Hi mk1978, thanks for posting your file.
So it looks like the problem with filleting your shape on the right is that you have 2 loft sections that have sharp corners in them:
Then for the top profile curve of the loft it has a different shape, there the curve segments are smooth to each other instead of sharp like the lower 2 sections:
This is not a good situation for filleting, basically because a fillet is something that goes on a sharp edge.
Check out this example here where I've got 2 surfaces that vary in angle to one another, starting at 90 degrees to each other and then progressing to being almost smooth to each other:
If you make a fillet between there it will look like this:
So note there that the fillet starts out wider and then gets narrower and narrower as the surfaces become closer to being tangent to each other. If the surfaces became completely smooth to each other then the fillet would shrink down to 0 width at that spot and that makes things a lot more difficult for the fillet construction.
Also that above is not what is called a "variable radius fillet" - it's a constant radius fillet. What is changing there is the length of the arc for that spot in the fillet. They are all arcs of the same radius, just some are long and some are shorter length arcs. Here is another example this time with curves showing how it works as you go from a larger angle to an almost smooth angle. These are all the same radius circle but you can see that the piece of the circle that will be used gets shorter as the tangent directions approach being smooth:
Then there's also a fillet mechanism called "variable radius" fillets - that's where the radius of the fillet arc is also changing as you travel along the fillet. That will also make for variations in the width of the fillet but in a different way.
So for filleting to have a better chance to work well you would want to avoid this kind of "sharp segments, sharp segments, smooth segments" progression between your loft profiles. If you had made them all the same sharpness like your ones in the middle, then you would be able to fillet it ok:
- Michael
