[dazp1976]

@mactec54 curently the spindle works at program S speed irrelevant if the feed rate is full or decreased. I am looking for a solution to obtain a reduction of the spindle rpm when the feedrate is lower due to corners. Either controller or program, it does not matter how i obtain this. But as @dazp1976 says, the S will not change on the fly, and the axes will stop to adjust for the S, which makes the situation worst.
Ideally what I need is a way to have lets say
10m/min feed rate and S 20.000rpm wehen in straight line
and
S 8000rpm when feed rate goes down to 4m/min as it goes through a curve and axes need to slow down.
And if the corner and precision requirement are tight and feed rate must go lower, the S should not go below 5000rpm.

I am a bit surprise to find such little info about this option in online sourced. It goes along the concept of constant removal rate, and should be easily achieveble as an interpolation of spindle with the other axes.
As I said when I cut plastic I see that higher rpm makes nice cuts on straight line cut burrs in corners, lower rpm nice corners but spindle is struggling in straight line.

Can you just cut it 'normal' or faster but this time leaving say 0.2mm+ on the stock (roughing).
Then run a 'slower' pass all around it at full depth right at the end to remove the left on material. (finishing).
That will prob work.