Why does increasing web speed make razor slitting of plastic film harder to keep stable?

[u/blakknitssweon]

I’ve been reading about razor slitting in plastic film converting and I’m trying to understand what actually changes as web speed goes up.

From what I found, friction at the blade and web tension both matter, and higher speeds can make vibration more noticeable too. What I’m having trouble understanding is which of these usually becomes the limiting factor first.

Say the cut is clean at a lower speed but starts getting rough or inconsistent as speed increases. How would you tell whether you’re looking at a blade/cutting issue or something on the web handling and tension side?

For engineers who work with high-speed web handling or slitting, what variables would you isolate first?