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GemmaEBaird

'Cannot sweep or extrude a self-intersecting curve'

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GemmaEBaird

Hi

 

 

I keep getting the above error - but the curve does not intersect itself - is on the same plane and does not intersect another curve.

 

 

I've tried to re draw a few times but I still get the same error.

 

 

Any ideas ?

Curve.jpg

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nestly

I ran into that same error with your previous drawings when trying turn the profile into a closed polyline to EXTRUDE. I didn't take the time to identify exactly where the geometry overlapped. You may try using BOUNDARY command (BPOLY) Which will create a new closed polyline boundary on top of the existing geometry, then delete the previous objects.

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GemmaEBaird

That doesn't seem to work - an I appear to be making the same mistake over and over - it's very frustrating.

 

 

I've attached a sample drawing. I'm trying to extract the yellow curve from the blue form

Curve Test.dwg

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nestly

I'm actually not getting a error extruding the yellow curve in the attached drawing. Are you trying to get the intersection of the blue solid and the yellow curve after it's extruded?

 

Extrude.gif

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GemmaEBaird

I am, but I can't even extrude it to do that ?

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nestly

I guess I was mistaken the first time. I must have run BPOLY prior to making the previous animation.

Polylines can only be created on the current UCS, therefore you must reorient the UCS before using BOUNDARY command (BPOLY). I switched to "LEFT" UCS in the demo below, but you can use whatever method you prefer (ie UCS > OBJECT etc) The new polyline that BPOLY creates should not have the self-intersecting problem. Hopefully you can figure out what's happening in your workflow to cause the self-intersecting curves.

 

BOUNDARY - BPOLY.gif

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GemmaEBaird

I'm doing exactly what your doing ( the video is INCREDIBLY helpful - thank you ) but I'm still coming up with an error ??

BPoly.jpg

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GemmaEBaird

OK - I've SORT OF fixed it.

 

 

I've rotated my model around so that the face is on a 'world' UCS if that makes sense. Its a bit of a pain and once I come out of 'left' 'isolated' view my poly is somewhere random. But as I said - it sort of works.

 

 

I've got about 40 of these to do with different curves so carrying on like tis is going to be a little elongated

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nestly

The error in your screencap is because although you're viewing the polyline from the "side", Autocad is still using the WCS (World Coordinate System) so it's seeing the object from the "top" so it's only seeing the object as a "line" not an open profile.

 

A key to working in 3D is being able to understand and manipulate the UCS. As you've discovered, it's inefficient to move/rotate objects to match the WCS, so instead move/rotate the UCS to match the object. A sure fire way to make sure the UCS is aligned with the object is by using UCS > Object (notice how the direction of the crosshairs change in the animation below after using UCS > Object, clearly indicating the X,Y,Z axis'

 

UCS-Object.gif

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GemmaEBaird

Thank you - yes I understand that.

 

 

It still seems to be a little hit and miss though - but better

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