Siemens NX (Unigraphics) Users

Extend the left side of the arc a little. It may help.

THE SAME PROBLEM PREVAILS.. BUT IF I DO SO THE PROFILE WHICH I REQUIRE CHANGES NA ANY WAY IT DIDNT WORK..THANK U PAUL

I would make a closed sketch and try instead of open loop

Make sure your arc is tangent to a horizontal line extending from the top of your cylindrical boss, or above that line. Else, it will fail.

thank you dude yeah IT WORKS I COINCIDED B4 by creating an intersection point , after creating a reference line and making in tangential getting the profile

Yes the 'rib' feature is a bit finicky about that. I've had designs where I needed the arc tangency below the point of coincidence in which I resorted to cutting it with a surface. Such is the CAD part of design... always with a new challenge to get the desired result.

Glad I could help.

i see ur picture u have missing few lines so cannot create the rib. but sometimes this rib feature in the relationship is very critical / tricky.