Loft between an oval and another none even shape causing twist

kurt_conyngham

I am trying to loft between an oval and a shape with 2 flat sides and circular ends, 
seems simple but on some, not all, it twists the loft, the most right hand part of the oval doesn't loft to the most right hand part of the other shape, it lofts to maybe the upper left hand part and so the new part created by the loft isn't a nice gradual taper, it twists in the middle, see attached picture.
All shapes are perfectly horizontal and symmetrical, if possible the model is public, please see
thanks, 

SquidLord

After a little tinkering, I think the problem is with the original sketch. The circular ports are single line segments without breaks, whereas the ovals are multiple segment compositions. When Onshape tries to loft the points to match, it has no points of reference.

Easy solution:

https://cad.onshape.com/documents/575cd49fe4b0366acbd98dd2/w/c889973ba077c91a011f6409/e/c805af4d20fa1467b28bdf42

Split the circular ports into two segments along the vertical axis. You don't even need guide rails, the split alone simplifies the necessary and -- pop, you're done. Everything just works.

Topology; it's the debbil.

shanshan

bradley_sauln

What is the name of the document? If possible please also add the link here.

kurt_conyngham

bradley_sauln said:

What is the name of the document? If possible please also add the link here.

https://cad.onshape.com/documents/7259f40b4c14c22d6fc19dd6/w/3ac6eb1afcabdcfb9f35fb06/e/5573038757232f5848c87808

That should be it, its a bit of a mess at the moment as im struggling with a few things but these lofts twisting are a pain

thanks!

SquidLord

After a little tinkering, I think the problem is with the original sketch. The circular ports are single line segments without breaks, whereas the ovals are multiple segment compositions. When Onshape tries to loft the points to match, it has no points of reference.

Easy solution:

https://cad.onshape.com/documents/575cd49fe4b0366acbd98dd2/w/c889973ba077c91a011f6409/e/c805af4d20fa1467b28bdf42

Split the circular ports into two segments along the vertical axis. You don't even need guide rails, the split alone simplifies the necessary and -- pop, you're done. Everything just works.

Topology; it's the debbil.

shanshan

kurt_conyngham

2 slightly different solutions, the first one with the link, this works but slightly squidges the lofts at one side, im guessing because it lines up the points of the round shapes with one side of the oval shapes,
the lower solution using 4 points appears to have made a perfect loft.
I also learned why some of my 'remove' lofts don't work, I simply wasn't clicking on the subject that i wanted to remove the material from.

One thing thats happening now, it will let me make one of the lofts the the next one errors, if i close and open the workspace again, it works on the next one and so on.  Software issue?

Finally, is there anyway to unsplit the shape I have split so i can move the points round the corners like the video above?

thanks guys