Hi. Having an issue with Boolean difference. Does not seem to work.
Where am I going wrong? Tried several other means to separate object using other commands. Still to no avail.
Received "Calculation Failed" error message in dialog.

Tried this in ver3 and ver4



The attached 3dm.

Maybe because you helixoïd volume is auto intersected!

Kill the 2 cover plates
Make a Trim = you will obtain some curious result with some double skins...as if volumes are copy cat from the origin...

If you give a thickness (make a sweep with 2 concentric circles) that quasi works! :)

Hi 3d2cnc, yes it's like Pilou writes above - you don't have a well formed solid there because the surface crosses over itself. A self intersection in the "skin" of a solid will tend to cause volume oriented calculations like booleans to fail.

How did you create the spiral part, can you post the curves used to construct it? Something like making it in 2 pieces that then get booleaned together may do the trick. Also if using sweep it would probably be good to use the "Twist : Flat" option so the seam edge would be in one location rather than twisting around.

- Michael

Thank-you Pilou.

I have read many of your posts and have visited your Site many times.

Followed many of your links.

Very informative... and your compilation of documentation is robust.

I was wondering just why this cross-sectioning was not working with Boolean Difference.

Looking forward to reading more from your contributing work.

As soon as the first volume is not auto-intersected all works as supposed to be! ;)



Maybe can you try in other progs (freeCad... Fusion 360...)for see if you obtain the same result...

Thank-you Michael.

MOI is amazing. Inspirational. Intuitive and easy to use. The first thing that caught my eye towards using this great Software was how simple it was to swap and design through split views. It is becoming easier to navigate.

You have answered my question;

(self intersecting solids, the "skin" of a solid will tend to cause volume oriented calculations like booleans to fail)

Is there a way to skin such an object or cover just the outside of the object, lending a way to achieve the cross-section?

Script perhaps?

Thank-you
Dave

Maybe try with two donuts which overlab a little, rather than helix?
- Brian

Hi Dave,

re:
> Is there a way to skin such an object or cover just the outside of the object, lending
> a way to achieve the cross-section?

That would be pretty difficult. Probably the easiest way to get a good solid for your case here is to build it out of 2 halves so that each piece only intersects the other and not itself. Then they can be combined with boolean union.

Here's what that looks like, also see attached 3DM file where the boolean difference should work now:







- Michael

Super tricky! Bravo!

That method works.

Selection of profile is important.

Self intersecting Bad.

Thank-you.
Dave