its a dyna mechtronics DM2900

im posting in general because i think this issue is pretty common..tuning a spindle PID amp correctly

the spindle amp is a B25A20 from advanced motion controls

the problem is two things:

-during spindle orient, it orients correctly, but it "rings" when it reaches its final location, oscillating back and forth about 1/16" an inch until it finally settles. the ringing always dies out, but it takes a few seconds.

-at rpms below about 1000, you can hear lots of electrical "noise"..i.e. the acoustic noise generated by the spindle amp interacting with the motor. its not worn out bearings or actual mechanical noise..the motor is acting like a speaker

-i have limited experience with machines like this..the only other machine i have used that could orient the spindle was a fadal and it was silent..so im suspecting this ringing and noises arent normal, and im concerned they will cause problems during rigid tapping or low rpm operations

-the control allows you to modify the PID parameters directly, i.e. kp, ki, kd, dt. there are also settings for spindle acceleration and encoder resolution. everything is set to the factory defaults. i dont think anything is way off because in general it all works and the rpms are correct (ive verified with a scope), its just not tuned very well

-i tried modifying the PID constants but i can only get a marginal improvement

-the motor is a 6000rpm with three connections for power, it has an encoder.

-the spindle is driven via a belt which looks to have a ratio of about 1:1.5...7000rpm spindle speed at around 4500rpm motor speed i believe

any ideas? is there a way i can tune things so they are silent and perfectly smooth, or is that unrealistic?