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Stange behevior of loft

MathMath Member Posts: 7
Hello,

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 !

Math

Answers

  • owen_sparksowen_sparks Member, Developers Posts: 2,157 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.
    Production Engineer
    HWM-Water Ltd
  • owen_sparksowen_sparks Member, Developers Posts: 2,157 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



    Cheers,
    Owen S.
    Production Engineer
    HWM-Water Ltd
  • MathMath Member Posts: 7
    Hello,

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

    Math
  • lanalana Onshape Employees Posts: 448
    I think we can improve that behavior. I grabbed an issue on it. 
  • MathMath Member Posts: 7
    Hello

    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 !

    Math
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