iges model distorted after imported to Solidworks

Hi,
I am facing a problem when importing a curve iges surface. It seems to
me the curve surface is actually distorted after import to Solidworks.

The surface consists of entity:
128 - nurbs surface
126 - nurbs curve
102 - composite curve
142 - curve on parametric surface
144 - trimmed surface

I then saved it as another iges file by using Solidworks then compared
the original iges file with the new one.

I found that the control points at type 128 and 126 are same bt. the 2
files. However the knot vector and weight are slightly different.

I tried different setting and the result remain the same ie
solid : case 1. try form solid
case 2: knit surface
case 3: do not knit

I wonder if this is a common issue? Is there solution ?

I wonder appreciate if someone can give me some advice here.

Thank you.

jeff

 

Have you tried import diagnostics? I know when I get iges files
sometimes, they have gaps or missing faces, and import dianostics ha
repaired them every time. With Iges files you will find that most of
the time, the native model is the one with the errors even though you
may not see them. I have been shown where you take a model that you
create, save it off as an iges, and bring it back in. In a particular
case, it all of a sudden had errors.

So I would try import diagnostics first off.

 

Check the degree in the original IGES file.
What's the max SW supports?

 

the orignal no. of degree for all the curves is 1. However after
imported to Solidworks, the number of degree has been incresed to 3.
This really confuse me.
There is only one curve surface that I import to. So this should be a
stright forward thing, simply read in the data as defined in the
original file.
However it seems to me the kernel has done additonal work.
Is this very common?
Please correct me if I am wrong.
thanks

jeff

 

This should only be true for straight lines between two points.
Have you read it correctly???