Hi, Ok I've made a few discoveries that may assist in getting to a solution.
In pcb-gcode the first pass is always one half the tool diameter away from the trace boundary. Successive passes are one or more stepovers away from that boundary. Compare that to how Fusions Contour works. If you specify a certain number of roughing passes, lets say 5, then the first path is 5 times the stepover away from the trace boundary. Successive paths get closer to that boundary with the final path one half the tool diameter from it, ie the trace is formed and isolated.
Fusion isolates from the outside inwards whereas pcb-gcode isolates from inside outwards.
Where Fusion is going wrong is that if it encounters geometry that it has to respect at the first pass then the toolpath describes a path that respects that geometry but was not in fact part of the geometry you intended but is a part of an adjacent feature.
As proof Fusions Contour works OK if you have NO roughing passes, or alternately the closest but separate feature is further than the number of roughing passes you have specified then it too works fine. For instance Fusions Contour works OK and predictably when either no roughing passes, or one roughing pass is commanded but at two roughing passes it fails.
At two roughing passes it encounters an adjacent trace, and it obediently generates a toolpath around both the trace that we hoped was to be isolated but also the adjacent trace.
By making this observation I can start to make sense of what I had previously considered 'garbage' that Fusion was generating. That does not in itself solve the problem, but at least understanding how and why a function is not performing as you want is as least a step closer to solving it.
The first thing I tried was to set a negative value for stepover for each roughing pass. Fusion refused. The idea was to have Fusion generate toolpaths from the trace outwards much as pcb-gcode does.
As I posted earlier in this thread pcb-code works by generating a tool path pass and the ADDING that pass into the geometry of the trace. Then it will generate a new and somewhat larger tool path using the enlarged geometery.
Could Fusion be induced to do the same thing? It seems for instance that if Fusion Contour does not use any Roughing passes it performs perfectly well. Could we therefore generate the first tool path then add that extra cut width to the geometry of the trace, and then generate a second tool path using the same
parameters on the enlarged geometry?
This would mean that Fusion would cut from the trace outwards and that replicates how pcb-gcode does it.
Craig