First Success

21 10 2008

Check this out. A truncated dodecahedral Polywell rendered in CAD.

I created this using ruby to pass draw instructions to mged (the main command line tool for BRL-CAD):

require 'matrix'
phi = (1+Math.sqrt(5))/2
icosahedron = Matrix[
[0, +1, +phi],
[0, +1, -phi],
[0, -1, +phi],
[0, -1, -phi],
[+1, +phi, 0],
[+1, -phi, 0],
[-1, +phi, 0],
[-1, -phi, 0],
[+phi, 0, +1],
[+phi, 0, -1],
[-phi, 0, +1],
[-phi, 0, -1]

icosahedron.row_vectors().each_with_index do |v,index|
`/usr/brlcad/bin/mged -f -c test3.g 'in torus#{index}.s tor #{v[0]} #{v[1]} #{v[2]} #{v[0]} #{v[1]} #{v[2]} 1.0 0.125'`

This basically iterates through the vertices of the icosahedron, and draws a torus normal to the origin. Now we are tantalizingly close to having a CAD file we can render in metal.


21 10 2008

First off, I’m all about open source software. Free, unencumbered, agile, fast.

For CAD I’m using BRL-CAD which is based on constructive solid geometry

For glue code I’ll use Ruby or Python. I know ruby I don’t know python.

SAGE for a mathematics package.

I havn’t looked closely at this yet, but here is a list of robots software packages

My laptop is a mac, I use linux on the server side, and will likely use EC2 for cloud computing.

Fabrication Technology

21 10 2008

This is my favorite part.

Lets start with Direct Metal Deposition. This video breaks it down:


This approach can create fully melted seamless structural elements out of stainless or tool steel. Incredible! I see using this for the structural elements such as the walls of the core.


For delicate welding there is electron beam welding. EMC used this to weld the toruses without damaging the the coils inside.


For an additive process with a fine structure we have  Electron Beam Melting. Here is a cool pic from Arcam’s brocure:

Electron Beam Melting

Electron Beam Melting

However this approach requires 1) a level work surface 2) high vacuum 3) covering the work surface with metal powder. Arcam’s current size limit is 200mm X 200mm X 350mm, so too small for the core. However the technology could possibly be adapted for a larger format. I image EBM could be used to fabricate superconductors in-situ (wild speculation, more later).

Finally, we have old fashioned robotic milling, as featured recently in Apple’s making of the macbook video:

Robotic milling and polishing allow you to achieve high tolerances and high finish even while using an additive process like Direct Metal Deposition.

What is so exciting about these fabrication technologies is that taken together they allow for a direct to metal workflow. A CAD file goes in one side and a finished product comes out the other (with hours of WTF in-between).

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