Exercise 217

Unrolling Surfaces & Watertight Objects

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In this exercise, you will work to make unrolled surfaces that when cut out will create a physical model of your skyscraper. If you can, please try to work with the skyscraper you created on Wednesday. If you find the tower to difficult, you may break it into parts or redesign/simplify your tower.  You will also learn how to create a watertight model for 3D printing and export a .obj file.

Part 1:

  • Go over your model, try to make as few surfaces as you can (this will simplify the unroll). Use the “join” command when possible to make polysurfaces.
  • Use the unrollsrf command (Rhino 5.22 [Unrollsrf]) making sure to turn the labels “on” as well as explode to “yes.”
  • In the top view, arrange your unrolled surfaces with numbered sides matching each other. Try to combine sides where possible to create a foldable cutout of your skyscraper.
  • Use the Curve>Curve From Object>Duplicate Border (dupborder) to make laser-cut lines for your shapes. Use the Offset command to create “glue tabs” to put your shape together. Remember to make cut lines red and engrave lines blue.
    • Note: You will not actually cut out this model, but the design here is that you could cut it out if it was assigned. Take some time to really learn this skill as you will use it in future classes (Archi 221 for example).
  • Make sure to include the top and the bottom of your skyscraper as this will help you to create your final shape.

Part 2: (Watertight model)

Select your building’s skin and core.  Use File>Export Selected... to export a new Rhino .3dm file for preparing your 3D print file.

Make sure each object in your building is a closed polysurface.  To check this, type showedges in the command line and check the radio button for “Naked Edges.”  If you see any edges highlighted, your model is not watertight and you should add an appropriate surface and join the surface into a closed polysurface.  (This will be demonstrated in lecture)

Next, you will need to scale this model so that 100’ = 3/4” (if your model is 804’ tall, it should be 6.03” tall at scale.  If your model is 600’ tall, it should be 4.5” tall).  Move your newly scaled object to 0,0.

Type mesh into the command line and select your entire model.  Adjust the polygon count to an appropriate number for your model (use the Preview button to see what your model will look like).  You will now need to delete your NURBS objects.

Right click on “inches” at the bottom of the screen and select “Unit Settings” from the popup.  Change your units to Millimeters and choose to scale your model by 25.4 when prompted.

With your model selected, navigate to File>Export selected.  Choose OBJ (*.obj) as the "Save as Type" and click “Save.”  The default options are fine.  This file is now ready to generate gcode and 3D print.