Dear Frenchy Pilou!
Of course, I KNOW I need to combine 2 of the object before doing fillet.
The file I have deliberately left them separate.

Dear Michael, I do exactly as you - but it turns out like the picture ...
One of the small pipe was really not the solid.
Apparently accidentally left after my unsuccessful experiments

Hi krass,

> Dear Michael, I do exactly as you - but it turns out like the picture ...

That one you're doing is a more complex one since the fillet needs to cross over several different adjacent surfaces instead of all being contained in one single surface. That means there are several fillet surfaces that will be created, not just one like the other spots.

There also seems to be a little bit less space on that one, 0.6mm just barely does not seem to fit.

A 0.5 radius looks like it will fit but it seems to get confused and still only build the big portion - this will probably need some low level surface/surface fillets to finish it up since the edge filleting is having a problem. Surface/surface filleting is when you have 2 separate surfaces and you select those 2 surfaces (not edges), and then run fillet, it can work in situations where the regular edge based filleter gets confused for some reason. I guess it's probably confused in this case with something about the seam edges.

- Michael

rotate your cylinder object 90 or 180 degrees in the back view before doing your work.

Thank you very much, I will try to follow your great tips!

Hi krass - I'm not entirely sure but I think that the problem might be a very slight (like maybe just 1 or 2 degrees) tangent difference between some of the large pieces. Even just a slightly sharp area means that fillets do not naturally have their ends aligned. When I do surface/surface filleting on those the fillet ends are just slightly off from each other and that usually should only happen on slightly creased things.

Either that or maybe some bug in filleting related to handling fillets that cross over the seam edge of a closed surface.

- Michael

Seems to be something going wrong with the fillet crossing over the closed surface seams.

I've attached a version here with those edges filleted at 0.5mm , I rotated the main tube 180 degrees in the Top view around its center point, to move the seam edge off to the other side where it does not run right through a small tube. After that I was able to make the fillets.

- Michael