sweep

[ica_cici]

Hi All,

 

I need to make a twist oval solid, it made of two 2 wires D=1.20 and the dimension is 10.80 X 8.85 X 2.00. (see picture sweep)

 

So, I use the sweep command to make this solid. But after sweeping 2 circles object along an ellipse path I got a little bit different result than the real objects. (see picture sweep1) For information the twist angle I used is 3240.

 

Did I have a wrong procedure when sweeping the 2 circles?

 

Thanks for help.

sweep_.zip

[JD Mather]

I couldn't find your sweep path in the dwg file? When doing 3d you should always have delobj set to zero so that your originating geometry is preserved.

I always put this stuff on a hidden layer in case I need it later. In this case I cannot analyze where you went wrong without the profile and path. I have no motivation to create the geometry myself since I know you had it and did not attach it here.

[MikeScott]

In the real world, the wires deformed and flattened against the main shape wire. Autocad isn't going to do that.. it'll just faithfully create the shape you tell it to.

 

If your profile shapes were "preflattened" then the problem is that the sweeps didn't cause the profile to rotate on the spiral's axis (the main wire they're wrapped around).

[ica_cici]

Don't know much about Helix command Remark, does it for the path?

 

I'm sorry JD Mather, I forgot to write the information about the path, It's an ellipse size 8.80 X 6.85 and the profiles are 2 circles D=1.20. The target is an oval twist solid (10.80 X 8.85 X 2.00) and here's the history:

 

Command: sweep

Current wire frame density: ISOLINES=4

Select objects to sweep: 1 found

Select objects to sweep: 1 found, 2 total

Select objects to sweep:

Select sweep path or [Alignment/Base point/Scale/Twist]: t

Enter twist angle or allow banking for a non-planar sweep path [bank]: 3240

Select sweep path or [Alignment/Base point/Scale/Twist]:

 

No, the profiles was not preflattened, MikeScott. Its just 2 circles sweeps to a plain ellipse path.

 

Did I use a wrong path?

sweep_.zip

[JD Mather]

Don't know much about Helix command Remark, does it for the path?

 

Helix command is not going to help in any way as your path is not a helix.

 

I forgot to write the information about the path...

 

OK, I see what you are trying to do now. It is not going to work to twist around an ellipse. If you click on your solid you will see an elliptical "corkscrew" edge highlighted. Your desired path will actually be a curve similar to this. Somewhere I have an Excel spreadsheet formula to create the curve, but now I can't find it.

If someone can recall the technical name for a curve of this type perhaps that will jog my memory to find the *.xls

 

The key will be to get the correct math curve for the path at the center of your sweep profile with the profile perpendicular to the path at the start of the sweep.

[ica_cici]

So, it means that I have a wrong path, Is that right?.

 

Does it prevail to all circle profiles (single, triple, etc...) or it just prevails to double circles profile?

 

Why it's different if the profile is a square?

[MikeScott]

hmm.. I'd make preflattened circles and sweep those.. looking at the reallife picture, those things are flattened on the inside, permitting them to appear to "snug up" to each other more. (likely caused by the force exerted to twist them like that)

 

Also.. the circles should be tilted from the plane that the line is on. I can't see if you've done that or not, but otherwise the circles aren't "growing" correctly.. they're sliding as they turn, rather than properly extruding.

 

If you could section the realife one without disturbing it, you'd have two pieces of information tht could prove to be critical:

#1- the true profile

#2- the true angle of that profile in regards to the sweep path.

 

Another thought occured to me.. is there a wire that these two wires are wrapped around? It looks that way in parts of the supplied image.. that would mean there needs to be a distance between the profile and the sweep line.

[SEANT]

As mentioned, the Sweep with Twist option may perform a bit better with pre-distortion to compensate for a sweep direction that will be non perpendicular to the profiles normal.

 

For instance, these ellipse shapes sweep to a form closer to circular.

[ReMark]

Yep, I knew it as soon as I pressed the Post Quick Reply button that "Helix" was all wrong so I deleted my post.

 

Sweep with Twist option. Cool! I'm going to go try that right now. Thanks SEANT.

[SEANT]

Yep, I knew it as soon as I pressed the Post Quick Reply button that "Helix" was all wrong so I deleted my post.

 

Sweep with Twist option. Cool! I'm going to go try that right now. Thanks SEANT.

 

To be honest, ReMark, I wasn’t familiar with that process either until mentioned by the OP. I also assumed that lofted circles (with a wrapped helix as a path) was the only viable option.

[kencaz]

As mentioned, the Sweep with Twist option may perform a bit better with pre-distortion to compensate for a sweep direction that will be non perpendicular to the profiles normal.

 

For instance, these ellipse shapes sweep to a form closer to circular.

 

Very nice "SEANT"

[MikeScott]

Well.. I didn't do bad considering I dont have access to the sweep command and never used or seen it used until this thread. Seant definately had better wording for what I was trying to convey though.

 

Fat lot of good that does me.. I'm a theoretical genius, but only theoretically.. in theory at least.

 

What version was sweep introduced? I'm dying to irritate my millworkers with roped frames and stuff, and have been considering an upgrade.

[Cad64]

What version was sweep introduced?

 

Autocad 2007 introduced the Sweep command.

[MikeScott]

Good to know.. thanks

[ica_cici]

...Somewhere I have an Excel spreadsheet formula to create the curve, but now I can't find it.

...The key will be to get the correct math curve for the path at the center of your sweep profile with the profile perpendicular to the path at the start of the sweep.

 

I know nothing about the Excel formula JD Mather,

 

but I made these two spline paths manually (see the picture). It just trial & error. The problem is I couldn't extrude or sweep the circle profile along the path. Should I trace it by 3dpline?

 

Is there a way to turn a spline into pline?

 

 

That's lovely SEANT,

 

I tried what you did, but I don't get the same result as yours. I trimmed the two circles and pedit into pline, then sweep it along the ellipse path using twist angle=3240. So something wrong with my procedure I believe. Wow...

How did you do that?

sweep.dwg

[SEANT]

Instead of circles, ellipses (combined as Regions) were used with the sweep command. See attached

EllipseSweep.dwg

[iskalipsi]

How would you know the Twist angle you will be using?

[ica_cici]

I just multiply total coils to 180 degree. My target is an oval twist with N=18 coils, so 18 X 180 = 3240 degrees.

[iskalipsi]

Nice. Thanks for that info

[ica_cici]

Instead of circles, ellipses (combined as Regions) were used with the sweep command. See attached

 

How did you get the ellipses size (1.44)?

 

 

Nice. Thanks for that info

 

You are welcome.