3D Elliptical Vessel Heads in AutoCAD

[dbakeg00]

Hello All,

 

I'm new to the 3D side of AutoCAD and I am looking for some help in drawing 2:1 elliptical heads for pressure vessels. I'm currently using AutoCAD 2010. Would anyone care to help walk me through it? Thanks in advance.

 

Regards,

db

[ReMark]

Well if you can draw the profile in 2D you're halfway there.

 

Will your tank be drawn with a shell thickness?

[dbakeg00]

I can draw the 2D and yes, it will be drawn with a wall thickness

[ReMark]

Example of an elliptical head drawn in 3D. Head thickness of 3/8".

 

Visual style: 2Dwireframe

 

[dbakeg00]

Can you teach me how to go from the 2d profile to that?

[Glen Smith]

Try the revolve command. Draw your profile in 2D (making sure it is a closed polyline when you are done), type revolve, select your profile, seelct your central axis, 360 degree revolution and you're done. Ports, valves, fittin's, tax, tittle and tags are of course extra.

 

Glen

[ReMark]

You only need one-half of the profile if you are going to use the REVOLVE command.

[dbakeg00]

So how do I get the ellipse to turn into a closed pline?

[Glen Smith]

Assuming that the wall thickness of your tank is uniform, draw one half of either the inner or outer profile. PEDIT that line into a single PLINE, then offset it by the thickness of your tank wall. Connect the two lines and PEDIT them into a closed PLINE.

 

If your wall thickness is non uniform, draw the inner profile, and the outer, then connect and close.

 

Glen

[dbakeg00]

Ok, that works. Thanks for all the help guys, I appreciate it very much!

[ReMark]

We'll be expecting either a check in the mail or for you to post an image of the tank as proof of enlightenment.

[dbakeg00]

Here ya go...

 

Thanks again for the help.

 

 

One more question...is there any way I can draw a 3D ellipse where I can REGION/EXTRUDE it (like I would a circle) and then take the MASSPROP to see the CG info?

[ReMark]

Hmmm...Is that a silver bullet? Are you really the Lone Ranger?

 

Region/extrude a 3D ellipse? I don't see why not. Why? Did you run into a problem?

[JD Mather]

Here ya go...

 

viewres = 2000

facteres = 10

regen

[dbakeg00]

Hmmm...Is that a silver bullet? Are you really the Lone Ranger?

 

Region/extrude a 3D ellipse? I don't see why not. Why? Did you run into a problem?

 

Yeah. I guess I'm not really sure how to extrude a 3D ellipse since I created it using the revolve command, whereas I draw two circles then region then subtract and then extrude to make the shell of the vessel.

 

Im not sure if thats clear or not.

 

-db

[ReMark]

As long as you're working with a closed profile you can extrude it along a "path" representing the centerline of the shell. You can also use the Sweep command.

[dbakeg00]

I draw the profile of my ellipse and then cut it in half. Then when i try the pedit commmand it says "No valid objects selected."

 

Here is a picture of what Im talking about.

[ReMark]

And you tried to use the Pedit command because ___________________ ?

 

Please fill in the blank in 25 words or less. My eyes are tired. Thanks.

 

You can take just what you have there (the portion of the ellipse) and, after drawing a circle representing your tank's O.D. (or whatever the ellipse is based on) either 1) Extrude it using the circle as it's "path" or 2) Sweep it using the circle as its sweep path. Either way it should work (you will be creating a surface not a solid). How do I know? I just did it myself in AutoCAD 2010. Now, stop reading and start doing. I have every confidence in you.

[dbakeg00]

I was under the impression that I was supposed to make the ellipse a pline before I extruded it. (19 WORDS!)

 

Thank you for your help, sorry I'm such as pain...just very new to this 3D side of AutoCAD.

 

Here is a pic of what I have done so far this morning.

 

thanks again!

-db

[ReMark]

I think you got that impression because a couple of us thought you were giving the elliptical head a "thickness" in which case the profile would have to be a continuous polyline. I hope that answers your question.

 

It appears you are making good practice. Can't wait to see the tank with all its nozzles, manway, lifting lugs, insulation ring and anything else you commonly have on your tanks.

 

Get busy. We eagerly await your next creation! LOL