Thanks for the reply. And the lesson learned about failing at two different levels. Michael, I had already tried half of your solution before posting here. However, I was still using the `fitFillet` command. It worked sometimes and sometimes it didn't. I'll try the idea with the `blend` command later.

That works very fine. Like Always. Thank you Michael, very much!

Hi,
I'm having trouble with a new filleting.
Goal: The transition from the channels to the lens should be smooth/slightly rounded. Why am I unable to achieve this?

Hi mala, the initial problem is your model is made up of individual surfaces, you need to get it joined together so edges are shared instead of everything being separated.

- Michael

Hi Mala, it looks like the separate surfaces problem is caused because your dome shape was an open surface instead of a closed solid when you did the boolean on it.

You should make the dome into a closed solid before doing the boolean. You can do that by selecting it and running the "Construct > Planar" command which will close off the bottom with a planar surface.

Additionally the cutting objects have a little gap in the middle area, they are also not solids. I closed those up by creating some lofts and joining those in.

- Michael

Hi Mala, in the attached model I've fixed those problems.

So you should be able to open up the attached version, select these 22 edges:



Note don't forget this little one here:



Then you can apply a fillet:



It is helpful to refer to the "object type indicator" here to know if your
selected object is a finished solid or an open surface:



- Michael

Hi Michael, thanks for eliminating the design flaws! I learned from them, replicated them in the design, and also added it to my personal MOI wiki.
Best Mala...