Hi Tony - your new version looks to be more cleanly constructed.

I just loaded it and I can fillet it over here ok by just selecting the entire object and then using a radius of 0.01 units:




What fillet radius are you trying to use, are you possibly trying to use a value that is too large? Your model is made up of a lot of pretty thin pieces, so there is not enough room for fillet much larger than 0.01 to actually fit in the available space on the model.

If you examine the result of the 0.01 fillet you can see that it is still having to put in some fairly complex corner junctures in some areas like this area here:




That's happening because your model is not smooth in that area - it looks like your original curves come to a sharp but somewhat shallow corner in there, if you zoom into your model in that area you can see this:




That kind of "sharp and shallow" feature of the outline is not so good for filleting, it makes the filleter do a lot of extra work in those areas. It's better for something like that to be fully smooth or more distinctly sharp instead of just slightly sharp at a shallow angle like you have it now. In your particular case here it was just sharp enough to allow it to be filleted ok, but that's still an example of the kind of thing you want to fix up in your original curves before you actually construct solids or surfaces out of them - having your original curves be higher quality and smooth in areas like this will then make filleting of things constructed from them later on go a lot better.

So there are still some aspects of the model construction that could be improved even more.

But anyway, the model you posted does seem to fillet ok over here just as long as you ask for a small enough radius that will actually fit in there.

- Michael