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  1. #1
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    Default Chordal Tolerance/Triangular Deviation

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    At my workplace, we draw small 3D positives in AutoCAD and have SLA positives made. From these SLA positives, we make silicone molds. Anyhow, the SLA company sent an e-mail and I can't figure out how to adjust what they are saying. """ I have attached a JPEG File depicting coarse features in your files; due to the fact the parts are not large this will be not pose a problem, but as the parts get larger the surface coarseness is more noticeable. You can increase your surface resolution by increasing your setting for chordal tolerance height or it may be called triangular deviation to 0.001 inch when the STL file is exported from your CAD program """. Anyone familiar with the Chordal Tolerance settings? How about Triangular deviation? A co-worker who draws most of these positives can not find these settings in AutoCAD and we need help. Any assistance would be appreciated.

    Brian

  2. #2
    Quantum Mechanic ReMark's Avatar
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    “Chordal Tolerance numerically describes the maximum distance between the actual part surface and the tessellated surface of the STL file.”

    Referenced from: http://fstroj.utc.sk/journal/engl/papers/036_2002.pdf

    It sounds like you may have to increase the default values on such parameters as isolines, surftab1, surftab2, etc. to get the desired result the SLA company is seeking.

    I too could not find any reference to chordal tolerance or triangular deviation within AutoCAD.
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  3. #3
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    Addendum:

    This might help too:

    < start quote>

    DISPSILH
    Show Silhouettes in Wireframe

    Controls whether silhouette curves of 3D solid objects are displayed as wireframes. This option also controls whether mesh is drawn or suppressed when a 3D solid object is hidden. This setting is saved in the drawing. Clear this option to optimize performance.

    The value is also controlled by the DISPSILH system variable.


    ISOLINES
    Contour Lines per Surface

    Sets the number of contour lines per surface on objects. A higher number decreases display performance and increases rendering time. The valid range is 0 to 2047. The default setting is 4. This setting is saved in the drawing.

    The value is also controlled by the ISOLINES system variable.

    <end quote>

    The above comes courtesy of AutoDesk Discussion Groups.
    Last edited by ReMark; 8th Feb 2007 at 12:29 pm. Reason: sloppy copy/paste technique...my apologies
    "I have only come here seeking knowledge. Things they wouldn't teach me of in college." The Police

    Eat brains...gain more knowledge!

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