Hi,
I haven't used Mach3 for nearly three years having migrated to Mach4. Having said that the similarities between the two should
be sufficient for you to implement a strategy in Mach3.
The first consideration is whether you require your spindle to be capable of coordinated motion. This would be required for
rigid tapping. Coordinated motion requires not only velocity control but position control. Position control can be achieved with analogue
controllers as I posted earlier....but at some extra cost and complexity.
Given that your motor is a servo it can of course be operated in step/direction mode to achieve position control. This would mean that you don't
require one of the more expensive analogue controllers. I am unsure of the exact details of how you implement step/direction control for a spindle in Mach3.
I am more familiar with the idea in Mach4. The trick here is that a free running spindle, which is its normal mode of operation would require a step
signal accumulator of infinite size so the spindle can keep rotating without numerical overflow. A position controlled spindle for rigid tapping might only
rotate 20 turns in one direction and then unwind the same 20 turns in the other direction. I have got my high torque spindle to do this, its an Allen Bradley
1.8kW servo motor.
It took considerable effort to get both modes of operation to work, namely the free running spindle mode and the 'C axis' mode. Guess what....I don't
really use it. Because it was possible I thought I would do it only to find it was pretty much a waste of time. Sound familiar? It happens to me quite a bit.
99.999% of the time all I require is a free running spindle. This is much simpler and I would recommend it as a first step in your spindle control
evolution.
In Mach4 there is the possibility to have a free running spindle running in step/direction mode. No extra hardware required. Just fill in the required settings
and away it goes. If memory serves Mach3 can do the same, see the attached pic.
Another choice that achieves the same result is to use the servo in analogue mode. Just about all AC servos allow the possibility to use a +10V to -10V
analogue voltage to control the speed of the servo. In which case you can use an AC servo in a manner very similar to a VFD controlled induction motor.
Thus you have two choices to control a free running spindle with an AC servo:
1) Free running step/direction mode as provided by Mach
2) Analogue voltage control using Mach and your BoB to produce the control voltage and program your drive to be analogue velocity controlled.
If you require either an indexing spindle or a coordinated motion spindle that's a whole bunch harder. Would recommend you stay away from this until
you have had some experience controlling your spindle in free running mode....then maybe think about it!
Craig