Trying to diagnose induction motor buzzing

[AndySomogyi]

Andy - when you do go to the point of electronic gearbox, you will find there are always several ways of achieving an end result. For example, most controls are devoted to feedback control of speed first, using encoder pulses from the motor shaft. Provided you have some way to account thread backlash, you can get to position control with software by counting pulses up and down, if started from a known parked reference.

Deriving speed control from rate of change of position is worse than deriving position from integrating speed.
The best way is to let the shaft encoder control speed, acceleration, deceleration, safety stop, torque limit, etc. and use a separate position feedback for CNC style position control. These are just retro-fit digital read-out kits, now much more affordable, modified to allow motor control electronics to use them for position feedback.

The small motor you would use to drive (say) the lathe carriage can then be programmed to (say) cut a thread, in concert with the motor driving the cross slide, to make the thread from start to finish, including taking progressive cuts, and a finish cut.

The really clever nerds sample the tool position at some high frequency, and cut compound curves. I am not actually into CNC projects myself. I just play with the great old machines, but I have seen what can be done with things moving in precise relationship, where previously, they had to be geared together.

Hi, my electronic lead screw is basically Jame’s screw here, he has all the source code developed, so I’m basing mine off his work. He also has the interface boards to hook up the microcontroller to the steppers, for like $15.

It’s a TI microcontroller that’s extremely capable, so lots of cycles left to control things besides lead screw.

I’m not going full on CNC yet, just sort of a half way approach, but I’ll pre-define certain things likes tapers, radii, steps, things like that.

My day job, I’m a research engineer, develop finite element modeling software, and build laboratory instrumentation electronics. But my real interest is cars, building a Subaru swapped 76 Porsche 912.

If you guys need any help on the math / physics / mechanics side, or automotive questions, I’m glad to help with whatever I can.

Sent from my iPad using Tapatalk Pro

 

[mksj]

Problems with one motor doesn't tell you much about the company and other motors they produce, it is unclear if the problem/noise was corrected and/or what represents the motor baseline. Everything is to a price level, it all depends on how much one wants to spend. That being the case, Dayton does produce some pretty cheap motors. I did look over you wiring notes and the connections seem to be correct. Partial shorting of the coils would not be detected with standard ohm meters. A 3 phase motor would be a more ideal choice for the lathe and a decent quality 2 Hp can be had for under $300 if you shop around. Get an inverter type if you plan to use a VFD, otherwise an RPC may be an alternate option. Single 3 phase machine I would suggest a VFD.

 

[AndySomogyi]

Problems with one motor doesn't tell you much about the company and other motors they produce, it is unclear if the problem/noise was corrected and/or what represents the motor baseline. Everything is to a price level, it all depends on how much one wants to spend. That being the case, Dayton does produce some pretty cheap motors. I did look over you wiring notes and the connections seem to be correct. Partial shorting of the coils would not be detected with standard ohm meters. A 3 phase motor would be a more ideal choice for the lathe and a decent quality 2 Hp can be had for under $300 if you shop around. Get an inverter type if you plan to use a VFD, otherwise an RPC may be an alternate option. Single 3 phase machine I would suggest a VFD.

I do think I’ll probably replace it with a 3-phase motor, I’ve found a number of Baldor 1.5 hp 3-phase local really cheap, and a VFD is only like $85. My mill has a generic Chinese 3-phase motor on VFD and it is SOOO SMOOTH! I never realized how rough single phase motors were until I used my mill a lot.

I’m guessing a smooth motor is even more important for a lathe, as vibrations will get transmitted to the work and negatively effect the finish.

 

[AndySomogyi]

Turns out that I did wire the motor correctly, and all the noise and vibration were because it was a very poorly made and finished motor. So, just to get the lathe going, I mounted the motor on these rubber vibration isolation mounts I got on Amazon for $14. Wow, what a difference. Here's the motor running, compare this agains the previous videos. You can still hear it running, and still feel a big of vibration in the bed / tool post, but hoping this vibration doesn't cause any surface finish issues.

if you watch this vid, interestingly enough Ike the cat makes more noise than the motor on these rubber isolation mounts.