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Topic ClosedElliptical Dome
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mmaurigi View Drop Down
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Joined: 21.Oct.2012
Location: United States
Using: AutoCAD 2009
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Points: 43 		Direct Link To This Post Topic: Elliptical Dome
    Posted: 04.Oct.2013 at 21:21
Can someone help me with how I can create a 3D model of an elliptical dome?
 
The ellipse dimensions are 14"wide x 18" long and the dome is 4" high. This would be the cover for an elliptical manway on a pressure vessel.
 
Like this:
 
Thank you.
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SEANT View Drop Down
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Joined: 09.Jan.2012
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Points: 31 		Direct Link To This Post Posted: 05.Oct.2013 at 11:57
Here is the elliptical shape you described.  It was produced by an plugin app that, unfortunately, is not available for AutoCAD 2009.uploads/244286/Ellipsoid.dwg
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John Connor View Drop Down
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Points: 7175 		Direct Link To This Post Posted: 05.Oct.2013 at 12:42
A dome like that can be constructed in 3D with a segment of an ellipse that is revolved.  Did you want to end up with a surface or a solid?


Edited by John Connor - 05.Oct.2013 at 22:20
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

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John Connor View Drop Down
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Points: 7175 		Direct Link To This Post Posted: 05.Oct.2013 at 22:17


This is how I did it.  By the way, it is a revolvedsurface.  You can union the four pieces together to form a regular surface then you can use the Thicken command to turn it into a solid.


Edited by John Connor - 05.Oct.2013 at 22:23
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

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mmaurigi View Drop Down
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Points: 43 		Direct Link To This Post Posted: 05.Oct.2013 at 22:59
Is that app available for 2013?
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John Connor View Drop Down
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Points: 7175 		Direct Link To This Post Posted: 05.Oct.2013 at 23:50
One.  I used AutoCAD 2013.

Two.  There is no "app".  All commands can be found in AutoCAD.
"Humans have a strength that cannot be measured. This is John Connor. If you are reading this, you are the resistance."

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SEANT View Drop Down
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Joined: 09.Jan.2012
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Points: 31 		Direct Link To This Post Posted: 06.Oct.2013 at 09:43
I don't think RevolveSurface can be used due to the squashed height of 4".  Loft can be used but creating an ellipsoid with tight tolerances (Mathematically correct surface area and volume) is difficult.
 
I think the "app" reference pertains to the one I alluded to in my post.  Unfortunately, The compatibility of the routine is only AutoCAD 2011 - 2012.  If needed, I'll try to update to 2013 - 2014, but it wouldn't be available until later this week.  In the mean time, this link has some discussion on the matter as well as hosting my current routine and a lisp variant by Marko Ribar.  See Reply 14.
 
 
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Kent Cooper View Drop Down
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Points: 683 		Direct Link To This Post Posted: 07.Oct.2013 at 14:51
Can you do it with a one-inch diameter hemispherical dome (quite simple to construct), defined as a Block and inserted with appropriate differing X, Y and Z scale factors?
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philippe JOSEPH View Drop Down
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Joined: 14.Mar.2011
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Using: AutoCAD Mechanical 2017
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Points: 1481 		Direct Link To This Post Posted: 07.Oct.2013 at 15:37
Yes Kent you can do it and it works.
I did a bloc 1x1x1 with a half sphere and scale it to X:14 , Y:18 , Z:8.
I did an other bloc at scale X:13 , Y:17 Z:7 to figure the volume to be taken out of the first one ( would be a volume of thickness 1" ) but I was not authorized to explode these blocks "non uniform scale".
The Ellipsoid.dwg provided by Seant is OK but I don't know if we are abble to generate with our AutoCAD.
Sometime I ask a colleague to generate on Solidworks "impossible" volumes for me, maybe we have ( or not ) that possibility.
maybe someone on the planet can help us...


Edited by philippe JOSEPH - 07.Oct.2013 at 15:53
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SEANT View Drop Down
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Points: 31 		Direct Link To This Post Posted: 08.Oct.2013 at 08:26

Phillippe, AutoCAD includes capabilities in its APIs that are not exposed to the drawing editor.  One of the capabilities allows for degree 2 NURBS surfaces.  I used that to sculpt the ellipsoid solid attached to post #2.

 

I see you are using AutoCAD Mechanical 2012.  That is the same version I used when running the plugin ellipsoid.dll attached to post # 14 of the theswamp.org link above.  I do understand, though, reluctance to run outside code. 

The source code for that routine can be inspected (and/or used to compile) here:

http://www.acadnetwork.com/index.php?topic=104.0

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