Hi Tom, also what radius value are you hoping to use there? It appears that some larger values do end up working with your existing geometry, like for example radius = 0.5 seems to work ok over here (there is one edge missing in your yellow edges, make sure it's also selected before doing the fillet).

To get the fillets to perform better would probably involve smoothing out that creased edge which will probably involve some trimming and blending work, let me know if you want me to do that.

- Michael

Hi and thanks for the quick reply. I appreciate your explanations as understanding the reasons
behind the problems helps me avoiding them in similar situations.

No patch tp patch was involved here - I rotated a curve and cut out a chunk with boolean op.

"either side of that edge are not quite smooth to each other"

Possible that the initial curve I used was nor perfectly smooth . I attached it below.

"Hi Tom, also what radius value are you hoping to use there?"

I wanted to try out fillets of different radius and then choose one if them

Hi Tom,

> Possible that the initial curve I used was nor perfectly smooth . I attached it below.

Yeah, that's probably what happened there. The end direction of a curve is controlled by the direction of the last 2 control points, so for example if you extend out a line through these 2 points here you can see that it is slightly off of the neighboring line:






Anyway that's about the type of shallow sharpness that will make things difficult for filleting.


> I wanted to try out fillets of different radius and then choose one if them

Do radius values of 0.5 , 0.6, 0.65, 0.75, work ok for you over there? Are any of those adequate?

- Michael

>>Yeah, that's probably what happened there.<<

Ill redo the curve and repeat the process - then filleting should work.>>Do radius values of 0.5 , 0.6, 0.65, 0.75, work ok for you over there? Are any of those adequate?<<

Ill give it a try now

Sorry to report that it did not work yet. Attaching the last file

Hi Tom, I loaded your last posted file and radius values between 0.55 to 0.9 seem to be working well with it now.

Will anything in that range do for what you're looking for or are you trying for a smaller value than that? I don't know at the moment why the smaller values aren't working, but I can investigate some more if you want.

After a quick look, it might be the same kind of problem on the other cutting direction, looks like slight creasing here:



- Michael

Hi Tom, yeah it's pretty much the exact same thing on the profile on your cutting object:





If you tune up that curve so it's fully smooth with the lower line, and then make a new cutting block out of that, I'd think that should fully clean things up. A quick way to put in a smooth curve between 2 lines is to select the lines and then run Construct > Blend.

At some point I may modify the Edit > Join command to look for things that are nearly tangent and automatically adjust them to be fully smooth with one another but it's a bit of a delicate thing to do always because in some cases it can kind of change the shape too.

- Michael

Hi Tom, I've attached a tuned up version here - I did an "untrim" on your main body to restore it to its original full shape, then deleted the slightly off round corner in the above screenshot and put in a curve blend in there instead and then extruded a new cutting block from that, then did the boolean.

With this attached version you should now have "all systems go" for doing any fillet radius along that spot.

That particular type of thing with things being only just a 5 degrees or so off from smooth tends to make filleting pretty cranky.

- Michael

Thank you for the patience, your informations are really helpful. Impossible to come up with
a solution without it. Will have a look at the file - great !

Everything fine now after reworking the curves.

Dealing with filleting I realized that it is not possible to round with a perfect circle - for example if
you have a distance of 2,00 it is not possible to fillet with radius 1,00 exactly but a bit smaller than
the radius needed for a perfect circle.

Is there a specific reason behind it ?

Hi Tom, the fillet will fail if it would cause a face to be entirely consumed away as would happen in that case. The fillet engine does not currently know how to handle that type of case.

- Michael

Ok good to know, I had speculated that I may have made a modelling mistake.