Driving myself crazy trying to do this

See attached screenshot. I am trying to subtract the darker green object (a surface created with “Sweep 1 Rail”) from the lighter green solid (created by extruding a curve). Nothing I’ve tried works. I’ve attached the simplified file (these are part of a larger model) that includes the curves used to create these objects as well as each object on its own layer. I am sure this still comes back to my lack of fully grocking the difference between surfaces and solids.

FYI this is supposed to be a slot for a zip tie.

SIMPLE EXAMPLE.3dm (307.1 KB)

Thanks in advance!

Cheers,
Michael

Your dark green object has self-intersecting surfaces and on top of that they are right on the intersect line with the light green boxlike object. That’s a recipe for failure.

You need to remake the ellipse object so it doesn’t fold over on itself, then the Boolean operation will likely succeed… Your end radius on the ellipse is too tight to allow your profile to sweep around it without a self intersection.

–Mitch

Your dark green object is self-intersecting - at the places where it intersects the side wall of the lighter object. You should create that dark object in a different way. Perhaps you can have the 1 rail on the inside of the rounded square? Or you could create two curves (the outer ellipse-like curve and the inner ellipse-like curve) and extrude those.

Thanks guys. How can you tell that it is self-intersecting?

I ended up creating the dark object as you can see here:

It was still problematic and I ended up having to redraw the lighter green object for some reason.

So I’m set with this model but I would like to know how you can tell if an object is self intersecting.

Let’s see if I can avoid a double posting on this answer :grin:

I intersected the two objects (the standard first step to check boolean problems ) and saw that I got 4 closed curves, instead of the anticipated 2. I then zoomed way in on where one of those extra curves were and saw that very clearly.

I just highlighted the object and saw the folds immediately…

Thanks again.

So when I do an intersection, nothing happens. Is that the test?

Helvetosaur, I do see the overlaps when I zoom in. I hadn’t thought to look for that. Thanks.

Well, in your original geometry, when you intersect both objects, you should be getting 4 intersection curves. Do you not get that result?

Normally, the test after a boolean failure is to intersect and check where the curve(s) are open. The intersections should be closed ( except, of course, if you are booleaning open objects, but that is a special case ). In your case, they were closed but there were 4 of them while there should have been 2.

wim - Do you mean by doing Solid->Intersection? When I do that, select the two objects and hit return, nothing happens.

Ok, for grins I moved the dark green part out of the other part by about 1mm so the fold line was not right on the intersection with the light green part - and that worked.

This might explain the intermittent odd problems I’ve had - perhaps there were folds like this in those other parts. Something to keep an eye open for in the future.

No, if that is the same as on Windows, this will try to do a boolean intersection.
Try Curve > Curve from Objects > Intersection.
The command is Intersect.

Great, thanks! New trick for my bag. That works. The command is the same on mac.