Hi Anis, I was able to complete the fillet using surface/surface filleting:



The filleted portion is attached as fillet_completed.3dm - that is just these few surrounding surfaces, you can join it into your full model by deleting those in the original then doing a File/Import and then a join.

One of the surface/surface fillets would not generate, I'm not sure what was wrong there I'll see if I can take a quick look. But since this part is symmetrical it is only necessary to generate the fillets on one half and then mirror them over to make the full fillet - that's what I did to complete it.

Also after each surface/surface fillet, I copied the resulting fillet using Ctrl+C and then undid the messed-up trim, then pasted the fillet back in. Then I only did the trimming once I had all the fillet surfaces in place.

I probably should make an option for turning off trimming when doing surface/surface filleting.

- Michael