Have you tried RoboDK?
https://www.robodk.com
Among other things, you can convert CAM programs (such as cartesian G-code or APT source) into robot programs for robot milling for example. The rotation around the spindle axis is managed automatically to successfully accomplish the path. Here is an example:
https://youtu.be/vznZiQKRdKQ?li…f3TFXEa56XNR1-m
I might be biased as I work at RoboDK, however, it is an active project and quickly gaining new customers.
It is by far the most affordable and versatile solution right now, offering an API and many examples.
...all the products listed in this thread cost $15,000US or more and they are process-specific, like milling or cutting.
You can try RoboDK for free:
https://www.robodk.com/download.php
We have a library of more than 200 robots. If your robot is not there we will add it at no extra cost. We also take our customer's feedback seriously for future updates.