[Autonow]

I know this is an open ended question. But I am looking for the "best" hardware/Software for an Industrial lathe. I have the lathe and servos (existing Siemens) and I want to retrofit it with more mainstream controls. So what I am looking for is the most popular (means a lot of operators know how to use it) and most reliable (manufacture has lots of "integrators" who can troubleshoot problems). My only experience has been with GE Fanuc but I am sure there are others. What is Amada and Mori seki using these days.

When I say software I am not looking for design software but the software that operates the machine and loads and runs the gcode.

[Al_The_Man]

The fact you want to use the existing servo's are going to be a large deciding factor as many of the 'Mainstream' controls require integrating their systems as a complete package.
There are some that are still open to using other servo's and drives but they are getting fewer.
I would say among the top four are Fanuc, Mitsubishi, Fagor, Siemens.
But AFAIK, the only one that still offers open source for hardware is Maybe Fagor.
All of these offer factory support but you are better off to check in your area as to what systems are supported the best by service providers and retrofitters.
IMO If you are looking for a big name package for retrofit, then go with the whole package, it is often just as cheap in the end.
Al.