Basics on control and positioning with stepper motors

[richard2112]

Hi. Can I just ask a few basic questions about control and positioning with stepper motors employed CNC machines, linear actuators (gantry type or otherwise).

I think most people here make CNC machines. Okay here are my questions:

* Are you accelerating and decelerating the stepper (ramping up/ramping down the step frequency). Or, are you operating the stepper at the maximum starting frequency (fs) to get "instant" start and stop?

* To get an accurate stop position, are you programming (via a counter, or whatever) the number of steps to the stop position? I suppose you must be with open loop.

* Is braking used?

* Do you find it necessary to use open loop with the stepper motor?

Thanks.

ADDING: The thing is, I'm not seeking to build a CNC machine as such. So, my technical requirements might be somewhat different. Just wanting to grasp what the CNC machinists are doing, as it's not a million miles from what I'm trying to do.