Self-Intersecting Curve.

[a1harps]

When I try to extrude this closed polyline (yes it is closed) I get the message "Cannot sweep or extrude a self-intersecting curve." I do this sort of extrusion all the time (closed polylines with various geometry) and usually have no trouble.

 

Can anyone shed some light as to why this is happening?

[ReMark]

Sounds like you have some suspect geometry in your profile. Either redo the geometry or explode what you have and find the errant piece(s) and correct the situation.

[a1harps]

Thats why I posted in...I spent a lot of time painstakingly checking every intersection to make sure there were no overlaps or shortfalls. I don't understand why "pedit" will close the polyline if there is a problem with the geometry?

 

Usually when in "pedit" and you close bad geometry a line will form where you don't want one. In this case the closed polyline is the shape I need.

[ReMark]

I agree. That's what you and I would tend to think. AutoCAD, as it has demonstrated, thinks otherwise. What can I say? You don't have to convince me you have to convince AutoCAD. Draw it again.

 

Maybe there's a stray bit of line somewhere?

[Crazy J]

I can't see too closely, but is the object simply the four arcs and some straight line segments? If so, could you just try to draw a new pline, picking the same osnap points as you go? I would suppose that would work. It might not give you the root cause of your problem right away, but perhaps in the process you will figure something out about the cause... and it should get you going on what you are working on now.

 

But then sometimes, if I know I worked around a bug but can't find what that bug actually was, it bothers me even more....

[Crazy J]

Also, would this be a case where PRESSPULL could work? Don't have that command in my version, but I see a lot of uses for it in other posts. Just a thought.

[eldon]

The only way for someone else to have a check is if you can post the drawing. My eyes are not good enough to see on your screen shot.

[ReMark]

Not sure if the following may apply to your situation but someone inquired over at the AutoDesk Discussion Groups about overlapping polylines on the same plane causing problems. Bill Gilliss responded with a lisp routine that identifies the overlaps, creates regions, and zooms to the offending area in the drawing (pretty freakin' amazing if you ask me). He posted version 1.01 of his routine in the last post of the thread. The routine is named polylineoverlap.lsp in case you are interested.

 

http://discussion.autodesk.com/forums/thread.jspa?messageID=6346499

[Glen Smith]

I've had good luck using either BOUNDARY or REGION when AutoCAD and I differ on what a shape actually is.

 

Glen

[alanjt]

I've had good luck using either BOUNDARY or REGION when AutoCAD and I differ on what a shape actually is.

 

Glen

 

Type BPoly and pick a point inside of the object.

[JD Mather]

Explode. presspull, done.

 

Oops, you are using 2004 - you will have to find the problem or attach the file here for someone else to find the problem.

[Hoozin]

Assuming that it's two points sitting on top of one another (the most likely culprit), you can find it using PEDIT > Edit vertex > Keep hitting Next til you get to a vertex where the X doesn't move.

 

This is pretty void if it will form a region though. Just REGION, select the PLine, extrude the resulting region.

[alanjt]

If you can't get it to BPoly witin the PLine, there is another option...

[a1harps]

Lots of great info!

 

Sorry JD...my profile is dated..I am on V2007.

 

I tried the lisp but it told me the same thing..cant extrude self intersecting curve.

 

Anyway I redrew the whole...changed to poly....same result.

 

I then exploded ....closed and opened a few of the separate curved elements....rejoined and for some reason autocad now sees it as extrudable so I am back to work.

 

Thanks for all the good info.

[a1harps]

@ Alanjt....your method of answering questions is great with the mini movie!

 

Is there any way you can slow it down a bit?...I can't read the commands fast enough.

[alanjt]

@ Alanjt....your method of answering questions is great with the mini movie!

 

Is there any way you can slow it down a bit?...I can't read the commands fast enough.

Rectangle>BPoly

[SuperCAD]

Here's another vote for PRESSPULL. You'll learn to love that command, especially with shapes made with splines.

[MikeScott]

when you changed the arc direction during the creation of the pline.. the last pixel of the arc might have been 90-degrees, which might have matched the lead pixel of the next arc, or was so close it was being "rounded off" that way. Or you would cross that 90-degree point if you are even .00001 below the quad position on the arc.

 

That would have created the overlap area AutoCAD was whining about.. Always remember that you're dealing with points that are absolute points, something along the lines of .00001 accuracy internally.. regardless of how you've set your CAD settings. When you do arcs from a point, you need a degree or so between the two arcs or ACAD might decide to round it off.

 

I hit that problem when extruding molding profiles. Now I make "reasonable" arc intersections that can be cut by a real blade, rather than running to zero, on neighboring arcs that are so far from continuing the arc I used to get there.

 

The other option might be to do it in two-three pieces and union them together.

[MikeC1956]

in fact, I just got this error, I used select to find the number of entities (a symmetrical part) and the selection had an odd number of lines. I began a somewhat tedious search for the culprit(s). Sure enough, when I closed the polyline it gave the geometry an extra line. With no way of telling what the issue was, prior to the tedious search. I exploded the pline, deleted the malefic beastie, reran the pedit command, joined all segments, closed the pline then extruded the geometry w/o further incident.