Polar Array

[Anonymous]

I have created a parabola with 100 line segments (importing them with a script) on the XY plane.  I want to replicate said parabola on the Z axis to create a bowl, but despite trying all possible permutations and redrawing the parabola to be sure that one of the line segments ends in the point (0,0) at the mid point of the parabola, I get double sets, with one of them 0.005 units off (the parabola dimensions are 200 units) which looks ragged.   Any suggestions?

[JDMather]

Why are you using lines rather than a Spline?

Your "curve" is not centered.  You made a mistake in creation.

(see attached)

What is your design intent for this?  (looks to me like it would be a Revolve rather than an Array)

[Anonymous]

Hi JDMather,

Thanks for the reply. 

I am working on a parabolic dish solar concentrator - I can create many different shaped mirrors, incident rays, reflected rays, etc, and create a scrip file that draws a ray diagran in Autocad.  It was easy to draw a line.  It might be possible to do it with spline, but so far I was happy with my results.  

Before I restore to seeking help, I tried anything that I could imagine.  One mirror had one line at (2,0.005) and I used that as my rotating point; I created another mirror that touched (0,0); I changed the associative property, modify the array and the distance between rows and lines, the rotation of the piece and anything that I could think. Tried defining the z axis of rotation, in one plane and another. 

sometimes even the parabola inverted itself and create a circle in the center(?).

Interestingly enough, a previous version (2007) on my portable with XP with an educational program, produces the results that I want.  I am doing drawings for a patent application and the educational border is not acceptable.

Even if the curve was not centered, it should rotale and have one edge lower than the other.  I just tried revolve and it is nor producing the paraboloid that I am seeking.  

Could not open your attachment.   It was created with a newer version than mine. 

Any more suggestions?

Thank you again for your help.

eduardo

[JDMather]

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@Anonymous wrote:

Could not open your attachment.   It was created with a newer version than mine. 

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Saved down to earlier version.

[Anonymous]

Hi JD Mather
Thanks for your replies and resending the file. 

I send a drawing from Autodesk 2005 showing what I wanted to do.  It works as expected.  Unfortunately it did not made it here and I can not resend until Monday morning.   

The following parabola is symmetric.  it starts at (-400,40), has one point (0,0) and ends at (400,40).  The outcome of rotating it defining the point (0,0) is shown in the attached file. 

The ragginess bother me completely.

[JDMather]

I don't understand the design intent -

why use little lines?

Why not model as solid (like the real world)?

Looks like a simple Revolve rather than an array to me, but as I've stated, I don't really understand where you are going with this.

[Anonymous]

Hi JDMather,

Thank you for your perseverance and help.

Several reasons for your questions:

(1) calculations of ray diagram to define optimal shape;

(2) quick tool to see it on the screen, and;

(3) patent drawings have specific drawing requirements, no solids.

As I mentioned in an e-mail that never made it to the site, in Autocad 2005,
it works (I even sent you a drawing showing what I wanted). Unfortunately,
that is an education version and the educational banner complicates life. I
would have presumed that polar array would work as intended in Autocad 2012.


the pertinent portion of the notepad file to create the original mirror is
attached.

>From what I can deduce, Autocad is doubling the number of items count that I
am asking and spacing the rows and columns somewhat. even when I had change
the spacing to 0, I still get the duplicated offset. Do I have a problem
with options? tolerance? or some other quick fix.

best regards

eduardo



Eduardo Saucedo
900 Stone Falls Trail
Raleigh NC 27614
(919)-847-1361
(202)-437-6008 (cell)

[JDMather]

(3) patent drawings have specific drawing requirements, no solids.

The real world is 3D solids.  AutoCAD will create 2D drawings from 3D solids.

I would be using Autodesk Inventor for something like this with the illustration render output.

[Anonymous]

Hi JDMather,

If I understand you correctly, there is a glitch with Autocad and the best
work around is using something else. As you stated, the real world is 3D,
but for many years we have to put up with 2D limitations because paper is 2D
and there were drawing limitations. Even for Autocad, it took many many
years to come up with a half decent 3D software that continues to improve.

I do have Inventor, courtesy of Autodesk for start-ups. I know that
Inventor can translate something into Autocad 2D.

Unfortunately, the USPTO, is still stuck in the past and does not know about
the real world. I will continue to try to find a way of solving my problem.


thanks a lot for your help.

eduardo



Eduardo Saucedo
900 Stone Falls Trail
Raleigh NC 27614
(919)-847-1361
(202)-437-6008 (cell)

[JDMather]

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@Anonymous wrote:
Hi JDMather,

If I understand you correctly, there is a glitch with Autocad....


Unfortunately, the USPTO, is still stuck in the past and does not know about
the real world.

---

What follows (for whatever it is worth) is opinion only.

You don't understand me correctly.

I don't think there is a "glitch" with AutoCAD, I think the problem is most likely with your understanding of AutoCAD.

And using any CAD or graphics program is irrrelevant to the problem as far as the USPTO is concerned.  The deliverable to them is paper, and even if 21st century digital - could be put in any digital form that their requirement would specify.  This is not a software problem. 

Notice that I am the only one who has responded to this thread.  That is often an indication that the problem statement is not well defined.

I recommend doing "the best you can" and then turn over your art to someone experienced with producing USPTO spec art.

[SEANT61]

I do see a misalignment between geometry and the polar array center point.  Also, the arrayed geometry should only be half of the parabola to avoid overlap.  See example of array in attached.

I have to agree with JDMather, spline based Surfaces/Solids would be the better method for modeling geometry such as this.  Derive 2D drawings from that.

[Anonymous]

Hi JDMather, Seant61

Again, many thanks for sticking with me. 

I have created a smallish parabola, consisting of three lines connecting point (-3,0.0225), (-1,0.0025), (1,0.0025), (3,0225) in the XY plane.  Went to the Z plane, selected all, and made a polar arrar with 120 items rotating around the point (0,0) and it works as expected. 

The larger parabola (the one on the script file that I sent) has 101 points, from (-400,40) to (0,0) to (400,40), but when I rotate it again with a 120 count around point (0,0) I get the perplexing results. 

I obviously do not know AUTOCAD well enough.  That is why I am reaching to you "gurus" for help.

best regards,

eduardo

[Anonymous]

Hi Seant,

Thanks,

I can not open your file.  Too new for my 2012 version. 

I have been careful with geometry and polar array center.  I now have 101 points (one is 0,0), 100 lines, symmetric. 

eduardo

[Anonymous · Accepted solution]

HI JDMather, Sean61

Thanks for your efforts.  I've solved the problem by cutting the parabola in half, starting from point (0,0) to the extreme.  I created a polar array defining the axis as (0,0) and voila!, I got what I wanted without the extra line a bit off center.  Then I used the full parabola, use (0,0) as the axis, select the same number of items, but only rotate it 180 degrees.  Voila! 

For me, I am happy and I am moving forward.  Again, thanks for the interest. 

It was puzzling.  I looked at symmetries, was sure to transfer the figure to touch (0,0) and even got sure to include that point and still got the double line. When I tried with a 3 line segment, it worked.  It worked in the version at the university (Autocad 2007), but not in 2012.  I really thought that the spacing between lines, column was what was causing the problem.  I am happy that I found a way around.  

If another poor soul struggles with it, the advise I would give him would be to be sure that the angle of rotation does not superimpose on the figure.

Best regards,

keep on with the good work.  It is reassuring to know that there is a group of people willing to help others.

eduardo

[SEANT61]

Well, it sounds like you are off and running with the project already, but here is a similar file saved to ver. 2010.  The purpose of the file was just to demo the various ways of representing a parabolic dish. 

I can see how you would prefer your current format - given other scripting assets avaialble - but if you subsequently desire a higher degree of geometric accuracy, the spline based modeling techniques may be just the thing.