Truncate a cone

[rijackson]

I have a cone drawn as a 3D surface, and I want to truncate the top of the cone at a 45 degree angle. Having read some posts on this forum and the AutoCAD help I am coming to the conclusion that it's not possible (I think I need to use a solid cone). Could someone confirm this (or otherwise) so that I don't spend any more time on it.

I'm using AutoCAD 2002. I have a total of 1 weeks experience so any answer should assume gross ignorance

Thanks
Richard

[Pocket]

First off theres a big difference in surfaces and solids

Imagine surfaces as pieces of paper bent around how the shape forms
Once you make a surface you are pretty much stuck with it as far as modifying it goes

Solids on the other hand have a definate volume and can be modified quite a bit

If you need to make a cone thats truncated at the top, Id draw a center line, then a line representing the outside edge of the cone and the trunkated part meeting at the top of the cetnerline
These are all 2D commands
Now to make this a surface you should either individually revolve them or change them to a pline and revolve them as one piece

Modify the smoothness by boosting the SURFTAB1 and SURFTAB2 commands. I usually do 24 for both

Now to make a solid cone Id do the same 2D as above, but close the figure with a line on the bottom
Now either region(my prefered method) or change the lines to a pline and close it
Next do a solid revolution about the center axis

Smoothness for this is controlled by ISOLINES
Default is 4, I usually use 8 or 12

I can post screen shots if your still having difficulty

[New2CADmike]

In your solids toolbar there is a command called ....cone...click it and autocad will ask for the center of the base,how wide the base is and then how tall will the cone be...after that slice the top off at a 45 at where you want it and you are done..is this what you are looking how to do???

[rijackson]

Thanks for the information. the analogy to a piece of paper is very helpful.

Unless I misunderstand something (which is quite possible!), won't your method produce a cone that is truncated perpendicular to the axis of the cone? I need it truncated at 45 degrees.

Richard

[rijackson]

In your solids toolbar there is a command called ....cone...click it and autocad will ask for the center of the base,how wide the base is and then how tall will the cone be...after that slice the top off at a 45 at where you want it and you are done..is this what you are looking how to do???

Yes, this is exactly what I want. Thanks. I was using a surface only because it's what I found first. I can see that I will have to start using solids, which are much more versatile.

Richard

[New2CADmike]

I can see that I will have to start using solids, which are much more versatile.

Richard

Yes very true...Get good with solids and you can create just about anything

Now what would be nice is to see if you can do it..in other words..show your work..lets see if you got the concept...

[rijackson]

Yes very true...Get good with solids and you can create just about anything

Now what would be nice is to see if you can do it..in other words..show your work..lets see if you got the concept...

OK. I can't post the full drawing, but here's one with almost everything deleted. I'll make it look nicer when I figure out how

Richard

[New2CADmike]

Good work!! I can tell that you have the talent..you just need to develop it..Keep going and don't be afraid to ask questions...