Hi,
yes you are advised to separate your VFD wiring from signal wiring. This is a strategy to reduce RADIATED interference but does not address CONDUCTED interference.
You say that you have your VFD in separate 230V outlets but what degree of electrical separation is there between the outlets?
In New Zealand at the current time in the province in which I live there has been a major upsurge in agricultural irrigation much powered by multi hundred kW
VFD pumps. The electrical noise which is reflected into the power grid is causing major issues. The local power companies are having to insist that line reactors and
filters be used. The farmers hate it, line reactors and filters can cost tens of thousands dollars.
Small VFDs such as we use are not likely to come under official scrutiny but they do 'pollute' the electrical supply in their vicinity. My suggestion relates to the fact
that many hobbyist CNCers pollute their own power supply and then wonder that their sensitive electronic systems go cranky.
Try running your VFD, or alternately your machine controller/PC, from an extension lead well separated (physically an electrically) from the other.
I have given similar advice to others and about half have found that it solved the problem. Some have gone on to buy line reactors per VFD manufacturers recomendations
to achieve a permanent solution.
Conducted electrical interference is often overlooked. You could spend many hours and dollars trying to stop radiated interference and achieve nothing. Try the conducted
noise experiments until you are 100% positive that it is not the fault before trying the radiated noise reduction strategies.
Craig