rodw wrote: Yeh I think so but now with your help it is now relevant as it shows how to calculate the heading (Tangential direction) to orient the knife. (And even the arc radius if thats required...)
But, it would do it too late for a tangent knife which needs to lift on sharp corners.
This really is something best done in the CAM system.
However, it is not too hard to imagine doing it with an input filter.
Here is an example that changes input g-code to use inverse-time feed mode:
forum.linuxcnc.org/38-general-linuxcnc-q...r-me?start=10#120524
A (very) similar filter could lift and align the knife prior to each G1 move, simply lift the knife before each G0 and insert a rotary move into every arc move to roll round the curves.
