I'm lost

Hi jawiest, the main problem with your model is that at every place you have curves meeting up they are not tangent smooth to each other, they have a slight crease:





This kind of thing where curves are not smooth to each other but only a little ways off makes things difficult for filleting. So the main thing to do for your case here is to improve the quality of the curves before you extrude them. The curves need to have their first 2 points in line with the first 2 points of the next segment so they are tangent to each other instead of slightly creased at each place that 2 segments are touching.

- Michael

Another problem is you have some fillets of a smaller radius than 0.25 already put in. Don't do that, put in largest radius fillets first and then smaller radius ones later.

Otherwise you create a situation where there is not enough space to fit your fillet as it goes around a bend that is tighter than the fillet radius.

- Michael

Hi jawiest, in the attached version I tuned up your curves so they were all tangent with each other
by editing the points and placing the last 2 points of each curve to be in line with each other
so the curves were tangent:



And I also removed spots where you had a bend tighter than radius 0.25 in your curve setup.
If you try to make a fillet that is larger than the space available for it to fit it will get bunched up like this:



So if you intend to make a fillet of radius 0.25 do not make any rounded areas in your profiles that are
smaller than radius 0.25 because when you then try to make a fillet of radius 0.25 going through
that area it won't have room to fit there.

With these things tuned up you can now fillet it:





Hope that helps!

- Michael

Thank you Michael for your help it's people like you and the others that make this fun to use.

John