Rhino X shape smooth modelling

Discussion in 'Software' started by Guinther, Jun 1, 2011.

  1. Guinther
    Joined: Jun 2011
    Posts: 6
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    Location: Brazil

    Guinther Junior Member

    Hey guys,

    I was wondering if you can help me with an apparently easy problem. I am modelling a flat surface with an X shape poping up in the center and fading away on the ends. The X shape must be smoothly connected to the plate. I have been trying everything I can, and there is always some surface unmatched.

    Check the attachment, you will see what I am talking about. I have tried, matchsrf, blendsrf, networksrf, tsskin... but the result is never satisfactory, considering that this will be a mold. Please if you know a way to solve this problem, let me know.

    Regards,

    Guinther
     

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  2. Tim B
    Joined: Jan 2003
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    Location: Southern England

    Tim B Senior Member

    If you just want sloping edges and radiused corners, then generate two outline Xs one slightly smaller than the other and build surfaces and fillets as required. If you want a "sheet draped over an X" effect, build an X, then use the drape tool to apply a surface over it.

    Hope this helps,

    Tim B.
     
  3. Guinther
    Joined: Jun 2011
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    Location: Brazil

    Guinther Junior Member

    Thanks Tim!

    Indeed I need the sheet draped over an X effect. I've been trying the drape tool for a while, but the results always lack precision and the surface is not smooth. I tried to tweak a bit the spacing, but no success. But thanks for your reply anyway.

    Regards,

    Guinther
     
  4. quequen
    Joined: Jul 2009
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    Location: argentina

    quequen Senior Member

    Here some bad tryes... you should try using nurbs and modelling all the shape at once, no arrays...
    Another way is to perform level curves like waterlines, then cover them with a surface...
     

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  5. Guinther
    Joined: Jun 2011
    Posts: 6
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    Location: Brazil

    Guinther Junior Member

    Thanks quequen!

    My first approach was to model it out of one surface. But it turned to be too hard to do it so. Especially keeping the precision and symmetry. I did try the level curves, with tsskin, and the result was not very precise. It loses some important details.

    I think the hardest part is where the 'legs' merge into a single object. The discontinuity that you had at those points on your file, is the same that I've been having for quite some time. I have applied some matchsrf there and I got some good results. I'm not quite there yet, few some adjustments are needed.

    Thnx anyway man,

    Regards,

    Guinther
     
  6. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    This is how I did the homework:
    • Picture 1 - create the section curve (in my case a half-circle) and a rail perpendicular to it (in my case a line).
    • Picture 2 - create a surface by sweeping the section curve along the rail (I've used the "Sweep 1 Rail" command).
    • Picture 3 - create a polar array of 4 surfaces (Polar Array command); note how they are intersecting on the underside - you have to trim these intersections.
    • Picture 4 - eliminate the protruding parts with the Trim command.
    • Picture 5 - the 4 surfaces are now ready for filleting
    • Picture 6 - use the "Variable Fillet Surfaces" command to smoothly join them along the intersecting edges; you can play with the bottom and top-end radiuses to obtain the result you prefer. I have used R=0.1 at the bottom and R=0.05 at the top.
    • Picture 7 & 8 - as you can see, the surfaces are smoothly blended with each other.
    Hope this will help. Cheers! ;)
     

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  7. Guinther
    Joined: Jun 2011
    Posts: 6
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    Location: Brazil

    Guinther Junior Member

    Thanks daiquiri!

    I have tried this approach as well. Although the result is close to what I need it is still not quite it. The blending is very good, but it becomes more complex when you add one more radius where it blends with the sheet, to give the draping effect. The top also needs to be smoother, meaning that the blending between the 'legs' needs to go until the top.

    I made some improvements on how it should look. It still needs some changes, but I am going to build a small scale mold this week, based on this last file, to see how the CNC will read all the small imperfections.

    Thanks for the reply.

    Regards,

    Guinther
     

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