Filleting edges destroys surface


When I fillet the edges of a closed polysurface, it destroys one of the surfaces. Does anyone know why this happens, and how to prevent it? Thanks!

troubleshoot.3dm (275.9 KB)

That might happen if the fillet radius is too large for the thickness of the part and can’t trim properly into the model. Generally, you’d still see a portion of the fillet surface though. I am not seeing what you described using a .25 to .05 radius fillet on your model here. What radius did you use and what edges were selected?

Hello - I’d set the file tolerance to .001 here then create the fillets. As Brian points out, these should be less than .5 units on each of the parallel sets of edges so as not to ‘consume’ the vertical edge completely - or, the radii of the two fillets, if you are doing both sets of edges, should add up to less then the thickness of the part - I’d say less by 10X tolerance.

Meantime, just fyi, at the big bend, the two halves of that radius are not tangent - I assume they are meant to be -

You may want to go back and clean up the curves that generated this shape.

troubleshoot_cleaner.3dm (177.3 KB)

@james.f.markel - simpler and cleanly filleted.


Thanks, but I used a .125" radius for the fillet, which is plenty small. I guess it’s still a mystery why the surface keeps disappearing. I’ll just try and work around it.

Did you try changing the unit tolerance in your file as Pascal suggested to .001? It was at .01 and the radius you used requires more precision versus what I used for values. I tested .125 just now on your .01 unit tolerance file and can reproduce the issue, thanks for that as the precision of the radius amount was the key. After changing the unit tolerance in Options>Document Properties>Units to .001 it works. You can also change the display precision so that the preview on the fillet handles reads .125 instead of .13.

Yuuuge number of spans does not help. Maybe use simple and easy degree 5 curves for your main surfaces. Bad quality surfaces are often behind many mundane issues.

Yes, that does the trick. Thanks Brian!

I will go ahead and clean up the curves. Thanks again Pascal!