Interference?

Hi Folks.

Yesterday, I changed the motor driving my milling spindle. Originally, I had an AC 1/4HP motor running at a constant speed of 1425rpm, with step pulleys to change the spindle speed.

I replaced this (perfectly good motor) with a DC Servo motor, with a variable speed control. The replacement motor is a Dynetic Systems model 318032, whilst the speed controller is a KB PentaPower Vari-Drive unit Model KBM240.

Immediately I started to use the system with the new motor in place, my stepper motors started 'twitching' and making erroneous movements, resulting in what should be, for example, a straight cut becoming a diagonal, with associated increases in the Z moves simultaneously. I can only assume that the new power unit is producing interference signals, which are affecting the control of the steppers.

What actions can I take to eradicate this interference?

Keith