Problem with cleanup fillet surface

This is my 2nd attempt to make a watch strap. I want to apply a fillet to the top part of model, there is a line extended in the bottom of the surface, tried to trim but failed, any idea?
strap2.3dm (427.2 KB)

Hello - was the goal to fillet all the way around or to have it taper off to a sharp unfilleted edge there?
One thing that may cause you problems is that on the original curve that you extruded the segments are not quite tangent:

Command: _Gcon
Curve end difference = 0.000 millimeters 
Radius of curvature difference = 3.343 millimeters
Curvature direction difference in degrees = 178.215
Tangent difference in degrees = 1.785
Curves are G0.

Also, I would extrude the curve a little longer than you need but not a lot longer than you need - the trimmed part you are dealing with should not be that much smaller than the underlying surfaces as a rule. ShrinkTrimmedSrf can help.


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Hi Pascal, the goal is to have a sharp edge at the bottom. I will check the tangent again as I create the that curve with Arc Tangent. Thank you.

I fixed the tangent problem, perform the same steps, but still the bottom surface have extended edge (the mouse pointer position) cannot be removed. Any advice? Thank you.

strap2-1.3dm (428.1 KB)

Edit 2:
I found a way to close the fillet, delete the bottom surface, then use extend curve, quick curve blend and sweep 2 rails to close the fillet.

But now I don’t understand why there are naked edges at the front of the strap, how to fix it?

strap2-2.3dm (425.1 KB)

Hi you can extract both bottom surfaces ( RMB on explode icon ) and run the Cap command

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Hello- here is how I would do the filleting part. Note your shape curve for the extrusion is not planar - I would make sure all curves are planar if they are mean to be and tangent if they are meant to be. The key in making the fillets is to split the edge at the point where you want zero radius and add a handle where you want the radius to begin tapering.

strap2_PG.3dm (634.7 KB)


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Hi Pascal, I got a better understanding on Fillet Edges after looking at your file. Many thanks!

Using Cap command is definitely better. Many thanks!