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Modeling a curved surface &  #3dScanning and scanner post processing

Posted on September 29th, 2015

#Solidworks users groups of New York City @swugnyc

09/29/2015 @ Huge, 45 Main St, Brooklyn, NY

Val Angelov walked through the modeling of a hinge for an antique car and Arthur Spivey talked about lessons he has learned about post processing 3d scans.

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Val Angelov gave practical tips for surface modeling illustrated by a walk through modeling a hinge. He started from a rough block model specifying how the part should fit on the car and gradually replacing blocked surfaces with curves.  Advice included:

  1. You will need to hold onto some part of the part, so start there
  2. Take advantage of symmetry
  3. Minimize curvature change along the edges- first cut into sections then fit each section
  4. Avoid small surfaces and tight corners
  5. Revisit problem areas

Val then demonstrated how he designed the hinge:

  1. start with a solid piece with the overall split into sections
  2. split in half, do one side then mirror it over
  3. delete parts of the surface and replace them with new curved surfaces
  4. use boundary or loft to make sure surfaces mesh together smoothly
  5. use zebra stripes to see if the surfaces are continuous.

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In the next talk, Arthur Spivey covered a wide range of topics on post processing the meshes from scans. He described the wide range of tools he uses and emphasized that you need to consider what you intend to do with the scan. The answer leads to the cost of the software, the number of tools you need to master, and the time invested.

Some of his comments were

  1. The NextEngine scanner is cheaper than Lidar, but still gives good results
  2. Meshlab is a good tool for viewing stl files (its also open source)
  3. There are many scanner technologies (laser, white light, …), but all will struggle to scan glass or metal objects
  4. Geomagic can display a point cloud and has tools for you to patch holes: either matching nearby curvature or using the tangent. It can also bring together multiple meshes and map out a best consensus (you need to identify at least 3 points that line up on the two meshes). There are further cleanup tools, such as one that remaps intersecting triangles.
  5. Importing an stl file as a surface body (instead of a graphics body) allows you to manipulate the image
  6. Other useful tools include Blender, Zbrush, Rhino, Modo, and Meshmixer. Each has its strengths and capabilities. Rhino, for instance, is excellent at flow log surfaces (take a surface and wrap it around a body). Modo maps mesh triangles into quadrangles. Quadrangles are easier to manipulate when making changes to the surface.

He concluded by talking about when to use mirroring to take advantage of surface symmetry and when not to use it. The downside is that creating half and mirroring it is that the object a seam where the parts join, but a seamless tube is often more conducive to further editing.

posted in:  3-d printing, 3-d scanning, Open source, Solidworks    / leave comments:   No comments yet