Hi,
most servos, and I'm assuming yours is an example, can run in multiple modes. The two modes of potential use as a spindle are analog velocity mode and position mode.
Of the two analog velocity mode is the easiest to understand and implement in Mach3.
If you program your servo drive to analog voltage mode then the servo rpm will be linear from CW velocity max to CCW velocity max with an analog input voltage from +10VDC
to -10VDC. If you already use Mach3 then you probably have a relay to turn the spindle on or off. Use this relay contact to Enable or Disable the servo drive. The PWM output
of the controller is likely 0-10VDC, or you need to make it so, and that would give you linear speed control of your servo from 0 rpm to velocity max.
Your servo now behaves like a regular VFD controlled spindle. Easy.
I have a 1.8kW AC Allen Bradley servo as a spindle motor and I use it in this manner a lot. It has so much more torque than my normal 800W 24000rpm spindle so I can use it with larger tools,
say 16mm diameter, in steel and stainless.
Occasionally I use the Allen Bradley in position mode, ie Step/Dir. This means that the spindle is a C axis and can be coordinated with the remaining axes and in particular I can do
rigid tapping. I thought I was being real clever when I dreamed this up, and it does work, its just that I don't use it that often. When I do use the Allen Bradley spindle 99% of the time
I use it as a free running spindle, ie analog velocity mode.
May I suggest that to start with you try running the servo in velocity mode, it is the easiest solution with most Mach3 hardware. Once you get that working properly then you might start thinking
about position mode and a genuine C axis.
Craig