Re: CNC Conversion - which path to take
I'm a little confused here, are you wanting to retrofit a milling machine or a surface grinder? Or both? The two machines are really controlled differently from a functional standpoint. Same control hardware, but the G code would be different. A surface grinder could be set up with some simple step & direction controllers and some movable limit switch cams for the table travel, and a little relay logic to move the head down for the next pass. But this would be more complex than simply using some off-the-shelf CNC software, and standard G code.
There are a number of inexpensive CNC software/hardware options; Dynomotion, Centroid Acorn, or Mach3/4. Any of these would be compatible with closed loop steppers or step & direction input AC servos.
From here, the options are endless and are increasingly expensive up to crazy expensive. It is possible to use battery backup absolute encoders to always know where the position is, even after power down. But this gets into the crazy expensive area.
Jim Dawson
Sandy, Oregon, USA