[drumsticksplint]

Hi guys,

I've recently bought a small cnc lathe, really nice machine with very little use (it came from a school) The machine has parker DC brushless motors and drives (BL30). I powered the machine up and everything seems fine, however, the other day I noticed that the X axis has developed a "judder" type effect when moving. The Z axis is fine, movement is very smooth. I have downloaded the manual for the parker digiplan BL30 drives and it states in the troubleshooting section that adjustment of the "time constant" and or the "damping" pots should cure unstable motor operation. I have adjusted both pots in various configurations and I can make the problem worse, but not totally cured. When stationary, the X servo "flutters" slightly back and forth, this can also be noticed in the dro of my control. I have examined the mechanical aspects of the axis and all seems to be free and smooth when operated by hand, the problem it seems resides in the motor / drive. I seem to be able to almost eliminate the problem with fast movements but the problem is worse when moving slow, or vise versa.

There are also 2 other pots on the drive: "balance" and "tach gain", I haven't touched these as of yet.

Any pointers would be usefull

Thanks

[hub]

It sounds like a tuning problem to me. Yours have pots only? Try adjusting the balance & gain too. I would start with the gain.

[drumsticksplint]

Yeah pots only, the machine is circa 1998, so its a bit old, but hardly been used! I thought it was a tuning issue, I'll have a play around with the other pots tomorrow and see if I can make any more sense of it. Maybe something moved slightly when the machine was being transported.

Thanks!