Cincinnati 15VC Z-axis following error

[jrice]

I have a older 3 axis Cincinnati vertical machining center that was retrofitted with an A2100 controller approximatley 14 years ago. Over the past 4 months I have been experiencing an intermittent z-axis following error. It occurs on a 3 axis move with a ball nose tool. The tool will drop suddenly and create a small divot in the part but the system will not alarm because the following error is not reached. Typically mid way through the next pass the z-axis drops once again and the system shuts down and a following error alarm is displayed. The part is typically a complete loss. I thought it may be a corrupt program but I ran the same section again with no problem but as it moved on to another part of the program the same problem occurred.
Any insight you can provide would be greatly appreciated.

Regards,
J.Rice

[cnc doc]

do you have manuals for machine if so refer to balancing an axis in either the bdf4 manual or a2100 manual sorry its been a while since i actually used a manual. also check your kv it should stay close to 2 at all times this can be adjusted and viewed at the control. second adjust the following error alarm limit so that it will not deviate far enough to damage part. you are lucky to get an alarm a lot of the a2100's would just stop in the middle of the program with no alarm when the following error became more than allowed.

[mike_Kilroy]

I agree you should probably be watching the gain/following error screen to see if Z is startinig to get erratic. sounds like maybe a motor problem but you need to start narrowing it down to component level. good start sounds like watch following error as you machine and see if it is erratic, jumpy - not at all, all the time, just on occassion?

15VC sounds old enough it may have brush motors still? if so this sounds like a tach issue starting but that is real wild far out guess since there is no data yet to decide from other than divot.