We are having a few problems with our machine and outside interference, whereby the code gets interupted and then the machine loses where it is and does random plunges and gouges into the work, when looking through the code there is nothing wrong the code show exactly what it should be doing. The code itself has no bearing as to the movements you see on the table.
We have gone through the windows optimisation guide turned everything we basically can off and only have mach 3 installed on the computer.
The router itself is wired into the mains on its own power supply to try and eliminate any interference.
We have also earthed the machine to try and eliminate static.

The machine will run 3 or 4 days perfectly with no problems whatsoever, and then out of the blue the machine will have random acts of violence and chew through the work very unexpectedly.
Has anyone incountered this problem?? Or is there something else I might be able to try to help eliminate these random movements and interference???
Thanks for your help
Shelley

Try running shielded cable on the step and Dir lines... I think that will fix the problem

Step and dir cables are already shielded so not sure what it might be

What end did you ground? What ground did you hook the one end to? is there more than one shield in thecable? How long are the wires?