Welcome to the Onshape forum! Ask questions and join in the discussions about everything Onshape.

First time visiting? Here are some places to start:
  1. Looking for a certain topic? Check out the categories filter or use Search (upper right).
  2. Need support? Ask a question to our Community Support category.
  3. Please submit support tickets for bugs but you can request improvements in the Product Feedback category.
  4. Be respectful, on topic and if you see a problem, Flag it.

If you would like to contact our Community Manager personally, feel free to send a private message or an email.

Stange behevior of loft

MathMath Member Posts: 8

I am currently designing a scoop, using a loft.
The loft is define by :
  • A conic (semi eclipse) on a plane parallel to the Right Plane with an offset
  • A semi circle on the top plane
  • A Guide using a line design on the font plane between the semi eclipse and the semi circle
And the result is stange, I obtain a dissymmetry on the loft :

The semi-circle and the semi-eclipse are strictly symetrical compared to the front plane. So I don't understand why I have this dissymmetry on the loft. An when I create the loft, if I reverse the selection order of profiles of the loft, the dissymmetry change of side.

I make a test, designing the exact same loft (same profiles, same guide) but alone (without the first main sketch and the first two extrusion I have in my current desing) and I I obtain a perfect loft without this strange dissymetry.

So I really don't understant  what appen in my design that can conduct to this dissymmetry ?

Thanks !



  • owen_sparksowen_sparks Member, Developers Posts: 2,660 PRO
    Hi Math and welcome. It's easier for people to help if you provide a link to your document. I'm sure someone will jump in and help then. Owen S.
    Business Systems and Configuration Controller
    HWM-Water Ltd
  • owen_sparksowen_sparks Member, Developers Posts: 2,660 PRO
    Hi again.
    I was able to get it to work by moving your profile sketch onto a new plane with a zero offset from the face it was on.  In theory this does nothing but actually it stops Onshape automatically using geometry imprinted on that face.  I'm not 100% sure that was what was going on here but it works  :*

    Link here

    Owen S.
    Business Systems and Configuration Controller
    HWM-Water Ltd
  • MathMath Member Posts: 8

    Thanks, It works like this ! But I really don't understant the Onshape Behavior for this case and the need of a new plane !

  • lanalana Onshape Employees Posts: 532
    I think we can improve that behavior. I grabbed an issue on it. 
  • MathMath Member Posts: 8

    Thanks for you answer lana.

    I'am here again because there is an other behavior of my loft that I don't understant again.

    Waiting the answer oven_sparks, to get around the problem I mention before, I had add guide for my loft (Using 3D fit splines) :

    So I carry on my design of scoop. And at the finishing of my design and make a smooth leading edge of my scoop, I use the Fillet function (see previous picture).

    After, I make a second part studio I restart the design of the scoop using the tips given by owen-sparks. As I said before, I works for the loft.
    But when I try to finishing my scoop with a smooth leading edge (like the previous one), the fillet function doesn't works ! And I don't understand why because event if the method to build the scoop is different, the result is the same. But the Fillet function doesn't work !

    So, any idea what appens now ?

    Thank a lot !

Sign In or Register to comment.