[adrian5]

Okay. So I think we're not in the same page with respect to where the problem is, but let me provide some more detail.

The spindle is an UgraCNC (Chinese) 2.2kw, water cooled model.
The VFD is a Fuji Frenic-Mini.
The Frenic's connection to the G540 uses three wires. On the Frenic these connect to terminals 11, 12 & 13. On the G540 they connect to screw terminals 7, 8 & 9 on the bottom of the unit. On the G540, 7 is ground, 8 is signal and 9 is V+. On the Frenic 11 is Common, 12 is Signal and 13 is V+ out.

Frenic 13 connects to G540 9
Frenic 12 connects to G540 8
Frenic 11 connects to G540 7

This all seems fine.

The G540 connects to the computer with a 25-pin parallel cable. Mach 3 configures how each of these 25 pins is to be used.

The CW spindle relay is, by default, on Pin 17. The PWM signal for spindle speed is, again by default, on Pin 14. Pin 14 appears from the documentation for the G540 to be the right pin to send PWM signals for it to interpret and convert to a scaled voltage to output on screw terminal 8. But that wasn't working.

After the aforementioned effort (see first post), it seemed like against all probability the G540 was listening on Parallel port Pin 17 for for PWM to derermine spindle speed, instead of the expected Pin 14. And when I configure Mach that way it does sort of work (pulsing issues being the "sort of"). This doesn't kmae any sense based on everything I've read.

I'm really trying to figure out what's going on, here.

-Ben

Could you please send me the settings you have on frenic mini to run this spindle?
thank you om advance