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titleConsiderations for this method

The horizontal topo model making method produces various degrees of detail depending on the thickness of the material.

Assembly can be time intensive but there are tricks to make it faster: using spray mount or a staple gun instead of glue speeds up the assembly process. It can also require a large amount of material which is expensive and makes for a heavy model; cutting out the non-visible insides of the layers and nesting smaller layers within them can help (see topic: Clear Casting Resin Alternatives: Golden Acrylic Leveling Gel).

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PROS:

  • Resilient once cured
  • Can be colored with special pigments

CONS:

  • Incompatible with some materials (chemically inhibiting the curing process)
  • Requires degassing in vacuum chamber for maximum clarity
  • Mixture ratio 10:1 must be carefully measured

 


Material options

 METHODMATERIALCOST ($/sf)TIME: file prep (hr)TIME: fab (hr)TIME: assembly (hr)cubic inch)TIME: totalMATERIAL RECYCLABILITY
Image RemovedHorizontal laser-cut topo - 25 layers1/16" chip with plywood base$30851023yes
Image RemovedHorizontal laser-cut topo - 25 layers4ply museum$62851023yes

 

 

File preparation

You'll need a file with horizontal contour lines at a vertical spacing that matches the thickness of your modeling material.
If your base file contains contours at a different resolution, use the RhinoTerrain plugin (available in the Software folder on Goliath) to make a 3D mesh from the given contours.
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You can either:Contour the mesh and the buildings together,Then clean up the resulting contour curves (delete building contours which are below the surface of the topography, and remove topography curves which are inside buildings).
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Or, use the drape command to create a NURBS surface from the topography mesh,
  • Then use the buildings to make holes in the new NURBS surface,
  • And use the new NURBS surface to trim away the subterranean parts of the buildings.
    • Then contour it all together. By trimming the surfaces, you avoid having to trim the contours as in option (i).
    Put the resulting contours on your CUT layer, then copy them up (along the positive Z axis) one level. Put the copies on your ETCH layer.
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    Lay out each layer pair (one CUT, one ETCH) on laser bed-sized (18" x 32") sheets of material. Small layers can be nested inside larger ones to save material.
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    1. Label your sheets to keep track of stacking order. 

    Making the model

    1. Prepare material for the number of sheets you will need to laser cut. 
      1. If buying material from the GSD Store, it will already be cut to the laser bed size.
      2. If buying material from other vendors, you most likely will need to cut material to the laser bed size (18" x 32").
    2. Always test cut a small piece first to make sure that the laser is cutting the material through all the way. The edges of the cut sheets will be very visible, so use as low of a PPI setting as possible to minimize burning. 
    3. Once all sheets have been cut:
      1. Stack layers in order, aligning the top layer to the ETCH of the bottom layer.
      2. Glue layers together 
        1. Spray mount adhesive works best for fast assembly.
        2. Only spray on the bottom (non-visible) side of each layer to avoid messy craftsmanship.   

     

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    Related issues 
    Production StepsTime requiredSpecial Equipment NeededConditionsAble to be colored?health and safetyChemical CompositionPPEWhere to Purchase

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    		Without Vacuum ChamberSORTA-Clear 40$0.8016.5 hours (30 minutes preparation and 16 hours cure time)Measure each component of the 2-part product into mixing container as specified by manufacturer's instructions.
    Stir thoroughly to combine two components.

    Pour into the lowest point of the model/mold to avoid trapping air bubbles. A thin stream poured slowly from high above may help to remove small air bubbles not collapsed by vacuum chamber.
    Allow 16 hours for substance to cure before handling.    		Pot life is 60 minutes. Cure time is 16 hours, regardless of volume. Curing can be accelerated by applying mild heat (up to 60º C). PRODUCT WILL DARKEN CONSIDERABLY IF HEATED.Scale to measure the two components by weight accurately.
    Large, clean mixing container and stir stick.

    		Product is a platinum-cure silicone rubber, and is incompatible with materials bearing platinum-cure inhibitors. Will not cure if ratio of two components is not accurately measured.Yes.
    Add a small amount of Silc Pig™ color pigment to Part A and mix thoroughly before combining with Part B.    		Part A: No data on possible toxicological effects available.
    Part B: No data on possible toxicological effects available.    		UnlistedVinyl gloves to limit skin contact, splash goggles to prevent contact with eye.
    (latex gloves will inhibit cure of the product)    		Reynolds Advanced Materials

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    		With Vacuum ChamberSORTA-Clear 4017 hours (1 hour preparation and 16 hours cure time)

    See above, after measuring and mixing the two components, degas the mixture using a vacuum chamber. (Mixing container must be at least 4 times the volume of the combined components, as the gas expands and may over-flow the container.)

    Then follow remaining steps, above.

    		In addition to above, a vacuum chamber to degas the mixed substance before it is poured into mold/model.

     

     

    Mold preparation