CAD Forum

I want to extend this surface but one surface is going in opposite direction. What is the reason? & How to fix it?

Not sure why the Extend Surface is doing this, could you upload the file?

One solution would be to skip that middle edge, then use Fill Surface applying tangency in the three edges

This was an issue with a part in reddit website. I resolved this with different method after realizing that Extended Surface is not responding favorably. But I want to know only why Extended Surface behave like this.

You can only rely on Extend Surface to do something predictable with analytical (simple) surfaces, or for short distances. Plus, it looks like you are trying to extend several surfaces at the same time. Complex spline-based surfaces can't be reliably extended because a spline is not predictable like an arc or a straight line. You can't expect extend to work in this situation.

Thanks

@matt is the curvature comb from splines the reason for this odd behaviour?

You should definitely take a look at the Spanner SolidWorks Webcast if you do more of this stuff, @Maha Nadarasa.
He also talks about avoiding surfacing at all costs!

berg_lauritz wrote: ↑Thu Aug 05, 2021 10:22 am @matt is the curvature comb from splines the reason for this odd behaviour?

Yes and no. Yes because if the curvature is tight at the end where it is extended, it's going to be just a tight (and probably self-intersecting) loop.

And no because how do you extrapolate a non-periodic function? You can make it straight-line tangent (which is one of the options, but still won't work because there are multiple surfaces), you could continue the curvature, or continue the curvature trend. Both will eventually intersect themselves.

Extension works sometimes. I would try Untrim first, and if that doesn't work, try Extend, then if that doesn't work, just build the surface that you want.

@ berg_lauritz

berg_lauritz wrote: ↑Thu Aug 05, 2021 10:22 am You should definitely take a look at the Spanner SolidWorks Webcast if you do more of this stuff, @Maha Nadarasa.
He also talks about avoiding surfacing at all costs!

Thanks for the information

Maha Nadarasa wrote: ↑Thu Aug 05, 2021 5:58 am This was an issue with a part in reddit website. I resolved this with different method after realizing that Extended Surface is not responding favorably. But I want to know only why Extended Surface behave like this.

Hmmm, I can use Extend Surface in this file without problem. ._.?!
Extension Type: "Same surface" instead of "Linear"

@Lucas

Thanks for the valuable information

Sure, glad to help