Re: [CAD_CAM_EDM_DRO] More on Re: Insulating D-shell from chassis?

zephyrus@... wrote:

>To the best of my DVM's ability, the potential between the PC chassis and
>driver box chassis is .000V; the potential between the driver box chassis
>and its isolated DB25 shell is .000V; and the potential between the PC
>chassis and the isolated DB25 shell at the driver box is .000V. Both PC
>and driver box are using switcher power supplies. The DC ground of the
>driver box is not connected to chassis ground (unless it is through the
>Xylotex board...)
>
>The spindle motor is a Sherline permanent-magnet DC motor with their drive
>electronics (KB Electronics KBIC PWM driver.) I always turn the speed knob
>down all the way before switching power to the spindle. The spindle drive
>is not under G/M code control at all.
>
>The random steps were only while the spindle motor was running--I could
>feel them by placing my fingers on the handwheels on the stepper motor
>backshafts.
>

Ah HA! Now, that is the most important data you've given yet! Som why are
you hacing at the computer-driver connection, when you KNOW the problem is
the spindle drive?

I would make a first guess that the spindle drive is conducting EMI onto the
power line. If you can come up with an interference isolator (often used as
part of a power input module on high-end computer and instrument gear)
and put it in the line to the spindle drive, i bet it will clean up the
problem.

If not, then you may need to filter the output of the spindle drive, or
make sure
the spindle motor is well isolated from the machine frame.

Jon