Hi Phil, also in some areas you've got some little tiny slivery surface fragments, possibly some remnant of some pieces being misaligned a little bit when cut with one another.

Here I've hidden all curves so only the solid and its edge are being displayed - it's subtle but notice that this area here looks a bit dark:



The edges are slightly dark there because there are 2 edges stacked up on top of each other there, there's a little squashed thin extra surface sandwiched in there, if I delete the big 2 adjacent surfaces there is this little weird piece left:



These kinds of little tiny squashed surface fragments will really mess up edge-based filleting. There is another kind of filleting which is surface-to-surface filleting, which is when you select 2 individual surfaces and run the Fillet command rather than selecting edges to fillet. That can sometimes be helpful for getting fillet surfaces to work with in areas where edges are messed up.

- Michael

Another thing that makes for difficulty with filleting is when 2 surfaces are fairly close to being smooth to each other but actually meet at something like a 5 degree angle. When surfaces meet smoothly then it also means that fillets traveling along that area will also meet up smoothly. When 2 surfaces meet at a sharp angle it means the fillet surfaces do not themselves naturally meet up end to end and instead need a corner juncture patch to be made. But when they are pretty close to being smooth the juncture piece may be some little slivery piece itself which things have difficulty processing.

Here's one such area along where you want to fillet that looks like it is not quite smooth but at a very shallow angle:




It would be a lot more "fillet friendly" if that was a whole smooth edge there, probably with those pieces being one single surface rather than 2 separate faces.

- Michael

Hi Phil, I've done some reconstruction work on your object and attached an updated solid version of it here. Basically I used some of the techniques described in the object repair tutorial (http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17) to untrim surfaces and retrim where necessary to backtrack and get your object as a full piece like this:



Then I got the side planes of the upper piece arranged like this:



Then I used those planes both to cut out the hole in the top for where to connect and also the same planes were then also trimmed to use as the connecting side walls as well, that way with a common surface used the pieces are better aligned and can be joined without having any slight misalignments causing problems. I also untrimmed the side hole and recut that as well.

I think this has eliminated the little slivery surface fragments and also consolidated a lot of the fragmented edges so filleting will have a better shot on this one. I just tried a fillet for the area you wanted, and it seems that for smallish values like 0.5 or 1.0 it is working there, if you need larger than that, then some of the "slightly creased" surface meetings are probably getting in the way of those working very well, let me know if you still need help getting the fillet part finished. Here's what a fillet of 0.5 looks like:





Hope this helps!

- Michael

Hi Michael,

Thank you so much for your help and patience. This looks great.

I also appreciate the link to the repair tutorial which I had not found during my searches (doh!). I'm at work at the moment but will look at everything in greater detail tonight.

As promised I will stop pestering you for at least a few days ;-)

All the best

Phil