round-to-square

[driftingsun3]

In my ductwork that I am attempting to render in 3d (in AutoCAD 2008), I have a square-to-round transition (a 14x14 square duct transitioning into an 18"diameter round duct). Does anybody know how to represent that in 3d? Lofting works for the four sides that each end at a point on the curve of the end of the round duct, but I don't know how to slap a surface on the other sides, because the surface is curved on the one end, and ending at a point on the other (not the best explanation, but anybody that works with sheetmetal or designs ductwork should be able to picture what I am after).

[driftingsun3]

In my ductwork that I am attempting to render in 3d (in AutoCAD 2008), I have a square-to-round transition (a 14x14 square duct transitioning into an 18"diameter round duct). Does anybody know how to represent that in 3d? Lofting works for the four sides that each end at a point on the curve of the end of the round duct, but I don't know how to slap a surface on the other sides, because the surface is curved on the one end, and ending at a point on the other (not the best explanation, but anybody that works with sheetmetal or designs ductwork should be able to picture what I am after).

 

I am using AutoCAD 2008 for this, I don't know how the smiley face got in there.

[nocturne00]

How do you mean present it in 3D? like a shop drawing for onsite an work?

and perhaps a screenshot could shed light on what your after

[driftingsun3]

Here is a link to the screenshot of what I am trying to draw; I am mainly just experimenting with drawing ductwork in 3d for my own personal education and practice (at the MEP firm that I work at, we only do 2d, with some "fake 3d", isometric riser diagrams and such). Anyway, you can see the portion of the duct transition that I have not been able to create a surface for, I tried drawing an arc on the end of the round duct and tried sweeping it; that didn't really work out. I also thought edgesurf might do something, but apparently that function wants 4 edges to work with. Any ideas would be appreciated. Thank you.

 

 

http://picasaweb.google.com/ebalong/CADScreenshots#5256480900799915634

[shift1313]

with acad 04 you are going to be a little limited. acad 08 gives you a few more options. Now you can use the loft command which will let you pick several cross sections. This would allow you to make one large duct run through several cross sections. The issue, if you used closed polylines you will get a solid. You should be able to either copy and scale down another one to subtract, or use the shell command, but the shell command wasnt working well for me.

 

If you want to use edgesurf you are going to need 4 defining curves. What i did was drew a RECTANGLE 14x14, exploded it, drew a circle dia 18, then created 4 arcs from this circle at its 4 quadrants. Alignment is very important. I had to rotate these ars 45degrees to line them up with the rectangle properly. draw lines from your arc end points to the line endpoints. That should give you the defining curves for edgesurf(which you can do in 04 or 08 the same).

 

One thing to note is surftab1 and surftab2.

 

Look at this drawing i just did

 

 

 

 

The two grey panels were done using what i just described with EDGESURF and SURFTAB1 was set to 6 and SURFTAB2 was set to 6. The two blue panels were dont the same way but SURFTAB1 and 2 were set to 15. You can see you will get much better resolution that way.

 

Since you are using 08, loft will make the entire duct run much easier and give you more control over the final shape with a lot less effort, and thats how i would recommend doing it.

[driftingsun3]

Thanks, that should give me what I am looking for (or something close); I'll try some of the other techniques from previous posts (I should have done a search on this topic before posting a new thread, it seems like a lot of people have run into this before, sorry).

[tzframpton]

In my ductwork that I am attempting to render in 3d (in AutoCAD 2008), I have a square-to-round transition (a 14x14 square duct transitioning into an 18"diameter round duct). Does anybody know how to represent that in 3d? Lofting works for the four sides that each end at a point on the curve of the end of the round duct, but I don't know how to slap a surface on the other sides, because the surface is curved on the one end, and ending at a point on the other (not the best explanation, but anybody that works with sheetmetal or designs ductwork should be able to picture what I am after).

You do realize there are ductwork packages of CAD programs out there so you that are full 3D Applications, correct? Didn't know if you are doing this just out of fun, or if you run 3D ductwork all the time.

[driftingsun3]

I'm primarily doing it for fun, but now that you mentioned it, are you referring to stuff like AutoCAD MEP, or add-ons to regular AutoCAD, or different stand-alone software entirely?

[tzframpton]

yes, MEP is one app. also CadDuct is another app, but that ties right into CNC machines for product output I believe.