Hi torsten, yeah probably the edge-based filleter will have difficulty trying to put a fillet on edges that run into such a combined thin and also simultaneously pointy area like that.

You will probably need to use an alternate mechanism for modeling the smaller rounded parts, maybe constructing a rounded sweep surface, or cutting some area away from each side and using Blend.

You also might be able to use surface/surface fillet for building a fair amount of the needed fillets. Surface/surface filleting is when you break your model apart into individual unjoined surfaces and then select 2 surfaces at a time and then do the fillet. That generates the fillet in a somewhat different way that is calculated more directly between each surface instead of tracking along edges like the regular edge-based fillet will do.

The surface/surface fillet does not do things like deal with corner junctions where multiple fillets are running into one another - that's one reason why it can generate stuff in areas where the edge based filleter will have difficulty though.

- Michael

Another thing is that on the all sharp edges one you may be able to get the fillet to work if you fillet everything instead of trying to leave the knife edge unfilleted. That will make a weird result but you can then extract the fillet surfaces that were created by selecting them and using Ctrl+C to copy them, then undo and then paste them in, and that can give you some rounded section pieces to work with, you would still need to fill in some areas and do some manual trimming to get them into place then.

- Michael