Servo Tuning Troubles

Hi.
I have built a nice DIY CNC router with much help from ebay.

However, I have run into trouble with the servo tuning stage, to the
point at which I have just ripped a metal flexicoupling in half :(

While tuning the X axis, I have seen the commanded move of approx 50mm
take place ok, then the servo threw itself into reverse at max speed
for a seemingly random distance. This ultimately saw it charge through
the limit switches and rip the coupling in half.

The Y axis seems unable to move at all, each time flagging 'Position
Error Exceeded'.

The only axis that is behaving is the Z axis.

Sorry if this is a bit long, but any suggestions would be gratefully
received.

Many thanks,

Richard

email me at novacustard@here

where h e r e can be replaced by yahooDOTcoD O Tuk



Servos, drives, controller and software are all Parker/Compumotor,
Controller is a Parker 6K4, all connecttions are by ribbon cable or
power cable where necesary. (Not shielded).

X axis is an SE230AE with 10:1 gearhead and OEM770T drive with 75vdc
p/s and THK44 Linear Actuator with 1 rev to 20mm leadscrew and 500mm
travel.

Y axis is an SE230AE with 10:1 gearhead and OEM770T drive with 75vdc
p/s and THK33 Linear Actuator with 1 rev to 10mm leadscrew and 200mm
travel.

Z axis is an SE232BE direct coupled to unknown Linear Actuator with 10
rev to 25.4mm leadscrew and 200mm travel. OEM770T drive with 24vdc supply.