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Thread: drawing nano tubes

  1. #1
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    drawing nano tubes

    hi....i m samee...a new member of this forum....i m having some difficulties in drawing some extremely small objects in autocad...hope u guys can help me...

    i need to draw a hollow cylinder of internal radius of 4.6 e -9 and external radius of 5 e -9 and height of 100 e -9...but apparently autocad finds it difficult to deal with such small object...what could be the possible solution?

    thnaks in advance

  2. #2
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    Autocad can draw anything from the head of a pin to the entire earth. What exactly is the problem you are encountering? How is Autocad reacting?

    I'm not familiar with the dimensions you posted. 4.6 e -9? What is that, Scientific?
    One of these days I gotta get myself organizized

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  3. #3
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    I recall that AutoCAd can deal with decimals to 16 places, or 10 e-16. So I would think that e-9 would not be a problem. When working in very large coodinates (say over 10 e6) AutoCAD has problems with accurate offsets & hatching, maybe something similar happens when at very small coordinates. Just what difficulties are you having?

    A problem you might find is that AutoCAD reports to the command line to at most 8 decimal places, so anything smaller such as your would show as "0.00000000" even though it does havea (smaller) dimension.

    Another option is to just drop the "e-9" when you draw it - effectively scaling it by e9.

  4. #4
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    I think that Carl has got this one, you need to make sure that you have set the prescision to cope with the units that you are using.

    I am also not sure that Autocad will recognise the scientific notation "e-**"

    As proposed if all the denominators are at the same factor then forget the "e-**" and just use the base figure.

    (forgive the spelling I've had a few beers; it is christmas eve)


  5. #5
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    actually i have to draw a cylinder with radius 5e-9 and height of 100e-9.

    but when i try to give input the radius it says the radius must be nonzero and positive. same thing happens for the height.

    i have to draw it to the exact dimension so that i can export the drawing as *.sat format to use in another program

    @newcad: how to set the precision?

    thanks in advance

  6. #6
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    Make sure you turn off your running osnaps (F3) or these small distances will be within the snap aperture & thus (probably) the zero-length message.

    Set precision in Format>>Units>>precision; or with the LUPREC setting/command.

  7. #7
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    A lot of people get confused with what 1 unit in autocad is equal to. Well, it's equal to what every you want it to be.

    SOOOOO,

    Why not just use autocad as if 1 drawing unit = 1 nanometer? That way you don't have to type so much or struggle with software limitations.

  8. #8
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    Quote Originally Posted by VERYCIVILDRAFTER View Post
    A lot of people get confused with what 1 unit in autocad is equal to. Well, it's equal to what every you want it to be.

    SOOOOO,

    Why not just use autocad as if 1 drawing unit = 1 nanometer? That way you don't have to type so much or struggle with software limitations.
    this

    if you need to, you can scale via view ports

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