The machine is a R2E3 Boss8 Series II, with SEM servo motors, and Heidenhain ER-120 encoders stock.

This only concerns the Y axis. I realize now this problem started a couple years of years when I was
engraving at probably around 1 or 1-1/2 ipm, I noticed a "rude sound" only when the Y axis was moving.
It was kind of a buzzing sound. I thought it was odd, but I did not see any problem with the engraved
pattern so I let it go.

Then 2 months ago I was using the jog wheel to move the Y axis while indicating a diameter. When
I moved the jog wheel fast there seemed to be no problem, but when moving it slowly I would hear a crunching sound that was absolutely horrible sounding, kind of like you might imagine a destroyed bearing to sound like. When watching my indicator, and slowly moving the Y axis using the jog wheel I could see
the Indicator needle "buzzing" in the range of about plus and minus .002 to .003 (.004 to .006 TIR.) When I stopped moving the jog wheel the buzzing would completely stop.

Then just last week I was cutting a 4 cavity "o ring" mold, with approx 7/16 OD and 5/16 ID using a 1/16 cutter. During setup the crunching showed up again. Then I ran the roughing PGM at about 1-1/2 to 2-1/2 ipm with no problem. Then "on the finish pass!" the crunching started, and by manually speeding up the feed with manual override I was able to get axis motion to smooth out, but not before leaving unacceptable gouge marks on 2 cavities.

Has anyone out there experienced anything like this on their Boss8 or Boss9 Series II (or Series I) machine? And maybe fixed this problem? I know I could swap x and y motors to help isolate the problem, but I'm hoping this sounds familiar to someone, before I have to take that action.