AutoCAd 2008 3D

[Nellie]

Hi Guys and girls I've been using AutoCAD 2008 for 3D modelling for a while now and find that it (CAD) can become unpredictable in drawing terms.

If i want to extrude a rectangle it will but if I put a small radius on the same rectangle it gives "Modeling Operation Error: Segment chord not perpendicular to normal. Unable to extrude the selected object" it will give the same error each time i redraw the same rectangle and will then work.

It seems to me that AutoCAD 2008 does funny things for no reason (above is only one example), Is this just my CAD? I have the latest patched from the Autodesk website.

Can someone recommend a better 3D package before I pull out what's left of my hair?

Thanks in advance.

Mr Stressed.

[ReMark]

I could not find a reasonable explanation for the problem you are experiencing at the AutoDesk website. A vague reference to it was found at the AUGI website. In the midst of another thread someone reported getting the same error message. The responder's only observation was that it appearred the user's drawing had objects located an extreme distance from the origin of 0,0,0. Why that would affect anything I cannot say.

 

You say it doesn't work initially but eventually does when the rectangle is redrawn. What are you doing differently? How is the rectangle drawn in the first place? What is the radius that you are working with? How is the corner of the rectangle radiused in the first place (what method do you use)?

[shift1313]

the only reasons this may not work are if your line segment ends do not form a closed polyline. Even if it looks closed and you zoom in it may not be.

 

Next would be if any of your endpoints have a z coordinate. Everything needs to be in the same xy plane.

 

how are you putting the radius in? are you doing this to all corners? is it a closed polyline before you begin? what if you fillet after the rectangle as been extruded?

[Nellie]

Thanks for the quick replys guys.

 

All i'm drawing is a simple rectangle using rec, D, width then height so its draw by CAD and should be closed, I then used F, R at 150mm.

 

I could extrude the rectangle but as soon as i used fillet it gave me the error. but seems to work after redrawing it 5 -10 times. very strange.

 

It's not the first time my CAD has done funny things like that.

 

What 3D package do you guys use? I'm thinking of getting MEP. have you used that and what do you think of it?

 

Thanks again.

 

Alot less, Mr Stressed

[Morgan]

try joining everything back together after filleting.

[Nellie]

I have tried exploding and using pedit but it would not turn back into a polyline.

 

Cheers

[Patrick Hughes]

I have tried exploding and using pedit but it would not turn back into a polyline.

 

 

Therein lies your problem. There has to be a reason it is not allowing you to join. Most likely is that sometime between drawing the rectangle and performing the fillet your coordinate system is changing.

 

Another option is to fillet the solid after doing the extrusion.

[Nellie]

You might be right but why would it work right after redrawing a few times?

 

I have no idea you could fillet an extruded object.

 

Thanks

[ReMark]

I'm working in AutoCAD 2009.

 

Yes, a solid can be filleted.

[Patrick Hughes]

If I remember correctly the rectangle command constructs a polyline rectangle and it used to be a lisp command.

 

I'm not a big fan of polylines so I rarely construct things as polylines. Rather, if I don't costruct solids from primitives then I construct geometry from elementary entities and then join into polylines for extrusion or revolving etc.

 

I think there are times when you fillet a polyline that AutoCAD generates the fillet with a random extrusion direction based on the polylines that are being filleted. I could be all wet on this though. You could examine the radius after doing an explode with the list command and see what value it has for the extrusion vector.

 

As for filleting a solid, yep. Sometimes it's even quicker and more handy as you only have to pick an edge as opposed to 2 lines.

[Nellie]

Thanks for the advice guys.

[shift1313]

i use autocad for most of my solid modeling. That and inventor. I do use other software packages though but autocad can do most of it all(if not all).

 

when you perform the fillet command on your rectangle, how do you do this?

 

when i do this on a closed polyline i just type fillet. R for radius, then select the object(will select it all but where you pick is important) and then other side of the edge i wish to fillet.

 

This will keep the object "closed" and allow you to extrude it. If you select P for poly line in the instance of your rectangle, all corners will be filleted in the process, but it should still remain a closed polyline after the fillet. When you get this error and you select your object, does the entire thing become selected? What if you do PEDIT, Close and try to extrude?

[Nellie]

I was doing it the same way but i think CAD may have had a funny moment. the object was closed but still had to redraw it a few times.

[mugshot]

try fillet and then "chain"