Hi Armin,

Answer about Trim_Boolean_Diff.3dm:

Looking from the Right view,Snap a straight line from one
Quadrant along the y-axis a bit more than the shape diameter.

You will see they don't intersect,so the shape is not symmetrical.

Hi Armin - the Trim/Boolean type confusion there is related to your revolve not being a solid. It's got a teeny-tiny hole in it right at the end of the profile curve on the underside:



If you zoom in quite a bit on that "pole" zone of the underside, you can see there is a tiny hole there, which has a small edge around it:




It looks like probably your profile curve did not have endpoints aligned vertically, one was a bit off of the revolve axis, making that result. It can be good to draw those kinds of things with a snap on to the z axis line for the endpoints to make sure they line up, or you can also turn on control points and use Transform/Align to line them up vertically.

It still is normally possible to slice a non-solid with a curve, but having a tiny edge right through the area you want to cut will tend to cause problems. Also the behavior will be more predictable with solids, since the booleans are more oriented towards dicing pieces up and determining which pieces to keep based on volumes. When you don't have volumes it can still work but the behavior will be somewhat more like trim.

The ones that worked better for you seemed to have a better alignment and so got built with a cleaner solid shape without any micro edges.

- Michael

Hi Armin, I see from Paolo's comment what the difference is between your shapes..

I think probably the ones on the left you did the revolve axis with one point of it snapped on to the end of the profile, and then used "straight snap" for the second point to make a vertical revolve axis.

For the other ones, it looks like you did 2 endpoint snaps for the revolve axis, so it made a solid but at a slight angle (since the endpoints are not vertically aligned I think).

That's why there are different results there. To get rid of that you'll want to get those profile endpoints vertically aligned, once the shape is set up like that then there would not be a difference between snapping to one end and then using "straight snap" or whether using 2 end point snaps.

- Michael

Hi Michael, Paolo,

Thanks for shedding some light on my problems. Not sure how I got into those screwed up sketches, especially with the part I tried to chamfer.
Those curves are actually edges I copied from another part. And after further investigation, the corners are "sharp" there. But at least I know now what was wrong and I can fix it.

Thanks again.

Armin