Quote Originally Posted by mactec54 View Post
No you do not need an external Encoder, even if the drives are completely power off the Encoder will remember where it is at for up to 45min even without the optional battery powered backup
Maybe with the absolute encoder option. I have no experience with that. This has not been my experience with the incremental encoder. The external encoders that I was referring to are linear encoders on the table, tied back to the controller. The only time that position is lost is on a computer power down.

And the servo motor can never run away no matter how it is wired up, they have a safety feature that will prevent any Encoder fault or motor run away
I had the runaway problem when I had the DMM logic powered (and stable) before energizing the DMM main power contactor. Many times, but not always, the motor would make up to about 50 uncontrolled revolutions at full speed before stabilizing. This problem ended when I wired the DMM logic to the main power contactor for that drive. The good news was that in that particular application, the motor could run freely without any danger of damaging the machine, unlike a machine tool with limited travel.