This is 3dm: http://we.tl/nNsgUdKS0j

Hi Andrei, your cutting object is self-intersecting, basically you've got opposite sides of the shape here overlapping and touching each other:




That tends to make for a poorly defined volume, especially if the surfaces actually wiggle through each other slightly.

Then also having that same area trying to overlap on the base object being cut makes for a highly complex type of surface/surface intersection.

You will probably not want to have such a very thin wedge type shape in the cutting object and it will be better for the boolean if you can make a cutting object that pushes some amount through the object to be cut rather than having a "barely skimming" relation with surfaces that overlap over very similar surface area. It can be ok to have overlapping sometimes if the surfaces are very precisely duplicated in the overlap area, but if one of them comes from some fitting operation and just barely waves in and out of the other that makes for a very difficult and complex intersection.


You can instead use Trimming to do a more targeted type of cutting to get the final result, rather than doing a boolean which is based on volumes.

Delete the outer face of your cutting object, then select the main object and run Edit > Trim, then for the cutting objects select the naked edges of your cutting object. That will then trim the surface and you can discard the piece you don't want, and join the results back together which is how I got the attached result.

- Michael

Michael, In my video, I can boolean when there is no fillet, but after filleting I can not, these intersecting surface apear after fillet? Loks a bit strange. And in my video I trying to trim this surface and it gives me hole in the end of the video. What I made wrong?

I tream a bit diffrent way.. and get that hole hm.. What is the case?

I made mutal trim in my video... And it does not work as good as select cuting objects when trim.

Hi Andrei,

> I tream a bit diffrent way.. and get that hole hm.. What is the case?

If you are trying to trim with the entire object as the cutting object, MoI will likely be trying to do some surface/surface intersections as part of the cutting operation, and like I was mentioning before in this kind of situation with "barely skimming" surfaces you don't want to do surface/surface intersections.

So instead select edge curves as the cutting object, rather than selecting the full object as the cutter. That should avoid any surface/surface intersections from being done at all.

That's how I did that previously attached file - for the cutting objects I selected all the naked edges (by using the select naked edges script), not the entire object and not both objects as a "mutual trim" either.

- Michael

Another way you can see if there are intersection problems is to select the objects you're trying to boolean and do a Construct > Curve > Isect , which generates all the intersection curves between 2 objects.

If you do that in this case here, you'll see that because the surfaces just very slightly wiggle through each other there are complex intersections in those shallowly intersecting areas:




It's then very difficult for proper final trim boundaries to be created from this type of messy intersection results.

- Michael

Here's a way to get past it:

Michael, thank you! I understand, Idea with intersect is GREAT! Now everything is clear for me. Also Idea to select all edges in this case using naked esge script also is great!
BurrMan, good soltion too! Thanx)