING TRANS NOISE AND VIBRATION?

[fastline12]

We are battling some odd whining noises and vibration in a machine tool. All issues have been isolated to the motor/trans assy which incorporates one motor standing vertically with a heat shrunk gear going into an Al gearbox with straight cut gears to provide 1 speed ranges. There is a total of 3 gears in the trans plus the one mated to the motor.

Vibration can easily be heard and felt and is making it into our part finish. Has been this way for the 3yrs that we have had it but has not seen to got any worse. Vibration amplitude seems to be strongest from the motor but our test devices have been unable to pinpoint the exact frequencies and amplitude but fair to say with our testing that it is in the 40-100hz area. Seems to increase with motor rpm and presents vibration but not as much noise in low range.

Drive is an old Magnatek open loop drive. Drive is likely 15yrs old. Never had a single issue with it though. We do have our monitor go whacky every time the spindle accelerates, which we still cannot pinpoint.

http://www.youtube.com/watch?v=qQ9pWDc3hyY

I did not have an audio recorder on hand so I grabbed the camcorder. Please excuse all the background noise. There is also an audible thump on decel that we just cannot put our finger on. Sounds like a belt thump. Has done it for years.

Any help or ideas would be appreciated. We have been in the trans once looking for this ghost and surprised to find a rather nice looking trans. Gears look great, bearings were in good shape but we could not really test them.

 

[Skogsgurra]

This is a problem that has been known for years. You are lucky if you haven't had in a machine so far.

It is all about the PWM waveform delivered from the drive. Google PWM and drives to learn more.

The standard remedy is to increase the carrier frequency, aka switching frequency. By doing so, you move the vibration up in frequency as well as moving the whining sound into a frequency range that can't be heard.

Look in the inverter's manual how to do it. Or get your supplier on site to do it for you.

What drive is it? I may have the procedure in a manual on my shelf.

Oh, yes. You may have to make sure that the higher carrier requency is allowed. You sometimes need to improve cooling or something.


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[fastline12]

Well, we already have another Mits vector drive for the machine BUT we do not have time to dive into that right now. Right now we need to find the culprit and plan a solution BUT are you saying adjusting the CF could be a fix all or just the whine? Our primary issue right now is vibration. I have been studying the manual to figure out how to get it to coast on Estop without braking so I could see if the vibration goes away.

http://www.yaskawa.com/site/dmdrive.nsf/LEG/MNEN-5JLRL4/$file/TM4231.pdf

here is the manual if you care to help out. I would really appreciate it. Been fighting this for some time now. I am going to be happy and irritated if the drive is causing all of this but my gut says no.... I hope I am wrong.

 

[jraef]

Don't know if it's my connection or not, but that video appears to be blank on my screen, not something I have experienced with YouTube before. Or maybe you just wanted the sound?

If your drive is 15 years old, it may not have the abilitiy Skogsgura mentioned. It may be time to update that system and get a better drive.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[fastline12]

I did not have any video, shudder was shut. Just trying to get an audio clip real quick. Jraef, the carrier frequency is 15khz. If I can somehow prove that the drive is the problem, I already have a nice Mits sensorless unit to put in but need to know where the vibration is coming from.

Can you hear the intermittent chriping? There is also some pretty good vibes you can feel throughout the whole machine. All rotating elements have been disengaged except the trans and motor. Same vibration in high and low range but no chirping.

 

[itsmoked]

Listening to that I would in no way expect that to be drive related. I think you have a problem (in order of likelyhood)

1)gearbox bearing
2)coupling wear/failure
3)bent shaft
4)gear shaft/bearing
5)spindle bearing
6)bent spindle
7)gear tooth
.
.
.
.
.
20)motor balance
.
.
.
.
.
30)drive problem



I would not expect the drive to cause a random-ish chirping noise but rather a much, much, faster vibration.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[fastline12]

You are the winner! Changed program on drive to coast down so i sped it up and let it coast. Vibration is totally mechanical. Chirping is coming from the output shaft in the trans and i suspect balance issues in it as well. Good call.

 

[itsmoked]

Thanks fastline for the come-back. Always nice to get feedback from our discussions.

Keith Cress
kcress -

http://www.flaminsystems.com