***Resolved*** NEW PM-1440HVT-2 Lathe (PM fixed it)

[Dabbler]

@paynerd I listened to this thread at the beginning, and decided to wait and see what PM came up with before offering advice. I'm really glad they got to the heart of the matter on the first try, even if that try was bumpy. I had confidence that PM would get you there, one way or the other.

You seem to have a sweet machine! I hope this episode hasn't soured you on using this machine now.

Too bad no one took me up on my $20 bet.

I was tempted. (but to take the bet I felt was unfriendly).

I had my own theories also, but I thought it was about 50% chance it was the VFD. My own experience would have pointed to an incorrect current setting for the motor, which I would guess was step 25. The other 50% I felt was a bellmouth bushing on the large gear (BTW)...

Ah heartfelt congratulations on your new purchase and your resolution of the problem!

 

[Sticks]

You put oil back in the gearbox didn't you?

Easy to miss a little but very critical step like that while trying to sort problem out.

Glad to hear you are finally up and running.

 

[Beckerkumm]

What is the purpose of the axial play in the gear? I've not seen that, especially the way it springs back. Dave

 

[Ischgl99]

Well I get to eat some crow, but glad it worked out. I have had problems with motors cogging before auto-tuning, but haven't come across anything like what you experienced. I would be curious to know what the parameters were before you changed them. I have worked on some of the 1440EV lathes from Eisen that used the Yaskawa VFD's which I am quite familiar with and used on many VFD installs. I haven;t used any of the Toshiba or Delta drives, every VFD/motor combination can be different, but kudo's to PM/QMT working it out with you, they did a very good job.

I got side tracked by how loose that gear is, I never expected that much play would be normal. I should have suspected a natural frequency problem by how quickly it developed at a certain speed.

I spent a portion of my career heavily involved with vibration analysis, VFDs cause more vibration problems in motors than most people realize. A lot of problems like this are hidden most of the time because they are not bad enough, or outside of the operating frequency enough that it doesn’t excite a natural frequency. I think he got unlucky that the induced vibration from the poorly tuned parameters coincided with the belt natural frequency, another machine with the same parameters might not cause the same problem, but the potential is still there.

 

[tim81]

I got side tracked by how loose that gear is, I never expected that much play would be normal. I should have suspected a natural frequency problem by how quickly it developed at a certain speed.

I spent a portion of my career heavily involved with vibration analysis, VFDs cause more vibration problems in motors than most people realize. A lot of problems like this are hidden most of the time because they are not bad enough, or outside of the operating frequency enough that it doesn’t excite a natural frequency. I think he got unlucky that the induced vibration from the poorly tuned parameters coincided with the belt natural frequency, another machine with the same parameters might not cause the same problem, but the potential is still there.

Or if the resonant frequency changes due to variance in load. He was not having issue at speeds in idle. So I wonder how will it do on variating loads. But I guess it should be fine.

Tim

 

[npalen]

I was going to suggest, at a point in the thread, a piece of clear plexiglass to replace the top cover to allow a visual while the lathe was running.

This thread has been of great interest to me as I have some noise issues since replacing the motor with a VFD driven one on my Grizzly G0602 lathe. I've suspected the VFD from the git go but still haven't figured out if its that or the spindle bearings. May have to take another look at parameter settings.

Sure glad you got your new lathe up and running! Enjoy!

 

[Ischgl99]

Or if the resonant frequency changes due to variance in load. He was not having issue at speeds in idle. So I wonder how will it do on variating loads. But I guess it should be fine.

Tim

The resonate frequency of the belts changes based on tension, so if the tension changes based on load, then there could be a change in natural frequency. The way he was testing this, I don’t expect there would be much of a change in belt tension, if at all. What I think happened is, if the exciting force is torsional, like I suspect here, then a light inertia of just the splined input shaft and gears won’t be able to excite the belt resonant frequency since the dampening of the belts without the spindle connected is large enough to overcome the inertia of the small shafts and gears. Once the spindle is connected with the motor, the dampening is significantly lower than the inertia of the shafts, gears, chuck, etc and it can no longer dampen the torque pulsations caused by the VFD.

 

[CarlK]

I'm skeptical that the lathe was sufficiently tested prior to shipment. All you did was put it in high gear and run it up to 700 RPM to get that horrific noise. Unless VFDs can change their settings during shipment, they couldn't have tested it.
I'm very happy that you solved it.
IMO product support is not what it should be. I bought a new ACER Bridgeport clone some years ago ($12K) and heard motor bearing noise. I was able to convince the tech I spoke with by holding the phone up to the top of the motor.
They sent me a whole new motor and I had to do the change myself and return the old one. Never did anything like that before. Other than that it's a nice machine.
The only option we have when we don't get good support is to complain very loudly on the internet and try to shame the manufacturer into resolving the problem. Fortunately it didn't get that far in your case.

 

[Sticks]

...
The only option we have when we don't get good support is to complain very loudly on the internet and try to shame the manufacturer into resolving the problem. Fortunately it didn't get that far in your case.

Well...the OP is a lot more patient that me. $20k of personal money and it is effectively DOA...After I made arrangements to get it unloaded, cleaned up, and moved into my work area?!?

2 weeks tops, and that is phone calls (plural) every single day to either get it resolved, have a professional come out on their dime to fix it, or have it returned on their dime, including any additional resources to get it back out to where it was unloaded off the first truck, and a replacement on it's way.

About the second time I am told that "We are waiting to hear back from the factory" then I am in orbit.

 

[tim81]

Well...the OP is a lot more patient that me. $20k of personal money and it is effectively DOA...After I made arrangements to get it unloaded, cleaned up, and moved into my work area?!?

2 weeks tops, and that is phone calls (plural) every single day to either get it resolved, have a professional come out on their dime to fix it, or have it returned on their dime, including any additional resources to get it back out to where it was unloaded off the first truck, and a replacement on it's way.

About the second time I am told that "We are waiting to hear back from the factory" then I am in orbit.

Hahahahahaha