Drawing Nested Ellipses in CAD

      but not both. Ace CAD drafters share quick ellipse tips. June 28, 2005

I am looking for some help programming the ellipse below in Alphacam. I have tried the ellipse function, as well as stretching a circle. It seems the width and distances given never all agree. Does anyone have any suggestions?

Click here for full size image

Forum Responses
(CAD Forum)
From contributor K:
Only one of the two curves can be part of an ellipse. You should use offset to get the other curve

From the original questioner:
To contributor K: I tried that, but still had trouble getting all of the dimensions correct.

From contributor E:
Using the data from your drawing, I recreated the outer ellipse. I then used offset>distance=4.5>What=geometry

Then by using Dimension>Type=aligned and using snap to end of line/arc, I confirmed a constant margin around the two geometries. Is your goal to make a constant width, or a mathematically correct pair of ellipses?

From contributor R:
Is AlphaCAM really that hard to draw in? It took me took less than 5 minutes to draw this in AutoCAD.

Click here for full size image

From contributor B:
I was able to draw this in 7 Minutes in Mastercam with all the dimensioning and notes. Contributor K is right. You cannot use two ellipses to produce what you are looking for. It’s mathematically impossible.

Click here for full size image

From contributor E:
To contributor R: AlphaCAM isn't that hard to draw in. My sample was done in about two minutes, including dimensioning and reffering back here to confirm dimensions and what the original post requested.

From contributor R:
I’m not sure I understand the message that states it can not be drawn with 2 ellipses. I absolutely can draw it as 2 ellipses in AutoCAD and get the dimensioned results. The original drawing posted looks like it was done in Acad (based on the font).

Would it not be easier to get the .dwg from the source, and use it in AlphaCAM? Can AlphaCAM import the nurbs ellipse from AutoCAD, or does it require the pellipse set to 1?
Does anyone know if AlphaCAM can read the new 2004-2005 dwg format (or does it require to be saved as 2000 compatible)?

From contributor B:
To contributor R: Take a look at the drawing below, and then tell me if you can create the two ellipses in AutoCAD and also maintain the same width of 4.5" along the length of the part. Yes, you will be able to achieve the 4.5" at the four quadrants (), 90, 180, 270 degrees), but the width will vary in-between the quadrant locations.

Again, in order to create the required geometry, one must create the base ellipse and then offset it by 4.5" to create the necessary oval shape (made of a spline, nurbed curve or line/arc approximation).

Click here for full size image

From contributor R:
To contributor B: Thank you. I see your point that if I use the nurbs ellipse and offset it, the offset object is a spline. The variance between an ellipse and a spline appears to be under .06 inches in most places for this example.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Computerization

  • KnowledgeBase: Computerization: CAD Computer Related Design

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2019 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article