O/T - Creating a CAD file from a simple template? - Page 2
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  1. #21
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    Quote Originally Posted by Joe Gwinn View Post
    If it's an airfoil, it will be described by a relatively simple equation that generates all the surface location points. It will not be described only as a point cloud.
    Uhm no, not yet it won't.

    It appears the template is from something "developed in the field" and now needs
    now needs measured, to make a part, or "derive that equation".

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    Quote Originally Posted by Joe Gwinn View Post
    If it's an airfoil, it will be described by a relatively simple equation that generates all the surface location points. It will not be described only as a point cloud.
    Never did this but always wanted to : APT can do that directly. And APT is in the public domain, it's free

    The only bad part is, he'd have to know the equation that determined his arc ...

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    If you measure a bunch of points manually and put them in Excel you can probably do a decent polynomial fit to get an analytic expression for most of the curve. It was thinking after my last post that doing it that way would be nice because if you wanted to redesign and optimize it you'd want to start with equation driven curves.

    OP if you attach a file with measurements every .1" or so we can all monkey with it. Gotta do something in the run up to New Years!

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    Nb I just went away and made an NACA2215 airfoil using an online calculator. I exported 100 points and made a Curve Through XYZ points in Solidworks which works perfectly once you futz around with the file in Word and Excel to get the proper space delimited text file with the columns mapped to the correct XYZ axes. I still think here you want a polynomial approximation but the curve thing here works well.

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    OK, I've entered a bunch of individual points for the top side, I realize now I should have used the line command and drawn a line from point to point.

    Been Googling for an hour, any way to join the points into a smooth line?


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    Do have a draw option in the menu? In my old dinosaur CAD (Design CAD 2D for DOS) which I still use I would select DRAW then CURVE and then connect the dots.

    If you can not find another way with your CAD, I could do it in mine then convert to DXF for you.

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    Thanks for the reply. When I select any of the Draw commands (line, polyline, circle, arc) it's looking for an x-y coordinate, it won't let me select my existing points...

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    Quote Originally Posted by Terry Keeley View Post
    Thanks for the reply. When I select any of the Draw commands (line, polyline, circle, arc) it's looking for an x-y coordinate, it won't let me select my existing points...
    Type in "OSNAP", and youll'be presented with a window for Object Snap settings.
    Check the "Object Snap On" box, check the "Node" box and uncheck all others.

    Now you can just type "SPLINE" and then click away at each point, the cursor will "snap" to points and points only, but make sure to do it in the proper order otherwise you will have to start over.

    Oh, If I were you I would put the points on one layer ( say Layer0 ) and the spline on a different one, that way if you do screw up it will be much easier to delete
    the spline or add other points.

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    Quote Originally Posted by SeymourDumore View Post
    Type in "OSNAP", and youll'be presented with a window for Object Snap settings.
    Check the "Object Snap On" box, check the "Node" box and uncheck all others.

    Now you can just type "SPLINE" and then click away at each point, the cursor will "snap" to points and points only, but make sure to do it in the proper order otherwise you will have to start over.

    Oh, If I were you I would put the points on one layer ( say Layer0 ) and the spline on a different one, that way if you do screw up it will be much easier to delete
    the spline or add other points.


    You're awsome, I've been looking for that for hours, thought I needed the Spline function but couldn't figure the Nodes part.

    I owe you a beer!

  11. #30
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    I got the side profile drawn thanks to some help from Seymore but I screwed up and didn't rotate the UCS before starting. Now if I extrude it along the Z axis it gets "tall" instead of "wide". If I did it right the drawing would have been on the "wall" instead of the "floor".

    I think I need to use UCSFOLLOW = 1 but I can't get the drawing to rotate about the x axis.

    Any ideas?



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    Quote Originally Posted by digger doug View Post
    Uhm no, not yet it won't.

    It appears the template is from something "developed in the field" and now needs
    now needs measured, to make a part, or "derive that equation".
    Lofting used to be done with a full-size drawing on an aluminum sheet painted white. This traditional approach collapsed under the pressures of WW2, leading to the mathematical approach.


    See "Aircraft Analytic Geometry: Applied to Engineering, Lofting, and Tooling", J. J. Apalategui (Author),‎ L. J. Adams (Author); McGraw-Hill 1944, 285 pages. See chapters 10 and 11 for the math.

    Aircraft Analytic Geometry: Applied to Engineering, Lofting, and Tooling: J. J. Apalategui, L. J. Adams: 978112411453: Amazon.com: Books

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    Quote Originally Posted by Joe Gwinn View Post
    Lofting used to be done with a full-size drawing on an aluminum sheet painted white. This traditional approach collapsed under the pressures of WW2, leading to the mathematical approach.


    See "Aircraft Analytic Geometry: Applied to Engineering, Lofting, and Tooling", J. J. Apalategui (Author),‎ L. J. Adams (Author); McGraw-Hill 1944, 285 pages. See chapters 10 and 11 for the math.

    Aircraft Analytic Geometry: Applied to Engineering, Lofting, and Tooling: J. J. Apalategui, L. J. Adams: 978112411453: Amazon.com: Books
    No need to school me.

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    Terry

    I am still not clear on what you intend to do, but if all is needed that the initial point pattern is on a different plane, just select
    the appropriate view ( left, right, top etc ), select the entire solid ( window select if not a block ) then click "Rotate", pick the point about which
    you want the rotation and type in 90 deg.

    But again, not knowing exactly what you need, if your spline is of the correct shape and size, then all you need is to extrude to the length.
    If it's let's say a 1/8" sheet, just type "extrude", select the closed profile and type in .125 for the extruded length.....

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    Quote Originally Posted by SeymourDumore View Post
    Terry

    I am still not clear on what you intend to do, but if all is needed that the initial point pattern is on a different plane, just select
    the appropriate view ( left, right, top etc ), select the entire solid ( window select if not a block ) then click "Rotate", pick the point about which
    you want the rotation and type in 90 deg.

    But again, not knowing exactly what you need, if your spline is of the correct shape and size, then all you need is to extrude to the length.
    If it's let's say a 1/8" sheet, just type "extrude", select the closed profile and type in .125 for the extruded length.....
    Again, thanks for the help.

    The rotate command seems to rotate the object about the Z axis, I need to rotate it about X.

    In the SW Isometric view on the right in post #30, I want to make what's now the top the front and the front the bottom (as shown by the square at the top right).

  17. #35
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    Quote Originally Posted by Terry Keeley View Post

    The rotate command seems to rotate the object about the Z axis, I need to rotate it about X.
    Terry


    Then go to the left or right view and select the objects to rotate.
    Yes, ACAD is dumb and it will show you X/Y as the axis on the UCS, but in the real space you will be rotating about the X.

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    Got it, thanks for the help!




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