Hi,
I can find some documentation about the SEM30 and Norwin drives, but doubt the models I've seen are indentical to yours but none the
less can well imagine that you wish to retain them if they are in working order. That would require an analogue output controller.
As you say CSLabs do a nice unit but around $600 and Vital Systems also have a good reputation but their analogue ready controller is $1200.
Galill is really classy gear but three axis analogue around $2000.
An ESS by Warp9 (step/dir) is $180. The difference between the CsLabs analogue and the ESS is about $400, still not enuf to replace the servos
certainly with AC servos but you may find that good sized steppers and drives can be had for that budget.
My concern would be 'what happens if one of the Norwin drives craps out?' Can I repair it? Could it be replaced and how much? So there is a risk
in retaining the old servos and drives over and above the premium paid for an analogue controller.
Price two 34 size low inductance steppers, big suckers, 800 oz.in or better, 72V supply and two AM882s. When set up properly they should not lose steps
and will be quick if not as fast as the servos they replace. You may like the idea that the smart drives can overcome lost steps but if you are pushing steppers
to the extent that they start losing steps then its probable that the drives will throw a 'following fault' error. Don't be taken in by the advertising hype.
Craig