Hi naoky, yes unfortunately that will not be unusual to have problems filleting text.

Text characters tend to have a lot of sharp angles, narrow regions, and tight bends in them - those are exactly the kinds of things that create difficulties in filleting. For a fillet to be successful it needs to have enough space for the fillet to fit, and things meeting at sharp angles tends to make difficulties with calculations and intersections of extended parts.

Filleting in general is a complex area that involves many functions such as surface offseting, extensions, and intersections so it is fairly easy for it to get messed up when there is difficulty with any one of those steps.

Probably several of those characters will fillet at a smaller radius value though - usually smaller radius values tends to avoid some problems. So for example I tried the Arial w character and was able to fillet it at a radius of 0.05 .

MoI's filleter is not generally strong enough to handle all font characters, if you need to fillet some more difficult things like that you may need to use one of the more "heavy duty" programs such as SolidWorks, Pro/E, etc...

I should be able to fix the original problem you reported earlier though, it turned out to be 2 bugs and I've nearly tracked them down.

- Michael